This study presents an acoustic emission (AE)-based approach for analyzing damage mechanisms in woven lattice sandwich-ply laminated panels (SLPs). Six types of SLPs, varying in sandwich-ply number and core orientation, were prepared and tested under edgewise compression. The digital image correlation revealed distinct deformation patterns of SLPs, including compression-bending coupling, global buckling. AE characteristic parameters were extracted and reduced to three principal components via factor analysis. Fuzzy C-means (FCM) clustering was then applied to classify AE events, enabling identification of distinct damage modes. Three dominant damage mechanisms were revealed, including core shear failure, core fracture, and face fracture. The AE-based classifications were consistent with deformation patterns observed via digital image correlation method, including compression-bending coupling and global buckling, confirming the reliability of the approach. The proposed AE-FCM framework provides a technique for real-time monitoring and qualitative characterization of progressive damage in SLPs with multi-layered configuration.

Auxetic structures theoretically offer significant potential for regulating material damage evolution; however, the understanding of their synergistic mechanisms with cement matrices under multi-field coupling conditions remains limited. This study employs 3D printing technology to fabricate two-dimensional re-entrant honeycomb auxetic structures with three distinct angles using PA12, which are embedded as reinforcements in cementitious materials to construct novel cement-based wall structures. Uniaxial compression tests combined with digital image correlation (2D-DIC) and acoustic emission (AE) monitoring reveal that these novel cement-based wall structures not only retain the anomalous mechanical properties characteristic of cement composites but also exhibit compressive strength enhancements of 64.78%, 58.04%, and 47.70% compared to conventional walls, along with post-peak energy absorption capacities per unit volume increased by 99.5, 54.23, and 83.42 times relative to the control group. Strain field analysis demonstrates that the precisely controlled geometric topology of the novel wall structures effectively suppresses lateral expansion of the cement matrix and delays crack propagation. AE signal characteristics indicate that the novel wall structures facilitate a transition in damage evolution from brittle to ductile failure, promoting more orderly crack development. Furthermore, damage pattern classification based on factor analysis and fuzzy C-means clustering corroborates the restructuring effect of the novel cement-based wall structures on damage chronology. This research demonstrates that 3D-printed auxetic-reinforced cement-based wall structures exhibit exceptional compressive performance, energy absorption capacity, and damage regulation capabilities, offering innovative solutions for high-performance structural design in seismic-resistant construction and protective engineering.

3D printing technology offers a novel approach to mitigating the inherent brittleness of traditional cement-based materials. Current research primarily focuses on the optimization of lattice topological configurations and the enhancement of macroscopic mechanical properties. However, systematic studies remain insufficient regarding the internal meso-scale damage evolution, the deformation coordination behavior at the lattice-matrix interface under loading, and the regulatory laws of structural configurations on failure mechanisms in lattice-reinforced cementitious composites. To address this research gap, this study conducted uniaxial compression tests on 3Dprinted nylon lattice-reinforced cementitious composites featuring BCC and Warmuth topological configurations, utilizing in-situ X-ray computed tomography (CT). The lattice structure was extracted using a marker-controlled watershed segmentation algorithm, and voids and cracks were quantitatively distinguished based on the shape factor. Furthermore, an incremental global digital volume correlation (DVC) method was employed to characterize the evolutionary features of the internal 3D full-field strain. The results demonstrate that the lattice topological configuration significantly regulates the damage modes and evolution processes of the composites. The damage in BCC lattice specimens exhibits localized characteristics, with limited crack initiation in the early loading stages and directional propagation of main cracks along the lattice-matrix interfaces in the later stages. Conversely, the Warmuth negative Poisson's ratio lattice enters the stable microcrack propagation stage earlier, characterized by a diffuse multi-crack propagation pattern within the matrix, followed by extensive interfacial debonding and lattice buckling in the late loading stages.

In the northern areas of Pakistan, the fabric mostly used for wearing purposes is polyester (polyethylene terephthalate (PET). Due to its versatile quality, concrete is the most demanding construction material. In this study, durability & mechanical properties of polyester concrete (PC) are investigated by including raw polyester fibre (PF) with varying percentages (0,0; 0,5; 1,0; 1,5; and 2,0 %). Additionally, 1% sodium carbonate is used as a cement replacement. The results reveal that the addition of 1 % polyester (PET) fibre by weight produces 25,0 and 20,6 % increases in tensile and compressive strengths, respectively. The increased percentage of fibre also significantly reduces chloride permeability, indicating improved crack resistance in concrete. However, fibre additions of 1,5 or 2,0 % may result in reduced compressive strength and increased permeability. Therefore, 1 % polyester fibre is recommended for the application of concrete tension members and mortar in external walls. Moreover, this research focuses on the sustainable use of raw polyester as a constructive approach towards addressing environmental challenges associated with conserving resources, waste disposal, and mitigating environmental pollution.

