Bio-Based Impact-Resistant Materials: Luffa Sponge as a Sustainable Solution

Bio-Based Impact-Resistant Materials: Luffa Sponge as a Sustainable Solution | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Bio-Based Impact-Resistant Materials: Luffa Sponge as a Sustainable Solution Yuanzheng Lin, Chaobin Yang, Zhiyang Pei, Hengyue Xu, Yu Zhang, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6367914/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 17 Nov, 2025 Read the published version in Communications Materials → Version 1 posted You are reading this latest preprint version Abstract This paper develops low-cost, high-performance impact-resistant materials using natural luffa sponge as reinforcement for cementitious composites. It is the first to investigate the effect of temperature on the impact performance of luffa sponge-reinforced cementitious composites (LSRCC) across a wide range from − 196°C to 200°C. Addressing the brittleness of traditional materials at low temperatures, this study pioneers a sustainable, ultra-low-temperature impact-resistant material. Experimental results indicate a strong synergy between the luffa sponge and cement matrix, with the sponge’s networked fibers significantly enhancing structural integrity. Remarkably, LSRCC maintains cohesion under repeated impacts with minimal disintegration. It also exhibits low temperature sensitivity and excellent impact resistance in extreme environments. Interface properties between the luffa sponge and cement matrix were characterized using Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM), supported by Density Functional Theory (DFT) simulations. Results confirm a gradual Interfacial Transition Zone (ITZ) rather than a simple mechanical bond. Simulations reveal that hydrogen bonding within the cellulose matrix drives a gradual variation in the water-to-cement ratio across the interface, resulting in a progressive transition in interfacial strength. This transitional region enhances the load-bearing capacity of LSRCC, highlighting its superior synergistic behavior. Physical sciences/Materials science/Structural materials/Composites Physical sciences/Engineering/Civil engineering Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Impact-resistant materials are crucial for applications where materials must absorb and dissipate energy effectively without significant deforming or failing under sudden impacts ( 1 ). These materials, such as metals ( 2 ), rubbers ( 3 ), ceramics ( 4 ), and polymers ( 5 ), are selected based on specific application needs. Impact-resistant cementitious composite materials have received increased interest due to their advantages ( 6 ). Notably, cementitious composites offer superior durability and longevity compared to metals and rubbers, making them ideal for infrastructure projects that demand low maintenance over long periods. Furthermore, when compared to advanced polymers and ceramics, cementitious composites are more economically viable due to their wide availability and lower cost of cement. For context, the global consumption of cement in 2023 was 4.2 billion tons, exceeding the production volumes of many staple crops, such as wheat ( 7 ). This vast scale of production underlines the accessibility and cost-effectiveness of cement as a raw material. Given these benefits, impact-resistant cementitious composites are extensively used in protective structures, especially in various strategically important infrastructures. For example, they are employed in the construction of nuclear power plants, particularly in containment structures designed to withstand extreme events ( 8 , 9 ). Additionally, these materials are increasingly utilized in water treatment plants ( 10 ), sewer systems ( 11 ), and other facilities requiring durable materials capable of withstanding harsh, corrosive environments. Despite the inherent quasi-brittle nature of cement, which exhibits brittle fractures under tensile and shear stresses, advancements in material science have led to significant improvements in its impact resistance. This is primarily achieved through the even dispersion of various fibers in a matrix, such as steel fiber, polyvinyl alcohol, and polypropylene fibers, enhancing the toughness, strength, and ductility of cementitious composites ( 12 ). These innovations have paved the way for the development of fiber-reinforced cementitious composites, such as Engineered Cementitious Composites (ECC) with ultra-high ductility and Ultra-High Performance Concrete (UHPC) noted for its exceptional strength ( 13 – 15 ). Fibers enhance the impact resistance of cementitious composite by creating a fiber bridging effect that distributes stress across the matrix ( 16 ). However, often these fibers act independently (as they are distributed evenly in the matrix) without forming a unified network, and thus limit the potential for comprehensive impact resistance improvement ( 17 , 18 ). Moreover, traditional fiber-reinforced cementitious composites also exhibit cold brittleness, which is similar to metals and ceramics. As the temperature decreases, their toughness and energy dissipation capacity gradually decline, making them unsuitable for applications in extremely low-temperature environments ( 19 ). Recent research efforts including 3D-printing technology to manufacturing cement-based composites, were made aiming to overcome these limitations by forming integrated fiber networks to improve structural integrity and impact resistance ( 20 , 21 ). However, the implementation of 3D printing technology in this field still faces challenges related to precision, cost, and equipment capabilities, hindering its widespread application. Building upon the technological advancements in cementitious composites, nature itself provides inspiration for impact-resistant materials through the example of the dried fibrous core of the loofah, a plant from the gourd family. The loofah’s fibrous structure is naturally equipped for impact resistance due to its three-dimensional, interlaced fiber network ( 222 , 233 ). This arrangement not only enhances the mechanical integrity and shock absorption capabilities but also aligns with the fundamental characteristics required for impact-resistant materials. Such bio-inspired designs highlight potential avenues for developing advanced materials that mimic these natural structures, offering improved performance and sustainability. Shen et al. ( 244 , 255 ) investigated the basic mechanical properties of luffa sponge and concluded that the luffa sponge was ideal for energy absorption applications as an ultra-light cellular material. The structure of the luffa sponge, characterized by a significant contact area due to its spatially chaotic fiber arrangement, has found successful applications in energy and environmental sectors in recent years ( 266 , 277 ). The morphology and mechanical characteristics of the luffa sponge, as shown in Fig. 1 , reveal various three-dimensional energy-absorbing structural units, e.g., tubular units, fibrous units, and cellular units (see Fig. 1 a). More importantly, the core area of the luffa sponge, which contains coarser fibers, provides a complete support system for the fibers in the outer wall region, thereby enhancing the overall structural integrity under axial load (see Fig. 1 b). Given these characteristics, the impact performance of the luffa sponge stands out within the realm of natural plants, making it an ideal, naturally topology-optimized green energy-absorbing material (see Fig. 1 c). This paper aims to systematically investigate bioinspired impact-resistant cementitious composite materials based on luffa sponge. Unlike the independent toughening mechanism of conventional short-cut fibers in cementitious composites, it is expected that the spatial network structure of luffa sponge fibers can form an integrated toughening system within the cementitious matrix. This study, for the first time, proposes the incorporation of the natural three-dimensional fiber system of luffa sponge into the cement matrix to enhance its toughness and evaluates the performance improvements through impact tests. Building on this, the study first investigates the impact resistance of luffa sponge-reinforced cementitious composites (LSRCC) under ambient conditions, confirming the enhancement in impact resistance provided by the luffa sponge within the cementitious paste. Subsequently, addressing the cold brittleness commonly observed in existing impact-resistant materials, the study is the first to explore the impact performance of LSRCC across a wide temperature range (from − 196°C to 200°C), validating its feasibility as an impact-resistant material for extreme environments. Moreover, utilizing a combination of Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM), the interface transition zone between the luffa sponge and the cementitious paste is characterized at the nanoscale, providing insights into the morphological and physicochemical features contributing to their synergistic behavior. Finally, based on Density Functional Theory (DFT), the interface between cement and the cellulose of luffa sponge was analyzed. The simulation modeled the distribution characteristics of water molecules at the cement-cellulose composite interface, verifying that the hydrogen bonding within the cellulose matrix contributes to the gradual variation in water-to-cement ratio across the interfacial region, thereby leading to a gradual transition in interfacial strength. 2. Results and Discussion 2.1. Characterization of raw materials The basic mechanical and physicochemical properties of cement and luffa sponge are presented in Fig. 2 . The cement used in this study is ordinary Portland cement (42.5R), with a fixed water-to-cement ratio of 0.3. The luffa sponge is derived from the vascular bundles of the mature fruit of the annual herbaceous plant Luffa (from the Cucurbitaceae family), commonly used as cleaning tools or seat cushions. The mechanical and physicochemical characteristics of cement are illustrated in Figs. 2 a through 2 d. Under uniaxial compressive loading, the cement specimens exhibit typical brittle failure, which is why cement or concrete alone is generally unsuitable as impact-resistant materials. The uniaxial compressive behavior of the luffa sponge, as shown in Fig. 2 e, demonstrates notable force plateau and secondary stiffening characteristics. However, its compressive load capacity remains below 1 kN due to the abundant voids within the fiber bundles of the luffa sponge, exhibiting significant deformation with a normal strain exceeding 0.6 (see Fig. 2 f). The microscopic porosity of the luffa sponge, shown in the right side of Fig. 2 f, further indicates that it is not suitable for bearing loads independently. This study explores the combination of cement paste and luffa sponge, utilizing the luffa sponge to enhance the toughness of the cement paste. The production process of LSRCC is illustrated in Fig. 2 g. First, cement is mixed with water to form a paste, after which the luffa sponge is fully immersed in the cement paste. The composite is then cured for 28 days under standard curing conditions (temperature 20 ± 2°C and humidity not less than 95%). Upon completion of the preparation and curing process, uniaxial compressive tests were conducted on the LSRCC specimens, as shown in Fig. 2 h. The test results revealed a significant enhancement in both stiffness and strength in the LSRCC specimens, with peak force reaching 320 kN, exceeding the simple linear addition of the compressive strengths of cement and luffa sponge alone. This confirms the outstanding synergistic effect of cement matrix and luffa sponge in LSRCC. The failure process under axial compression is depicted in Fig. 2 i, where the fiber toughening effect of the luffa sponge significantly improved the brittle nature of the cement paste, resulting in a clear ductile failure mode. 2.2 Preparation and Characterization Following the completion of the axial compressive mechanical performance tests on LSRCC, the impact resistance under ambient temperature was investigated. The CEAST-9250 drop-weight impact tester (Instron Co., Ltd, United States) was employed for this purpose, equipped with a high-speed camera Nova S9 made by Photron (resolution of 1024×1024 pixels, frame rate of 9000 frames per second) to capture the failure process of the specimens, as shown in Fig. 3 a. In this study, the drop weight mass was set at 10.8 kg. Sensors embedded in the drop hammer automatically recorded data during the impact process, including parameters such as force, displacement, and energy. By varying the drop height, different input energies were achieved, specifically 300 J, 500 J, and 700 J, as shown in Fig. 3 b. In addition to varying the input energy, the study also examined the effects of multiple impacts on the cumulative damage evolution of LSRCC. This involved repeated impacts at a constant height, until the specimen was completely damaged, to simulate repeating impact loads that might be induced by mechanical transmission systems on the composite materials. When the impact energy was set to 300 J (drop height of 2820 mm), the failure process of the LSRCC specimen under repeated impacts was captured by the high-speed camera, as shown in Fig. 3 c. The images illustrate the failure characteristics of the specimen at the 1st, 5th, and 9th impacts. From these snapshots, it is evident that although the outer cement paste “protective layer” exhibited early delamination, the core luffa sponge and the encased cement paste maintained perfect synergy. Even after the 9th impact, the overall integrity of the specimen was preserved, demonstrating significant impact ductility. This result correlates well with the axial compressive test findings shown in Figs. 2 h and 2 i. The progressive failure modes of the LSRCC specimens after the 1st to 9th impact loads are depicted in Fig. 3 d, clearly illustrating the damage evolution process. Despite noticeable outer layer delamination and crushing, the luffa sponge and cement paste continued to work in unison, confirming the effectiveness of the luffa sponge’s spatially entangled fibers in reinforcing the cement paste. Figure 3 e presents the force-displacement curves and energy dissipation of the LSRCC specimens under different impact energies and impact counts. Overall, with increasing input impact energy, the peak force and absorbed energy of the LSRCC specimens showed an uprising trend. For a fixed input impact energy, the increase in the number of impacts caused a gradual reduction in peak force, yet the energy dissipation per impact increased progressively. Observing the force-displacement curves, it is apparent that with the increasing number of impacts, the “plateau stage” of the curve became wider. It is inferred that the luffa sponge fibers experience more pronounced delamination and fracture under repeated impact loads, and this “plateau stage” corresponds to the fiber delamination process within the cement paste. Naturally, the delamination and debonding of the fibers contribute to energy dissipation. The impact tests conducted at ambient temperature demonstrated that, thanks to the reinforcing effect of the luffa sponge on the cement paste, the LSRCC specimens exhibited excellent impact resistance. Notably, under repeated impact loads, there was a remarkable increase in the energy dissipation per impact, indicating that LSRCC specimens are highly suitable for applications involving multiple impact loads. 2.3 Environmental Temperature Effects Following the investigation of the impact resistance of LSRCC specimens under ambient temperature conditions, further research was conducted to examine the effect of environmental temperature on their impact resistance. During service, impact-resistant materials inevitably experience temperature fluctuations, and conventional materials often exhibit significant “temperature sensitivity” ( 28 , 29 ). For both cementitious and metallic materials, it is generally observed that as the temperature decreases, strength and stiffness increase, while ductility significantly decreases ( 30 , 31 ). In this study, a drop-weight impact tester equipped with an environmental temperature chamber (Fig. 3 a) was used to perform in-situ high and low-temperature impact tests. For the high-temperature tests, the chamber was set to 100°C and 200°C, and the specimens were placed inside the heating chamber. Once the chamber reached the target temperature, it was maintained for 2 hours before the specimens were removed for impact testing. After each impact, the specimen was returned to the chamber and reheated to the set temperature before the next impact. For the low-temperature tests, the specimens were placed in a dry ice container, ensuring the dry ice fully covered the specimens with a layer of at least 5 cm on both the top and bottom. When the temperature, as measured by the environmental thermometer, reached − 78.5 ± 1°C, the specimens were kept in the container for 5 hours before undergoing impact testing. After each impact, the specimens were returned to the container to cool down to -78.5°C, and immediately after cooling, another impact was conducted. Furthermore, for ultra-low-temperature tests, the specimens were immersed in liquid nitrogen. When the environmental thermometer indicated a temperature of -196 ± 1°C, the specimens were held for 2 hours before being subjected to impact testing. Similar to the previous procedure, the specimens were re-cooled after each impact before the next round of testing. Throughout these tests, high-speed imaging and the sensors embedded in the drop-weight hammer were used to record the impact process. Impact tests were conducted at -196°C, -78.5°C, 25°C, 100°C, and 200°C, with repeated impacts at energy levels of 300 J, 500 J, and 700 J (the input energy at the moment the hammerhead contacted with the specimen). All the energy dissipated by the specimen during each impact and the corresponding peak force recorded by the drop hammer are presented in Fig. 4 a, with additional data extracted from this figure for comparison. As shown, the number of repeated impacts decreases as the temperature increases or decreases for all three energy levels, with the most pronounced reduction observed at 300 J, where the impact count dropped from 9 at 25°C to 3 at both 200°C and − 196°C. In terms of peak force during the first impact, no significant temperature sensitivity was observed for all three energy levels (Fig. 4 b). Similarly, when the energy dissipated in the first impact was normalized by the input energy of the hammer, the energy dissipation also showed no significant temperature sensitivity across the three energy levels (Fig. 4 c). Considering the disintegration of the core matrix as the termination condition, the cumulative energy dissipation of the specimens subjected to repeated impacts at different temperatures and energy levels is shown in Fig. 4 d. At 25°C, the number of impacts and cumulative energy dissipation reached their maximum for all three energy levels. However, both the number of impacts and the cumulative energy dissipation decreased as the temperature increased or decreased. Interestingly, under 700 J impacts, the cumulative energy dissipation after the second impact at 200°C and − 196°C exceeded that of 100°C and − 78.5°C. This phenomenon can be attributed to the thermal decomposition of luffa fibers at 200°C and the crystallization of water at -196°C, which caused the LSRCC to exceed the termination condition of core concrete disintegration during the second impact at these temperatures, leading to more severe specimen failure compared to the other three temperatures (Fig. 4 e). High-speed imaging of the 300 ‍J impact at -196°C (Fig. 4 f) revealed a significant reduction in the constraint provided by the luffa fibers to the cement matrix, with the specimen displaying blocky failure in contrast to the high-speed images taken at 25°C (Fig. 3 c). This study demonstrates that, although the energy dissipation capacity of LSRCC specimens showed varying degrees of reduction in ultra-low-temperature environments, the overall failure morphology remained relatively intact, indicating the suitability of LSRCC as an impact-resistant material for ultra-low-temperature conditions. 