Lightweight energy-absorbing structures are critical for aerospace and automotive crashworthiness, yet traditional auxetic honeycombs often suffer from global buckling and limited crushing stability. To address these limitations, this study proposes a bioinspired structural design featuring a functional member hierarchy inspired by the “trunk–bifurcation–constraint” load-transfer mechanism of the human shoulder girdle system (sternum–clavicle–scapula). Unlike conventional lattices, the proposed design integrates polyurethane (PU) foam to construct a series of lattice–foam hybrid composites that effectively mitigate localized instability and enhance energy dissipation. Four representative three-dimensional bioinspired honeycomb lattice structures (including baseline, high-energy-absorption, centrally-regulated, and high-stiffness variants) were fabricated using fused deposition modeling (FDM). In these architectures, the main struts mimic the load-bearing backbone, while the re-entrant inclined ribs induce a negative Poisson’s ratio (NPR) effect to facilitate material densification. Quasi-static compression tests were conducted to investigate the deformation modes and energy absorption characteristics. The results indicate that the in-situ foaming process discernibly improves the interfacial bonding and constrains the lateral deformation of the lattice struts. Specifically, the synergistic effect between the bioinspired topology and the foam core enhances the Specific Energy Absorption (SEA) and delays the onset of densification. This study demonstrates that the proposed bioinspired strategy offers a promising route for developing lightweight, high-performance crashworthiness components.

Concrete and mortar exhibit durability limitations in aggressive environments due to cracking, high permeability, and construction defects. Polymer-modified and self-healing cementitious materials have emerged as sustainable solutions; however, the synergistic use of polymer modifiers with chemical–biological healing agents remains underexplored.This study investigates self-healing polymer-modified mortar (SHPMM) incorporating styrene butadiene rubber (SBR) and ethylene vinyl acetate (EVA) as partial cement replacements at 0%,4%,8%,12% & 16%. A healing system consisting of 5% calcium lactate, 5% sodium silicate, 1% sodium carbonate. Also 1% effective microorganisms was added to all mixes. Workability, mechanical performance, durability, and microstructural characteristics were evaluated through slump, ultrasonic pulse velocity, strength tests, rapid chloride permeability, SEM, and EDX analyses.The results indicate that polymer addition significantly improves workability, strength, and durability. Slump values increased steadily with increasing polymer content. Optimum performance was observed at 4% and 8% polymer replacement, where permeability was markedly reduced. Compared to the control mix, compressive strength increased by 7–11%, split tensile strength by 12–17%, and flexural strength by 31–33%. RCPT values decreased substantially, with reductions of 32% and 45% for 4% and 8% SBR, and 22% and 58% for 4% and 8% EVA, respectively. Microstructural analysis confirmed improved matrix densification and crack-healing efficiency. EVA demonstrated superior performance compared to SBR, attributed to its powdered form and enhanced bonding characteristics.Overall, the combined application of polymer modifiers and healing agents effectively improves the mechanical performance, durability, and self-healing efficiency of cementitious composites, offering a viable solution for sustainable infrastructure in aggressive environments.

Acoustic emission (AE) was employed to characterize the mechanical behavior of repaired multi-layered woven lattice sandwich composite (MWLSC) in this paper. A patch repair strategy was adopted, in which damaged cores were reconstructed with polyurethane foam and fractured face sheets were restored using fiber fabric. Mechanical recovery was evaluated through mechanical testing, and AE monitoring was used to analyze damage evolution before and after repair. The repaired double-layered and triple-layered warp specimens recovered 123% and 104% of their original peak load, respectively, while the triple-layered weft specimen recovered 83%. Compared with pristine specimens, repaired MWLSC exhibited reduced cumulative AE counts and lower proportions of high-energy events. Continuous wavelet transform analysis revealed that the high-frequency components associated with interfacial delamination were significantly diminished after repair. These results indicate that repair modifies the dominant failure mechanism, shifting from delamination-dominated fracture toward core-related damage. The study demonstrates the effectiveness of AE techniques in capturing changes in damage evolution and mechanical response in repaired MWLSC.