2.4 Interface Characterization Following the completion of impact performance tests at both ambient, elevated, and ultra-low temperatures, this study proceeded with a mechanism-level analysis of the interface between the luffa sponge and the cement paste in LSRCC specimens using FIB combined with TEM, namely the FIB-TEM technique. FIB enables the precise cutting of sample material, preparing samples with a thickness on the order of tens of nanometers, making them suitable for TEM imaging. The samples prepared by FIB allow high-resolution imaging in the TEM, facilitating the observation of nanoscopic features such as crystal structures, defects, and dislocations. Figure 5 a shows the cross-sectional slices obtained via FIB sample preparation. From these, five regions were selected for further analysis: P1 and P2 located across the luffa sponge fiber-cement paste interface; C, located within the cement matrix; and L, within the fiber itself, as well as the broader Area M. The dark field (HADDF) and energy dispersive spectroscopy (EDS) mapping for Areas M (with Ca in yellow, Si in green, C in red, and K in orange) are shown in Fig. 5 b, with the interface marked in orange. Further magnification and EDS mapping of Area P2 is presented in Fig. 5 c, followed by a line scan along the indicated path, as shown in Fig. 5 d. In Fig. 5 e, region P1 is further divided into P1-1 (cement matrix), P1-2 (interface region containing both luffa fiber and cement), and P1-3 (within the luffa fiber). Enlargements of P1-1 and C, followed by Fast Fourier Transform (FFT) analysis, are shown in Fig. 5 f. Similarly, enlargements and FFT of P1-3 and L are presented in Fig. 5 g. The interface region P1-2 are magnified in Fig. 5 h, with the three lattice structures R1, R2, and R3 highlighted. The FFT and corresponding inverse FFT (IFFT) analyses of this interface region are also shown in Fig. 5 h, where the FFT of R1, R2, and R3 in FFT align along distinct rings, with the corresponding IFFT lattice fringes and spacings of 0.28 nm, 0.24 nm, and 0.17 nm. Based on the FIB-TEM analysis, it is evident that a distinct Interfacial Transition Zone (ITZ) exists between the luffa sponge fiber and the cement matrix, indicating that the connection between the two is not merely mechanical but exhibits certain synergistic effects. A possible explanation is that luffa sponge fibers, being hydrophilic, contain numerous hydroxyl groups (–OH) in their cellulose molecules, which can readily form hydrogen bonds with water molecules. This likely alters the water-to-cement ratio in the transition zone, creating a gradient in strength from the luffa sponge to the cement paste. This may explain the “1 + 1 > 2” effect observed under both static compressive and impact loads, where impact forces are efficiently transferred across the ITZ, leading to a more unified load-bearing performance in the LSRCC as opposed to localized failure. The failure modes observed in LSRCC specimens under compressive and impact loading further support this hypothesis. Building on the nanoscale experimental foundation, this study further conducted simulation analyses of the cement-cellulose interface using DFT. The primary objective was to model the distribution characteristics of water molecules at the cement-cellulose composite interface. All DFT calculations for periodic material systems were performed with the Vienna Ab initio simulation package (VASP) ( 32 ) using the projector-augmented wave (PAW) method ( 33 ). The exchange–correlation function was handled using the generalized gradient approximation (GGA) formulated by the Perdew-Burke-Ernzerhof (PBE) ( 34 ). The van der Waals (vdW) interactions are described with the DFT-D3 method in Grimme’s scheme ( 35 , 36 ). The interaction between the atomic core and electrons was described by the projector augmented wave method. The plane-wave basis energy cutoff was set to 500 eV ( 37 , 38 ). The Brillouin zone was sampled with a 3 × 3 × 1 grid centered at the gamma ( Γ ) point for geometry relaxation. All the slabbed models possessed a vacuum spacing of ≈ 15 Å sampled, ensuring negligible lateral interaction of adsorbates ( 39 ). The bottom layers about half of the structure were kept frozen at the lattice position ( 40 ). All structures were fully relaxed to optimize without any restriction until their total energies converged to < 1×10 −‍6 eV ( 41 , 42 ), and the average residual forces were < 0.02 eV/Å ( 43 , 44 ). To facilitate the DFT computational modeling of cement systems, we considered CaAl₂O₄ and CaSiO₃ as the primary approximate constituents of cement. Figures 5 i and 5 j illustrate the adsorption of water molecules on CaAl₂O₄ and CaSiO₃ surfaces, respectively, while Fig. 5 k depicts water molecule adsorption on cellulose. Analysis of the adsorption structures reveals that the water molecules adsorbed on cellulose form three hydrogen bonds with the cellulose matrix, indicating a robust interaction facilitated by the hydroxyl groups inherent to cellulose. The adsorption energies presented in Fig. 5 o further substantiate the superior affinity of cellulose for water molecules compared to CaAl₂O₄ and CaSiO₃. Specifically, the adsorption energy of water molecules on cellulose is calculated to be -2.51 eV, markedly higher than that on CaAl₂O₄ (-1.24 eV) and CaSiO₃ (-1.79 eV). This significant difference suggests that cellulose has a heightened propensity for water adsorption, likely due to its abundant hydrogen-bonding sites, which enhance its interaction with water molecules. Figures 5 l to 5 n display the reduced density gradient (RDG) scatter plots used for weak interaction analysis. The RDG isosurfaces are coloured within a sign( λ ₂) ρ range of -0.035 to 0.02 atomic units (a.u.), corresponding to weak interaction regions, utilizing the default blue-green-red colour scale. Notably, Fig. 5 n, representing cellulose with adsorbed water molecules, exhibits the most pronounced weak interactions among the samples studied. The increased intensity and distribution of the RDG isosurfaces in this figure indicate stronger van der Waals interactions and hydrogen bonding in the cellulose-water system, highlighting the significant role of weak interactions in the adsorption process on cellulose. Figure 5 p illustrates the electrostatic potential (ESP) surface of cellulose, revealing regions of both positive and negative potential, with a predominance of positive electrostatic potential. This positively charged surface is conducive to the adsorption of water molecules, as the electronegative oxygen atoms of water can interact favourably with these regions. The predominance of positive ESP regions on cellulose enhances its ability to attract and retain water molecules, further explaining the higher adsorption energy observed. 3. Conclusion The development of low-cost, high-performance impact-resistant materials has been a focus in materials science. This study presents luffa sponge reinforced cementitious composites (LSRCC), utilizing the natural topology-optimized fibers of luffa sponge to toughen cement paste despite its low intrinsic strength. Key findings are as follows: The uniaxial compressive tests reveal a strong synergistic effect between the cement matrix and the luffa sponge, resulting in improved stiffness, strength, and a transition from brittle to ductile failure modes. This confirms the potential of LSRCC as a high-performance impact-resistant material, with the luffa sponge effectively mitigating the inherent brittleness of the cement paste. The impact tests at ambient temperature demonstrated that LSRCC specimens exhibit excellent impact resistance, attributed to the reinforcing effect of the luffa sponge on the cement paste. Even under repeated impact loads, the specimens maintained structural integrity, transitioning from brittle to ductile failure modes and showcasing significant energy dissipation capabilities. The progressive damage evolution observed during repeated impacts revealed that the luffa sponge's spatially entangled fibers effectively mitigate the brittle nature of the cement paste. The increase in energy dissipation per impact, along with the broadening of the plateau stage in force-displacement curves, highlights the suitability of LSRCC for applications involving multiple impact loads. The impact tests across various temperatures demonstrated that LSRCC exhibits excellent adaptability to extreme thermal conditions, maintaining overall structural integrity despite reduced cumulative energy dissipation at high and ultra-low temperatures. At 200°C and − 196°C, the thermal decomposition of luffa fibers and water crystallization, respectively, led to higher energy dissipation during repeated impacts. These results confirm that the luffa sponge’s reinforcing effect effectively mitigates brittle failure, making LSRCC a reliable and impact-resistant material for extreme environments. The FIB-TEM analysis revealed the existence of a distinct Interfacial Transition Zone (ITZ) between the luffa sponge fibers and the cement matrix, characterized by a gradient in water-to-cement ratio. This suggests that the connection between the two is not merely mechanical but exhibits synergistic effects due to the hydrogen bonding facilitated by the hydrophilic cellulose in the luffa sponge. This ITZ enhances the load transfer across the interface, contributing to the observed “1 + 1 > 2” effect under both compressive and impact loads, thereby improving the overall structural integrity and impact resistance of LSRCC. The DFT simulations further confirmed that cellulose exhibits a significantly higher affinity for water molecules compared to the primary cement constituents CaAl₂O₄ and CaSiO₃, due to abundant hydrogen-bonding sites. This strong interaction enhances the ITZ's performance by creating a gradual strength transition, facilitating efficient load transfer and energy dissipation in LSRCC. 