This study investigates the width-dependent tensile behavior and damage mechanisms of ±45° carbon fiber–reinforced polymer (CFRP) laminates through an integrated Digital Image Correlation (DIC) and Acoustic Emission (AE) monitoring framework. Specimens of three widths (25 mm, 45 mm, and 100 mm) were subjected to quasi-static tensile loading while synchronously recording full-field strain evolution and internal damage events. DIC results reveal a clear transition in strain-field morphology with increasing width, from narrow banded shear localization to broader and more uniform “diamond-shaped” deformation patterns. AE monitoring captures corresponding changes in internal damage progression. After screening AE events above 40 dB and within the 100–600 kHz bandwidth, multi-parametric AE features were reduced using factor analysis/PCA, which revealed distinct clustering distributions associated with different specimen widths. Narrow specimens exhibited feature concentrations linked to matrix-dominated microcracking, medium-width specimens showed mixed matrix–interface interactions, and wide specimens exhibited high-energy signatures corresponding to fiber-dominated fracture. These dimensionality-reduction results directly demonstrate how specimen width regulates the underlying damage modes and AE response characteristics. Overall, the combined AE–DIC analysis provides a multi-scale understanding of deformation–damage coupling in ±45° CFRP laminates and offers quantitative evidence useful for structural design optimization and refinement of relevant ASTM/ISO shear testing standards.

To preserve the negative Poisson’s ratio characteristic of the re-entrant auxetic hexagonal structure while enhancing its mechanical properties, triangular folded ribs were incorporated into the re-entrant auxetic hexagonal structure (RAH), thereby establishing a novel triangular rib-enhanced re-entrant auxetic hexagonal structure (TRH). TRH specimens were prepared via additive manufacturing (AM) and subjected to quasi-static compression testing using a universal testing machine to investigate their mechanical properties. The results indicate that compared to RAH, the structure exhibited a second plateau in stress and demonstrated superior mechanical properties. For example, SEA increased by 75.5

The negative Poisson's ratio cylindrical structure, as a novel metamaterial, presents significant application potential, particularly in aerospace and civil engineering. This study designs and fabricates a new negative Poisson's ratio cylindrical structure, systematically investigating the effects of internal concave angle and wall thickness on the compressive performance and negative Poisson's ratio effect through experimental research and finite element analysis. The results indicate that decreasing the internal concave angle significantly enhances the structure's load-bearing capacity and energy absorption efficiency per unit mass. While increasing wall thickness improves total energy absorption, its effect on energy absorption per unit mass is relatively limited. Furthermore, the reduction in internal concave angle and the increase in wall thickness enhance compressive strength but diminish the negative Poisson's ratio effect. This research provides essential theoretical insights for the optimization of negative Poisson's ratio cylindrical structures in engineering applications.

Using polylactic acid (PLA), polyamide (PA) and glass fiber–reinforced polyamide (GF/PA) as raw materials, samples with different printing temperature and speed were prepared. PLA samples were prepared by fused deposition modeling, and PA and PA/GF samples were prepared by selective laser sintering. The fracture toughness of 3D printed engineering plastics was characterized by three-point bending test. The results show that the process parameters have little effect on the fracture toughness of the specimen. With the change of printing temperature or speed, the fracture toughness of the specimen decreases by 4.9%. The raw materials have great influence on the fracture toughness of the specimens. The fracture toughness of PLA increases by 27.95% compared with PA and 58.71% with GF/PA. The results show that the fracture toughness of PLA is the highest among the three materials. Finally, the fracture surface of the specimen was scanned by scanning electron microscope, and the fracture microstructure was analyzed to reveal the influence of process parameters and raw materials on the fracture toughness of 3D printed engineering plastics.

This study explores the low-cycle fatigue characteristics of three structural components fabricated from Ti2AlNb-based alloys utilizing Seeger’s fatigue life theory and an improved Lemaitre damage evolution model. The validity and accuracy of the simulations based on these theoretical methods are verified by experimental fatigue life tests conducted at high temperatures. Additionally, the potential of employing long short-term memory (LSTM), extreme learning machine (ELM), and partial least squares (PLS) algorithms to predict the high-temperature, low-cycle fatigue life of Ti2AlNb alloy components is examined. Comparative analyses of the training effectiveness and practical applicability of these machine learning approaches are conducted, demonstrating that ELM exhibits superior predictive capability. This investigation thus provides a practical and efficient predictive methodology for assessing the low-cycle fatigue life of structural components composed of Ti2AlNb-based alloys.