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Supplementary Files SupportingInformation.docx Supporting Information VideoS1.Quasistaticcompression.mp4 LSRCC specimen under quasi-static compression VideoS2.300Jimpactambient.mp4 LSRCC specimen under 300 J repeated impacts with ambient condition VideoS3.700Jimpactambient.mp4 LSRCC specimen under 700 J repeated impacts with ambient condition VideoS4.300Jimpact196deg.mp4 LSRCC specimen under 300 J repeated impacts at -196℃ VideoS5.700Jimpact196deg.mp4 LSRCC specimen under 700 J repeated impacts at -196℃ VideoS6.700Jimpact200deg.mp4 LSRCC specimen under 700 J repeated impacts at 200℃ Cite Share Download PDF Status: Published Journal Publication published 17 Nov, 2025 Read the published version in Communications Materials → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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09:25:35","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6367914/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6367914/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s43246-025-00985-y","type":"published","date":"2025-11-17T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82464446,"identity":"3ac1de5d-e05d-46ad-9dd9-08c9e69f7649","added_by":"auto","created_at":"2025-05-11 15:49:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":320048,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMorphology and mechanical characteristics of luffa sponge.\u003c/strong\u003e \u003cstrong\u003ea)\u003c/strong\u003eSchematic illustration of the luffa sponge and energy-absorbing structural units it has. \u003cstrong\u003eb)\u003c/strong\u003e Detailed structures of the outer layer, inner layer, and core region of the luffa sponge. \u003cstrong\u003ec)\u003c/strong\u003e Specific strength with respect to the specific modulus of natural materials.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/848263dca32a3738dc10bdb4.png"},{"id":82464448,"identity":"f5de5ad6-f1d5-48f7-bf37-cb40c1b799b9","added_by":"auto","created_at":"2025-05-11 15:49:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1058057,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacterization and mechanical performance of cement, luffa sponge, and LSRCC.\u003c/strong\u003e \u003cstrong\u003ea)\u003c/strong\u003e Load-deformation behavior of cement past under quasi-static compression. \u003cstrong\u003eb)\u003c/strong\u003e Particle size distribution of cement powder. \u003cstrong\u003ec, d)\u003c/strong\u003eX-ray diffraction (XRD) of raw cement before and after hydration. \u003cstrong\u003ee)\u003c/strong\u003eLoad-deformation behavior of luffa sponge under quasi-static compression. \u003cstrong\u003ef)\u003c/strong\u003eDeformation characteristics of luffa sponge under quasi-static compression. The longitudinal straight dashed lines buckled after compression, indicating significant folding of the luffa sponge. A scanning electron microscope (SEM) image exhibited the multi-tubular microstructure of the luffa sponge fiber. \u003cstrong\u003eg)\u003c/strong\u003ePreparation of LSRCC specimens. \u003cstrong\u003eh)\u003c/strong\u003e Load-deformation behavior of LSRCC under quasi-static compression. \u003cstrong\u003ei)\u003c/strong\u003e Damage and deformation of LSRCC at four typical stages, i.e., elastic (Ⅰ), cover cement spalling (Ⅱ), significant compression and damage (Ⅲ), and densely compressed (Ⅳ), corresponding to (\u003cstrong\u003eh\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/368d2797d8242bca11327203.png"},{"id":82464457,"identity":"dd34e8d2-de6a-4213-a15b-ac68eacecf1b","added_by":"auto","created_at":"2025-05-11 15:49:02","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1309854,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eImpact resistance properties of LSRCC at ambient temperature.\u003c/strong\u003e \u003cstrong\u003ea, b)\u003c/strong\u003eSetup of drop-weight impact test. \u003cstrong\u003ec)\u003c/strong\u003e High-speed photographs showing the damage processes of LSRCC subjected to repeated drop-weight impacts with the input energy of 300 J. \u003cstrong\u003ed)\u003c/strong\u003e Initial and residual states of LSRCC after repeated impacts. \u003cstrong\u003ee)\u003c/strong\u003e Force-displacement curves and energy absorption of LSRCC under repeated impacts.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/ca4dbf5b254939a371785d94.png"},{"id":82464463,"identity":"a0f38245-85b3-4856-b59a-8f3905aec52e","added_by":"auto","created_at":"2025-05-11 15:49:02","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1180472,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of environmental temperature on the impact resistance of LSRCC.\u003c/strong\u003e \u003cstrong\u003ea)\u003c/strong\u003e Peak force and energy dissipation of all LSRCC specimens at various temperature conditions. \u003cstrong\u003eb, c)\u003c/strong\u003e Peak force and energy dissipation of LSRCC specimens under the first impact. \u003cstrong\u003ed)\u003c/strong\u003e The cumulative energy dissipation of the LSRCC specimens subjected to repeated impacts at different temperatures. \u003cstrong\u003ee)\u003c/strong\u003eSide panorama view of the damage of the LSRCC specimens under the first impact at various temperatures with input energy of 300 J. \u003cstrong\u003ef)\u003c/strong\u003e High-speed photographs show the damage evolution of LSRCC subjected to repeated impacts with the temperature at -196 °C and input energy of 300 J.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/3895e57a192f8d0a088b9f34.png"},{"id":82464455,"identity":"c54ea589-b199-45bf-a9f9-8ce0da9c55dc","added_by":"auto","created_at":"2025-05-11 15:49:02","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1702480,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eNano-scale characterization of the ITZ.\u003c/strong\u003e \u003cstrong\u003ea)\u003c/strong\u003e The overall morphology of the target area obtained through FIB. \u003cstrong\u003eb, c) \u003c/strong\u003eThe HAADF micrograph and main element mappings of Ca, Si, C, and K covering Areas M and P2, respectively. \u003cstrong\u003ed)\u003c/strong\u003e The linescan profile of the four elements along the blue dashed line indicated in Area P2. \u003cstrong\u003ee)\u003c/strong\u003eMagnified image of Area P1, indicating the ITZ between cement and luffa sponge. \u003cstrong\u003ef)\u003c/strong\u003e Comparison of the zoomed-in images and FFT between Areas P1-1 and C. \u003cstrong\u003eg)\u003c/strong\u003eComparison of the zoomed-in images and FFT between Areas P1-3 and L. \u003cstrong\u003eh)\u003c/strong\u003e Zoomed-in image of the Area P1-2, and the FFT and IFFT of the phases corresponding to R1, R2, and R3, respectively. (\u003cstrong\u003ei\u003c/strong\u003e) Water adsorbed on CaAl₂O₄; (\u003cstrong\u003ej\u003c/strong\u003e) on CaSiO₃; (\u003cstrong\u003ek\u003c/strong\u003e) on cellulose, where water forms three hydrogen bonds with the cellulose backbone. (\u003cstrong\u003el-n\u003c/strong\u003e) RDG scatter plots for (\u003cstrong\u003ei–k\u003c/strong\u003e), highlighting weak interactions in the sign(\u003cem\u003eλ\u003c/em\u003e₂)\u003cem\u003eρ\u003c/em\u003e range of -0.035 to 0.02 a.u.; cellulose (\u003cstrong\u003en\u003c/strong\u003e) exhibits the strongest weak interactions. (\u003cstrong\u003eo\u003c/strong\u003e) Adsorption energies: cellulose (-2.51 eV), CaAl₂O₄ (-1.24 eV), and CaSiO₃ (-1.79 eV), indicating cellulose's higher affinity for water. (\u003cstrong\u003ep\u003c/strong\u003e) Electrostatic potential surface of cellulose, showing predominantly positive potential, which facilitates water molecule adsorption.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/d6933297e63299473485fcdb.png"},{"id":96153794,"identity":"f10068c3-d1d4-4bd2-bf4e-c845396f27f0","added_by":"auto","created_at":"2025-11-18 08:06:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6264088,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/2cb1249d-b674-4502-a6c8-636c61ad90f5.pdf"},{"id":82464450,"identity":"f232165f-126b-471d-9a2c-3ab8de0387aa","added_by":"auto","created_at":"2025-05-11 15:49:01","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3147071,"visible":true,"origin":"","legend":"Supporting Information","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/9f48d6e08ccea5000da7f8d0.docx"},{"id":82465051,"identity":"f3cfbf54-9c35-4741-8695-43dd371d59e2","added_by":"auto","created_at":"2025-05-11 16:05:02","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":37628098,"visible":true,"origin":"","legend":"LSRCC specimen under quasi-static compression","description":"","filename":"VideoS1.Quasistaticcompression.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/468f17aebbb26dc1421ef966.mp4"},{"id":82464462,"identity":"c6768c90-0ac1-4e8a-a8dd-294b4649164e","added_by":"auto","created_at":"2025-05-11 15:49:02","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":39858077,"visible":true,"origin":"","legend":"LSRCC specimen under 300 J repeated impacts with ambient condition","description":"","filename":"VideoS2.300Jimpactambient.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/3746af334f96701ed420ee1a.mp4"},{"id":82464466,"identity":"09680752-84a2-4bd9-a35c-a07b4719e905","added_by":"auto","created_at":"2025-05-11 15:49:02","extension":"mp4","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":13233599,"visible":true,"origin":"","legend":"LSRCC specimen under 700 J repeated impacts with ambient condition","description":"","filename":"VideoS3.700Jimpactambient.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/798cac7c1e2c175ec7b6adb2.mp4"},{"id":82464453,"identity":"eb980ca5-e10a-4e43-9a60-c523f5a1a562","added_by":"auto","created_at":"2025-05-11 15:49:02","extension":"mp4","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":13684884,"visible":true,"origin":"","legend":"LSRCC specimen under 300 J repeated impacts at -196\u0026#x2103;","description":"","filename":"VideoS4.300Jimpact196deg.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/93bd56ae3d9b1c2c26bca9af.mp4"},{"id":82464934,"identity":"ac15ad50-2e03-4b6b-b879-38758a96412d","added_by":"auto","created_at":"2025-05-11 15:57:02","extension":"mp4","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":8577148,"visible":true,"origin":"","legend":"\u003cp\u003eLSRCC specimen under 700 J repeated impacts at -196℃\u003c/p\u003e","description":"","filename":"VideoS5.700Jimpact196deg.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/2def9d524e69127620bbc9c3.mp4"},{"id":82464459,"identity":"a0ea1de8-b67d-4c31-b3ae-8e571e17d53b","added_by":"auto","created_at":"2025-05-11 15:49:02","extension":"mp4","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":8173534,"visible":true,"origin":"","legend":"\u003cp\u003eLSRCC specimen under 700 J repeated impacts at 200℃\u003c/p\u003e","description":"","filename":"VideoS6.700Jimpact200deg.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6367914/v1/15b3b3699384cae388d78452.mp4"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Bio-Based Impact-Resistant Materials: Luffa Sponge as a Sustainable Solution","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eImpact-resistant materials are crucial for applications where materials must absorb and dissipate energy effectively without significant deforming or failing under sudden impacts (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). These materials, such as metals (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e), rubbers (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e), ceramics (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e), and polymers (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e), are selected based on specific application needs. Impact-resistant cementitious composite materials have received increased interest due to their advantages (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). Notably, cementitious composites offer superior durability and longevity compared to metals and rubbers, making them ideal for infrastructure projects that demand low maintenance over long periods. Furthermore, when compared to advanced polymers and ceramics, cementitious composites are more economically viable due to their wide availability and lower cost of cement. For context, the global consumption of cement in 2023 was 4.2\u0026nbsp;billion tons, exceeding the production volumes of many staple crops, such as wheat (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). This vast scale of production underlines the accessibility and cost-effectiveness of cement as a raw material. Given these benefits, impact-resistant cementitious composites are extensively used in protective structures, especially in various strategically important infrastructures. For example, they are employed in the construction of nuclear power plants, particularly in containment structures designed to withstand extreme events (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Additionally, these materials are increasingly utilized in water treatment plants (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e), sewer systems (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e), and other facilities requiring durable materials capable of withstanding harsh, corrosive environments.\u003c/p\u003e \u003cp\u003eDespite the inherent quasi-brittle nature of cement, which exhibits brittle fractures under tensile and shear stresses, advancements in material science have led to significant improvements in its impact resistance. This is primarily achieved through the even dispersion of various fibers in a matrix, such as steel fiber, polyvinyl alcohol, and polypropylene fibers, enhancing the toughness, strength, and ductility of cementitious composites (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). These innovations have paved the way for the development of fiber-reinforced cementitious composites, such as Engineered Cementitious Composites (ECC) with ultra-high ductility and Ultra-High Performance Concrete (UHPC) noted for its exceptional strength (\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). Fibers enhance the impact resistance of cementitious composite by creating a fiber bridging effect that distributes stress across the matrix (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). However, often these fibers act independently (as they are distributed evenly in the matrix) without forming a unified network, and thus limit the potential for comprehensive impact resistance improvement (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). Moreover, traditional fiber-reinforced cementitious composites also exhibit cold brittleness, which is similar to metals and ceramics. As the temperature decreases, their toughness and energy dissipation capacity gradually decline, making them unsuitable for applications in extremely low-temperature environments (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). Recent research efforts including 3D-printing technology to manufacturing cement-based composites, were made aiming to overcome these limitations by forming integrated fiber networks to improve structural integrity and impact resistance (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). However, the implementation of 3D printing technology in this field still faces challenges related to precision, cost, and equipment capabilities, hindering its widespread application.\u003c/p\u003e \u003cp\u003eBuilding upon the technological advancements in cementitious composites, nature itself provides inspiration for impact-resistant materials through the example of the dried fibrous core of the loofah, a plant from the gourd family. The loofah\u0026rsquo;s fibrous structure is naturally equipped for impact resistance due to its three-dimensional, interlaced fiber network (\u003cem\u003e222\u003c/em\u003e, \u003cem\u003e233\u003c/em\u003e). This arrangement not only enhances the mechanical integrity and shock absorption capabilities but also aligns with the fundamental characteristics required for impact-resistant materials. Such bio-inspired designs highlight potential avenues for developing advanced materials that mimic these natural structures, offering improved performance and sustainability. Shen et al. (\u003cem\u003e244\u003c/em\u003e, \u003cem\u003e255\u003c/em\u003e) investigated the basic mechanical properties of luffa sponge and concluded that the luffa sponge was ideal for energy absorption applications as an ultra-light cellular material. The structure of the luffa sponge, characterized by a significant contact area due to its spatially chaotic fiber arrangement, has found successful applications in energy and environmental sectors in recent years (\u003cem\u003e266\u003c/em\u003e, \u003cem\u003e277\u003c/em\u003e). The morphology and mechanical characteristics of the luffa sponge, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, reveal various three-dimensional energy-absorbing structural units, e.g., tubular units, fibrous units, and cellular units (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). More importantly, the core area of the luffa sponge, which contains coarser fibers, provides a complete support system for the fibers in the outer wall region, thereby enhancing the overall structural integrity under axial load (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). Given these characteristics, the impact performance of the luffa sponge stands out within the realm of natural plants, making it an ideal, naturally topology-optimized green energy-absorbing material (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003eThis paper aims to systematically investigate bioinspired impact-resistant cementitious composite materials based on luffa sponge. Unlike the independent toughening mechanism of conventional short-cut fibers in cementitious composites, it is expected that the spatial network structure of luffa sponge fibers can form an integrated toughening system within the cementitious matrix. This study, for the first time, proposes the incorporation of the natural three-dimensional fiber system of luffa sponge into the cement matrix to enhance its toughness and evaluates the performance improvements through impact tests. Building on this, the study first investigates the impact resistance of luffa sponge-reinforced cementitious composites (LSRCC) under ambient conditions, confirming the enhancement in impact resistance provided by the luffa sponge within the cementitious paste. Subsequently, addressing the cold brittleness commonly observed in existing impact-resistant materials, the study is the first to explore the impact performance of LSRCC across a wide temperature range (from \u0026minus;\u0026thinsp;196\u0026deg;C to 200\u0026deg;C), validating its feasibility as an impact-resistant material for extreme environments. Moreover, utilizing a combination of Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM), the interface transition zone between the luffa sponge and the cementitious paste is characterized at the nanoscale, providing insights into the morphological and physicochemical features contributing to their synergistic behavior. Finally, based on Density Functional Theory (DFT), the interface between cement and the cellulose of luffa sponge was analyzed. The simulation modeled the distribution characteristics of water molecules at the cement-cellulose composite interface, verifying that the hydrogen bonding within the cellulose matrix contributes to the gradual variation in water-to-cement ratio across the interfacial region, thereby leading to a gradual transition in interfacial strength.