This paper explores the potential applications of 4D printing technology in the aerospace field, with a focus on the mechanical properties and reusability of honeycomb metamaterials with shape memory characteristics fabricated using shape memory polymers (SMPs). Currently, research on the reusability of SMP-based metamaterials is limited, particularly regarding the influence of cellular unit geometries on their recovery performance, which remains unclear. To address this gap, this study combines typical cellular units with positive, negative, and zero Poisson's ratio properties into various structures. Through quasi-static compression experiments, complemented by three-dimensional digital image correlation (DIC) technology and finite element analysis, the mechanical compression performance and deformation mechanisms of the three structures are compared in detail. The deformation patterns under compression are elucidated, and the influence of geometric shapes on deformation behavior and mechanical response is analyzed. Shape memory recovery experiments, including single-cycle and multi-cycle tests, are designed to evaluate the 4D smart recovery performance of the three structures in terms of key metrics such as recovery rate and restoring force. This study systematically characterizes the compressive mechanical properties and shape memory recovery characteristics of honeycomb structures with different Poisson's ratio combinations, providing significant guidance for the research and development of 4D-printed mechanical metamaterials. Highlights Metamaterial structures combining unit cells with different Poisson's ratios. DIC and FEM are used to assess the effects of unit cells on deformation and failure. ZAZ structure shows superior stiffness and energy absorption in compression. Evaluate the shape memory performance of SMP under loading conditions. ZAP structure exhibits more stable cyclic recovery behavior under loading.

In the field of structural engineering and impact protection, the development of lightweight and high-strength materials and structural forms has gained significant attention. Honeycomb structures, known for their exceptional specific strength, stiffness, and energy absorption capabilities, are widely used in various applications. However, most studies on the low-velocity impact performance of honeycomb structures have focused on configurations with a single type of cell element. Therefore, this study investigates the differences in mechanical properties by conducting low-velocity impact experiments on unit cells combined with different Poisson's ratio characteristics. It also explores the effect of lightweight polyurethane foam filling on the overall performance of the honeycomb structure, while analyzing the influence of punch geometry on the mechanical properties. The findings indicate that honeycomb structures with different cell element combinations exhibit varying mechanical responses under low-velocity impact, with the combination of elements having a zero Poisson's ratio demonstrating the best impact resistance. Furthermore, the polyurethane foam-filled honeycomb structure significantly improves energy absorption during impact, with the foam enhancing both the energy absorption capacity and cushioning performance. Additionally, the punch radius has an observable effect on the impact performance.

± 45° fiber-reinforced composites are widely used in aerospace, automotive, sports equipment, wind energy, and other fields due to their unique structural properties, offering excellent mechanical performance and reliability. This study investigates the effect of specimen width on the tensile properties and failure mechanisms of ± 45° fiber-reinforced composites. By combining digital image correlation (DIC) technology with finite element analysis (FEA), the commonalities and differences in full-field strain distribution, potential damage mechanisms, and crack propagation paths of specimens with different widths are systematically explored. A quantitative relationship between specimen width and load-carrying capacity is established, and the initial stiffness and ductility of the three width specimens are correlated. The results show that the load-carrying capacity of the 100 mm width specimens increases by approximately 353 and 133

Cellular structures often experience complex bending loads during practical applications. Therefore, thoroughly investigating their mechanical response under three-point bending conditions is essential for evaluating structural safety and reliability. This study investigates the bending performance of honeycomb structures composed of typical unit cells exhibiting positive, negative, and zero Poisson's ratios. By systematically combining these cells in pairs, quasi-static three-point bending tests were conducted to examine variations in failure modes, force-displacement behavior, and key mechanical properties across different configurations. In addition, foam-filling technology was integrated with 3D-printed honeycomb structures. Digital Image Correlation (DIC) was employed to analyze the effect of foam filling on the damage evolution process of the honeycomb structures, revealing the underlying strengthening mechanism. The results indicate that the deformation mechanisms under loading vary among the different honeycomb structure combinations. Among them, the ZAZ configuration exhibited the best bending performance. Foam filling significantly enhanced both the load-bearing capacity and energy absorption performance of all three honeycomb sandwich structures, with an average increase of 17.8% in specific energy absorption. The foam-filled honeycomb composites demonstrated clear advantages in improving structural strength and damage tolerance, offering valuable insights for the optimized design of honeycomb structures.