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"2. Results and Discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Characterization of raw materials\u003c/h2\u003e \u003cp\u003eThe basic mechanical and physicochemical properties of cement and luffa sponge are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The cement used in this study is ordinary Portland cement (42.5R), with a fixed water-to-cement ratio of 0.3. The luffa sponge is derived from the vascular bundles of the mature fruit of the annual herbaceous plant Luffa (from the Cucurbitaceae family), commonly used as cleaning tools or seat cushions. The mechanical and physicochemical characteristics of cement are illustrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea through \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed. Under uniaxial compressive loading, the cement specimens exhibit typical brittle failure, which is why cement or concrete alone is generally unsuitable as impact-resistant materials. The uniaxial compressive behavior of the luffa sponge, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee, demonstrates notable force plateau and secondary stiffening characteristics. However, its compressive load capacity remains below 1 kN due to the abundant voids within the fiber bundles of the luffa sponge, exhibiting significant deformation with a normal strain exceeding 0.6 (see Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef). The microscopic porosity of the luffa sponge, shown in the right side of Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef, further indicates that it is not suitable for bearing loads independently.\u003c/p\u003e \u003cp\u003eThis study explores the combination of cement paste and luffa sponge, utilizing the luffa sponge to enhance the toughness of the cement paste. The production process of LSRCC is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg. First, cement is mixed with water to form a paste, after which the luffa sponge is fully immersed in the cement paste. The composite is then cured for 28 days under standard curing conditions (temperature 20\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C and humidity not less than 95%). Upon completion of the preparation and curing process, uniaxial compressive tests were conducted on the LSRCC specimens, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eh. The test results revealed a significant enhancement in both stiffness and strength in the LSRCC specimens, with peak force reaching 320 kN, exceeding the simple linear addition of the compressive strengths of cement and luffa sponge alone. This confirms the outstanding synergistic effect of cement matrix and luffa sponge in LSRCC. The failure process under axial compression is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ei, where the fiber toughening effect of the luffa sponge significantly improved the brittle nature of the cement paste, resulting in a clear ductile failure mode.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Preparation and Characterization\u003c/h2\u003e \u003cp\u003eFollowing the completion of the axial compressive mechanical performance tests on LSRCC, the impact resistance under ambient temperature was investigated. The CEAST-9250 drop-weight impact tester (Instron Co., Ltd, United States) was employed for this purpose, equipped with a high-speed camera Nova S9 made by Photron (resolution of 1024\u0026times;1024 pixels, frame rate of 9000 frames per second) to capture the failure process of the specimens, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea. In this study, the drop weight mass was set at 10.8 kg. Sensors embedded in the drop hammer automatically recorded data during the impact process, including parameters such as force, displacement, and energy. By varying the drop height, different input energies were achieved, specifically 300 J, 500 J, and 700 J, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb. In addition to varying the input energy, the study also examined the effects of multiple impacts on the cumulative damage evolution of LSRCC. This involved repeated impacts at a constant height, until the specimen was completely damaged, to simulate repeating impact loads that might be induced by mechanical transmission systems on the composite materials. When the impact energy was set to 300 J (drop height of 2820 mm), the failure process of the LSRCC specimen under repeated impacts was captured by the high-speed camera, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec.\u003c/p\u003e \u003cp\u003eThe images illustrate the failure characteristics of the specimen at the 1st, 5th, and 9th impacts. From these snapshots, it is evident that although the outer cement paste \u0026ldquo;protective layer\u0026rdquo; exhibited early delamination, the core luffa sponge and the encased cement paste maintained perfect synergy. Even after the 9th impact, the overall integrity of the specimen was preserved, demonstrating significant impact ductility. This result correlates well with the axial compressive test findings shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eh and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ei. The progressive failure modes of the LSRCC specimens after the 1st to 9th impact loads are depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed, clearly illustrating the damage evolution process. Despite noticeable outer layer delamination and crushing, the luffa sponge and cement paste continued to work in unison, confirming the effectiveness of the luffa sponge\u0026rsquo;s spatially entangled fibers in reinforcing the cement paste.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee presents the force-displacement curves and energy dissipation of the LSRCC specimens under different impact energies and impact counts. Overall, with increasing input impact energy, the peak force and absorbed energy of the LSRCC specimens showed an uprising trend. For a fixed input impact energy, the increase in the number of impacts caused a gradual reduction in peak force, yet the energy dissipation per impact increased progressively. Observing the force-displacement curves, it is apparent that with the increasing number of impacts, the \u0026ldquo;plateau stage\u0026rdquo; of the curve became wider. It is inferred that the luffa sponge fibers experience more pronounced delamination and fracture under repeated impact loads, and this \u0026ldquo;plateau stage\u0026rdquo; corresponds to the fiber delamination process within the cement paste. Naturally, the delamination and debonding of the fibers contribute to energy dissipation. The impact tests conducted at ambient temperature demonstrated that, thanks to the reinforcing effect of the luffa sponge on the cement paste, the LSRCC specimens exhibited excellent impact resistance. Notably, under repeated impact loads, there was a remarkable increase in the energy dissipation per impact, indicating that LSRCC specimens are highly suitable for applications involving multiple impact loads.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Environmental Temperature Effects\u003c/h2\u003e \u003cp\u003eFollowing the investigation of the impact resistance of LSRCC specimens under ambient temperature conditions, further research was conducted to examine the effect of environmental temperature on their impact resistance. During service, impact-resistant materials inevitably experience temperature fluctuations, and conventional materials often exhibit significant \u0026ldquo;temperature sensitivity\u0026rdquo; (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e). For both cementitious and metallic materials, it is generally observed that as the temperature decreases, strength and stiffness increase, while ductility significantly decreases (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). In this study, a drop-weight impact tester equipped with an environmental temperature chamber (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea) was used to perform in-situ high and low-temperature impact tests. For the high-temperature tests, the chamber was set to 100\u0026deg;C and 200\u0026deg;C, and the specimens were placed inside the heating chamber. Once the chamber reached the target temperature, it was maintained for 2 hours before the specimens were removed for impact testing. After each impact, the specimen was returned to the chamber and reheated to the set temperature before the next impact. For the low-temperature tests, the specimens were placed in a dry ice container, ensuring the dry ice fully covered the specimens with a layer of at least 5 cm on both the top and bottom. When the temperature, as measured by the environmental thermometer, reached \u0026minus;\u0026thinsp;78.