Honeycomb materials are considered ultra-light materials with excellent mechanical properties due to their unique cellular structure. Their high strength, low density, and excellent energy-absorbing abilities have led to their widespread application in various fields. The star cellular structure is a classical cellular structure proposed by many scholars, exhibiting a negative Poisson's ratio effect. However, due to the susceptibility of the star-shaped units and the vertical supporting rods at the joints to local instability and stress concentration under compressive loads, the buckling of the supporting rods can induce lateral displacement, thereby compromising the overall structural integrity and performance. To address this phenomenon, this study eliminates the supporting rods from the star-shaped structure, specimens of the Improved Star-Shaped Honeycomb (ISSH) were fabricated using Selective Laser Sintering (SLS) technology, followed by uniaxial quasi-static compression experiments and finite element simulations, followed by uniaxial quasi-static compression experiments and finite element simulations. The study investigates whether changes in geometric parameters can enhance the tunability of the structure for different application scenarios. The results reveal that the rod-free star-shaped structure exhibits higher stiffness and strength, and variations in wall thickness and angular parameters significantly influence the structural performance and deformation failure mechanisms. This study enriches the research on star-shaped honeycomb structures.

Structural innovation to significantly enhance the bending performance of sandwich panels under the premise of ensuring lightweight is a major challenge nowadays. This paper introduces a novel assembled honeycomb structure (AHS) for sandwich panels that connects hexagonal honeycomb structures with different Poisson ratios and concave honeycomb structures through double arrows as a transition structure. Sandwich beams with different core-nucleus structures and orientations were prepared by 3D printing and subjected to quasi-static three-point bending tests to systematically reveal the bending evolution mechanism of single honeycomb structures and AHS. Results demonstrate that AHS has superior mechanical and bending properties compared to single honeycomb, where the peak load (PL) is improved by 10.84 % and 15.74 % on average, and the flexural rigidity (FR) can be boosted by up to 25.16 %, but the energy absorption efficiency under large deformations decreases to 63.90 % of single honeycomb. The effect on the energy absorption properties of the enhanced AHS was further explored then by means of localized reinforcement. With only 5.77 % increase in average mass, the total energy absorption capacity of AHS is increased to 1.99 times of the original, and the load-bearing capacity of the structure under large deformation is steadily improved. This study shows that the synergistic design of multiple honeycomb cells and core orientation regulation can break through the bottleneck of the traditional honeycomb performance, which provides a new theoretical support and technical path for the design of high load-bearing and high energy-absorbing sandwich panels.

Honeycomb structures have garnered significant attention due to their outstanding mechanical properties, including high strength, high stiffness, and excellent energy absorption capabilities. This paper innovatively incorporates circular arcs and support structures based on the configuration characteristics of positive and negative Poisson’s ratio cells, designing three novel circular arc honeycomb configurations and their combination forms. Specimens were fabricated using FDM technology. Through uniaxial compression and three-point bending tests, the quasi-static compression and bending properties of these structures were systematically investigated. Finite element simulations provided in-depth insights into deformation mechanisms and stress evolution during compression. Results indicate that the negative Poisson’s ratio with arc and support structure exhibits superior compressive performance, achieving a compressive ultimate strength of 2.6 MPa and a specific energy absorption of 3815.9 J/kg. Compared to conventional honeycomb structures, the specific energy absorption value increased by 3.15 times. Finite element analysis indicates that the arc design effectively disperses stress and enables stable progressive folding. With its high specific strength (6.9 MPa·cm³/g), the negative Poisson’s ratio structure with arcs is suitable for lightweight applications. Bending test results show that the positive Poisson’s ratio arc structure exhibits the highest average crush force (249.1 N) and specific energy absorption (158.8 J/kg) due to arc-induced shear stress dispersion. Combining the three unit cells enhances the mechanical properties of individual cells, with the failure sequence of the composite structure following the strength gradient of the unit cells. This study achieves synergistic optimization of lightweighting, load-bearing, and energy-absorption performance through structural innovation combined with additive manufacturing technology. It provides valuable reference for structural design and application in aerospace, transportation, and building protection fields.