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u0026deg;C, the specimens were kept in the container for 5 hours before undergoing impact testing. After each impact, the specimens were returned to the container to cool down to -78.5\u0026deg;C, and immediately after cooling, another impact was conducted. Furthermore, for ultra-low-temperature tests, the specimens were immersed in liquid nitrogen. When the environmental thermometer indicated a temperature of -196\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u0026deg;C, the specimens were held for 2 hours before being subjected to impact testing. Similar to the previous procedure, the specimens were re-cooled after each impact before the next round of testing. Throughout these tests, high-speed imaging and the sensors embedded in the drop-weight hammer were used to record the impact process. Impact tests were conducted at -196\u0026deg;C, -78.5\u0026deg;C, 25\u0026deg;C, 100\u0026deg;C, and 200\u0026deg;C, with repeated impacts at energy levels of 300 J, 500 J, and 700 J (the input energy at the moment the hammerhead contacted with the specimen).\u003c/p\u003e \u003cp\u003eAll the energy dissipated by the specimen during each impact and the corresponding peak force recorded by the drop hammer are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, with additional data extracted from this figure for comparison. As shown, the number of repeated impacts decreases as the temperature increases or decreases for all three energy levels, with the most pronounced reduction observed at 300 J, where the impact count dropped from 9 at 25\u0026deg;C to 3 at both 200\u0026deg;C and \u0026minus;\u0026thinsp;196\u0026deg;C. In terms of peak force during the first impact, no significant temperature sensitivity was observed for all three energy levels (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). Similarly, when the energy dissipated in the first impact was normalized by the input energy of the hammer, the energy dissipation also showed no significant temperature sensitivity across the three energy levels (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). Considering the disintegration of the core matrix as the termination condition, the cumulative energy dissipation of the specimens subjected to repeated impacts at different temperatures and energy levels is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed. At 25\u0026deg;C, the number of impacts and cumulative energy dissipation reached their maximum for all three energy levels. However, both the number of impacts and the cumulative energy dissipation decreased as the temperature increased or decreased. Interestingly, under 700 J impacts, the cumulative energy dissipation after the second impact at 200\u0026deg;C and \u0026minus;\u0026thinsp;196\u0026deg;C exceeded that of 100\u0026deg;C and \u0026minus;\u0026thinsp;78.5\u0026deg;C. This phenomenon can be attributed to the thermal decomposition of luffa fibers at 200\u0026deg;C and the crystallization of water at -196\u0026deg;C, which caused the LSRCC to exceed the termination condition of core concrete disintegration during the second impact at these temperatures, leading to more severe specimen failure compared to the other three temperatures (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee). High-speed imaging of the 300 \u0026zwj;J impact at -196\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef) revealed a significant reduction in the constraint provided by the luffa fibers to the cement matrix, with the specimen displaying blocky failure in contrast to the high-speed images taken at 25\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). This study demonstrates that, although the energy dissipation capacity of LSRCC specimens showed varying degrees of reduction in ultra-low-temperature environments, the overall failure morphology remained relatively intact, indicating the suitability of LSRCC as an impact-resistant material for ultra-low-temperature conditions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Interface Characterization\u003c/h2\u003e \u003cp\u003eFollowing the completion of impact performance tests at both ambient, elevated, and ultra-low temperatures, this study proceeded with a mechanism-level analysis of the interface between the luffa sponge and the cement paste in LSRCC specimens using FIB combined with TEM, namely the FIB-TEM technique. FIB enables the precise cutting of sample material, preparing samples with a thickness on the order of tens of nanometers, making them suitable for TEM imaging. The samples prepared by FIB allow high-resolution imaging in the TEM, facilitating the observation of nanoscopic features such as crystal structures, defects, and dislocations. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows the cross-sectional slices obtained via FIB sample preparation. From these, five regions were selected for further analysis: P1 and P2 located across the luffa sponge fiber-cement paste interface; C, located within the cement matrix; and L, within the fiber itself, as well as the broader Area M. The dark field (HADDF) and energy dispersive spectroscopy (EDS) mapping for Areas M (with Ca in yellow, Si in green, C in red, and K in orange) are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, with the interface marked in orange. Further magnification and EDS mapping of Area P2 is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, followed by a line scan along the indicated path, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee, region P1 is further divided into P1-1 (cement matrix), P1-2 (interface region containing both luffa fiber and cement), and P1-3 (within the luffa fiber). Enlargements of P1-1 and C, followed by Fast Fourier Transform (FFT) analysis, are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef. Similarly, enlargements and FFT of P1-3 and L are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg. The interface region P1-2 are magnified in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eh, with the three lattice structures R1, R2, and R3 highlighted. The FFT and corresponding inverse FFT (IFFT) analyses of this interface region are also shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eh, where the FFT of R1, R2, and R3 in FFT align along distinct rings, with the corresponding IFFT lattice fringes and spacings of 0.28 nm, 0.24 nm, and 0.17 nm.\u003c/p\u003e \u003cp\u003eBased on the FIB-TEM analysis, it is evident that a distinct Interfacial Transition Zone (ITZ) exists between the luffa sponge fiber and the cement matrix, indicating that the connection between the two is not merely mechanical but exhibits certain synergistic effects. A possible explanation is that luffa sponge fibers, being hydrophilic, contain numerous hydroxyl groups (\u0026ndash;OH) in their cellulose molecules, which can readily form hydrogen bonds with water molecules. This likely alters the water-to-cement ratio in the transition zone, creating a gradient in strength from the luffa sponge to the cement paste. This may explain the \u0026ldquo;1\u0026thinsp;+\u0026thinsp;1\u0026thinsp;\u0026gt;\u0026thinsp;2\u0026rdquo; effect observed under both static compressive and impact loads, where impact forces are efficiently transferred across the ITZ, leading to a more unified load-bearing performance in the LSRCC as opposed to localized failure. The failure modes observed in LSRCC specimens under compressive and impact loading further support this hypothesis.\u003c/p\u003e \u003cp\u003eBuilding on the nanoscale experimental foundation, this study further conducted simulation analyses of the cement-cellulose interface using DFT. The primary objective was to model the distribution characteristics of water molecules at the cement-cellulose composite interface. All DFT calculations for periodic material systems were performed with the Vienna Ab initio simulation package (VASP) (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e) using the projector-augmented wave (PAW) method (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). The exchange\u0026ndash;correlation function was handled using the generalized gradient approximation (GGA) formulated by the Perdew-Burke-Ernzerhof (PBE) (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). The van der Waals (vdW) interactions are described with the DFT-D3 method in Grimme\u0026rsquo;s scheme (\u003cem\u003e35\u003c/em\u003e, \u003cem\u003e36\u003c/em\u003e). The interaction between the atomic core and electrons was described by the projector augmented wave method. The plane-wave basis energy cutoff was set to 500 eV (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). The Brillouin zone was sampled with a 3 \u0026times; 3 \u0026times; 1 grid centered at the gamma (\u003cem\u003eΓ\u003c/em\u003e) point for geometry relaxation. All the slabbed models possessed a vacuum spacing of \u0026asymp;\u0026thinsp;15 \u0026Aring; sampled, ensuring negligible lateral interaction of adsorbates (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). The bottom layers about half of the structure were kept frozen at the lattice position (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). All structures were fully relaxed to optimize without any restriction until their total energies converged to \u0026lt;\u0026thinsp;1\u0026times;10\u003csup\u003e\u0026minus;\u0026zwj;6\u003c/sup\u003e eV (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e), and the average residual forces were \u0026lt;\u0026thinsp;0.02 eV/\u0026Aring; (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo facilitate the DFT computational modeling of cement systems, we considered CaAl₂O₄ and CaSiO₃ as the primary approximate constituents of cement. Figures\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ei and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ej illustrate the adsorption of water molecules on CaAl₂O₄ and CaSiO₃ surfaces, respectively, while Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ek depicts water molecule adsorption on cellulose. Analysis of the adsorption structures reveals that the water molecules adsorbed on cellulose form three hydrogen bonds with the cellulose matrix, indicating a robust interaction facilitated by the hydroxyl groups inherent to cellulose. The adsorption energies presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eo further substantiate the superior affinity of cellulose for water molecules compared to CaAl₂O₄ and CaSiO₃. Specifically, the adsorption energy of water molecules on cellulose is calculated to be -2.51 eV, markedly higher than that on CaAl₂O₄ (-1.24 eV) and CaSiO₃ (-1.79 eV). This significant difference suggests that cellulose has a heightened propensity for water adsorption, likely due to its abundant hydrogen-bonding sites, which enhance its interaction with water molecules. Figures\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003el to \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003en display the reduced density gradient (RDG) scatter plots used for weak interaction analysis. The RDG isosurfaces are coloured within a sign(\u003cem\u003eλ\u003c/em\u003e₂)\u003cem\u003eρ\u003c/em\u003e range of -0.035 to 0.02 atomic units (a.u.), corresponding to weak interaction regions, utilizing the default blue-green-red colour scale. Notably, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003en, representing cellulose with adsorbed water molecules, exhibits the most pronounced weak interactions among the samples studied. The increased intensity and distribution of the RDG isosurfaces in this figure indicate stronger van der Waals interactions and hydrogen bonding in the cellulose-water system, highlighting the significant role of weak interactions in the adsorption process on cellulose. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ep illustrates the electrostatic potential (ESP) surface of cellulose, revealing regions of both positive and negative potential, with a predominance of positive electrostatic potential. This positively charged surface is conducive to the adsorption of water molecules, as the electronegative oxygen atoms of water can interact favourably with these regions. The predominance of positive ESP regions on cellulose enhances its ability to attract and retain water molecules, further explaining the higher adsorption energy observed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Conclusion","content":"\u003cp\u003eThe development of low-cost, high-performance impact-resistant materials has been a focus in materials science. This study presents luffa sponge reinforced cementitious composites (LSRCC), utilizing the natural topology-optimized fibers of luffa sponge to toughen cement paste despite its low intrinsic strength. Key findings are as follows:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe uniaxial compressive tests reveal a strong synergistic effect between the cement matrix and the luffa sponge, resulting in improved stiffness, strength, and a transition from brittle to ductile failure modes. This confirms the potential of LSRCC as a high-performance impact-resistant material, with the luffa sponge effectively mitigating the inherent brittleness of the cement paste.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe impact tests at ambient temperature demonstrated that LSRCC specimens exhibit excellent impact resistance, attributed to the reinforcing effect of the luffa sponge on the cement paste. Even under repeated impact loads, the specimens maintained structural integrity, transitioning from brittle to ductile failure modes and showcasing significant energy dissipation capabilities.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe progressive damage evolution observed during repeated impacts revealed that the luffa sponge's spatially entangled fibers effectively mitigate the brittle nature of the cement paste. The increase in energy dissipation per impact, along with the broadening of the plateau stage in force-displacement curves, highlights the suitability of LSRCC for applications involving multiple impact loads.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe impact tests across various temperatures demonstrated that LSRCC exhibits excellent adaptability to extreme thermal conditions, maintaining overall structural integrity despite reduced cumulative energy dissipation at high and ultra-low temperatures. At 200\u0026deg;C and \u0026minus;\u0026thinsp;196\u0026deg;C, the thermal decomposition of luffa fibers and water crystallization, respectively, led to higher energy dissipation during repeated impacts. These results confirm that the luffa sponge\u0026rsquo;s reinforcing effect effectively mitigates brittle failure, making LSRCC a reliable and impact-resistant material for extreme environments.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe FIB-TEM analysis revealed the existence of a distinct Interfacial Transition Zone (ITZ) between the luffa sponge fibers and the cement matrix, characterized by a gradient in water-to-cement ratio. This suggests that the connection between the two is not merely mechanical but exhibits synergistic effects due to the hydrogen bonding facilitated by the hydrophilic cellulose in the luffa sponge. This ITZ enhances the load transfer across the interface, contributing to the observed \u0026ldquo;1\u0026thinsp;+\u0026thinsp;1\u0026thinsp;\u0026gt;\u0026thinsp;2\u0026rdquo; effect under both compressive and impact loads, thereby improving the overall structural integrity and impact resistance of LSRCC.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe DFT simulations further confirmed that cellulose exhibits a significantly higher affinity for water molecules compared to the primary cement constituents CaAl₂O₄ and CaSiO₃, due to abundant hydrogen-bonding sites. This strong interaction enhances the ITZ's performance by creating a gradual strength transition, facilitating efficient load transfer and energy dissipation in LSRCC. The pronounced van der Waals interactions and hydrogen bonding in the cellulose-water system further highlight the critical role of weak interactions in reinforcing the cement-cellulose interface.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThis work was funded by the Fundamental Research Funds for the Central Universities (No.2242022k30030 and No.2242022k30031). Thanks also to the Humboldt Foundation for the Humboldt Research Fellowship.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eR. P. Behera, H. Le Ferrand, Impact-resistant materials inspired by the mantis shrimp's dactyl club. Matter 4, 2831\u0026ndash;2849 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eT. Tetsui, Identifying low-cost, machinable, impact-resistant TiAl alloys suitable for last-stage turbine blades of jet engines. 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Nanoscale 15, 2756\u0026ndash;2766 (2023).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6367914/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6367914/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper develops low-cost, high-performance impact-resistant materials using natural luffa sponge as reinforcement for cementitious composites. It is the first to investigate the effect of temperature on the impact performance of luffa sponge-reinforced cementitious composites (LSRCC) across a wide range from \u0026minus;\u0026thinsp;196\u0026deg;C to 200\u0026deg;C. Addressing the brittleness of traditional materials at low temperatures, this study pioneers a sustainable, ultra-low-temperature impact-resistant material. Experimental results indicate a strong synergy between the luffa sponge and cement matrix, with the sponge\u0026rsquo;s networked fibers significantly enhancing structural integrity. Remarkably, LSRCC maintains cohesion under repeated impacts with minimal disintegration. It also exhibits low temperature sensitivity and excellent impact resistance in extreme environments. Interface properties between the luffa sponge and cement matrix were characterized using Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM), supported by Density Functional Theory (DFT) simulations. Results confirm a gradual Interfacial Transition Zone (ITZ) rather than a simple mechanical bond. Simulations reveal that hydrogen bonding within the cellulose matrix drives a gradual variation in the water-to-cement ratio across the interface, resulting in a progressive transition in interfacial strength. This transitional region enhances the load-bearing capacity of LSRCC, highlighting its superior synergistic behavior.\u003c/p\u003e","manuscriptTitle":"Bio-Based Impact-Resistant Materials: Luffa Sponge as a Sustainable Solution","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-11 15:48:56","doi":"10.21203/rs.3.rs-6367914/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"communications-materials","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"commsmat","sideBox":"Learn more about [Communications Materials](https://www.nature.com/commsmat/)","snPcode":"","submissionUrl":"","title":"Communications Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Communications Series","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"9b823dca-5315-46e2-b7d1-b8ab9de512e6","owner":[],"postedDate":"May 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":47767351,"name":"Physical sciences/Materials science/Structural materials/Composites"},{"id":47767352,"name":"Physical sciences/Engineering/Civil engineering"}],"tags":[],"updatedAt":"2025-11-18T08:06:32+00:00","versionOfRecord":{"articleIdentity":"rs-6367914","link":"https://doi.org/10.1038/s43246-025-00985-y","journal":{"identity":"communications-materials","isVorOnly":false,"title":"Communications Materials"},"publishedOn":"2025-11-17 05:00:00","publishedOnDateReadable":"November 17th, 2025"},"versionCreatedAt":"2025-05-11 15:48:56","video":"","vorDoi":"10.1038/s43246-025-00985-y","vorDoiUrl":"https://doi.org/10.1038/s43246-025-00985-y","workflowStages":[]},"version":"v1","identity":"rs-6367914","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6367914","identity":"rs-6367914","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}