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This work aims to study the effects of bionic spiral stacking sequence, impact energy and impactor shape on the impact resistance of laminates. The finite element model is established based on the stress failure criterion, progressive damage evolution, and the triangle traction‐separation law. The reliability of the finite element model is validated through rigorous comparison with experimental data. The study investigates the influence of laminate layup sequence, impact energy, and impactor shape on the impact resistance of laminates. The results show that during low‐speed impacts, laminate damage is primarily characterized by fiber breakage, matrix cracking, and delamination. Matrix cracking and delamination become more pronounced as the impact energy increases. The design of linear spiral ply and power function spiral ply has a positive effect on the impact resistance of laminates. The impact resistance of laminates is sensitive to the sharpness of the impactor and the level of impact energy. Higher impact energy and sharper impactor shapes lead to increased energy absorption in the laminate, resulting in more pronounced damage failure. Highlights: The impact resistance of bionic spiral composite laminates is studied.Three biologically inspired stacking sequences were designed.A numerical simulation method is proposed and verified.The low‐velocity impact characteristics of bionic laminates are revealed. [ABSTRACT FROM AUTHOR]

Structural behavior of precast concrete sandwich panels under low‐velocity drop weight impact is presented in this paper. Three types of concrete panels are considered namely, solid concrete panel (SCP), concrete sandwich panels containing recycled tire crumb rubber as core (CRSP), and expanded polystyrene foam as core (FSP). The panels are reinforced with steel mesh or steel fibers. A total of 12 panels are cast in this study. Six panels are reinforced using steel mesh, and the other six panels are reinforced using steel fibers. The impact test is carried out by dropping a weight from a varying height to input impact energy, which can cause various levels of damage for all specimens. The structural performance is discussed in detail, including failure modes, impact force, deflection, and strain. It is found that the core material greatly affects the structural response of the precast concrete panels. The sandwich panel containing recycled tire crumb rubber performed well in terms of rebounding force, permanent deflections, and damage behavior by partially absorbing the impact energy in both types of reinforced concrete panels. In CRSP and FSP, the maximum deflection to permanent deflection ratio rose from 1.19 in SCP to 2.67 and 2.01, respectively. A decrease of 70% in strain value from the first impact to permanent strain was recorded in CRSP when reinforced using conventional steel mesh. In comparison to its counterpart FSP, the CRSP exhibited a significantly smaller fracture width on the tension face as a result of the core's ability to dissipate impact energy, resulting in lower deflections and less damage to the panel. The CRSP reinforced with steel fibers demonstrated comparable performance to the counterpart FSP in terms of energy absorption and deflection reduction; however, it performed noticeably better than the SCP reinforced with steel fibers by reducing residual deflection by 51.8 mm. Consequently, recycled tire crumb rubber can be used as a sustainable alternative to traditional core materials in precast concrete panels. [ABSTRACT FROM AUTHOR]

The M-type GFRP (Glass Fiber Reinforced Polymer) foldcore was prepared by thermal pressing method, and was bonded with the panel to obtain the complete foldcore sandwich structure and filled the core with polyurethane foam. The influence of foam filling, impact energy and impact position on the damage mode and impact dynamic response under the low-velocity impact of GFRP M-type foldcore sandwich structure is studied through low-velocity experiment. The results show that the impact resistance of N-side impact is better than the B-side impact. Foam filling could effectively closing the gap between the N-side impact and B-side impact. In addition, foam filling could absorb about 15%-25% more energy than the empty core sandwich plate. [ABSTRACT FROM AUTHOR]

A series of experiments is conducted to study energy transfer in a chain of foam disks as a function of temperature. These experiments use two different densities of closed-cell Polyvinyl Chloride foams as an array. A puncture testing machine impacts the chain at a velocity of 1 m/s at five different temperatures. Piezoelectric sensors capture the output and input forces of the chain during the impact, while high-speed cameras record the disk deformations. The chain's energy retention is computed using disk deformations and loading forces. Results indicate that high-density foam chains exhibit significantly higher force and energy retention than low-density counterparts. Notably, the foam's stiffness decreases with rising temperature, more prominently in higher-density foam. However, the proportion of energy retained by the chains remains relatively consistent across different temperatures. Additionally, both foam types show a pattern of exponential decay in energy retention along the chain. These insights offer implications for designing and optimizing energy-absorbing foam systems, paving the way for enhanced energy mitigation in low-velocity impact applications. [ABSTRACT FROM AUTHOR]

A novelty FG honeycomb-reinforced laminate (FGHRL) with viscoelastic material is constructed for an industrial exoskeleton. The study examines how FGHRL dissipates energy under hygrothermal conditions. Low-velocity impacts on the exoskeleton's load-bearing structure are simulated using a spherical object. Parameters for the FGHRL, made of a two-phase material, are estimated using the Halpin-Tsai model and macroscopically uniform theory. In-plane deformations are determined using Reddy's HSDT, while the impact response is evaluated with Newmark-β and Wilson-θ methods. Energy dissipation properties are calculated using the energy balance model, validated through CUF-based FEM and LS-DYNA explicit solution, and factors influencing energy dissipation are investigated. [ABSTRACT FROM AUTHOR]

The M-type GFRP foldcore was prepared by thermal pressing method, and was bonded with the panel to obtain the complete foldcore sandwich structure and filled the core with foaming silica gel. The influence of filling foam, impact energy and impact position on the damage mode and impact dynamic response under the low-velocity impact of GFRP M-type foldcore sandwich structure is studied through low-velocity experiment. The results show that the impact resistance of Node-impact is better than the Base-impact under low energy impact, while the Node-impact is worse than the Base-impact under high energy impact. Filling foam could effectively improve the impact properties of the foldcore sandwich plate and decrease the damage degree of the sandwich plate. In addition, filling foam could absorb about 16–26% more energy than the empty core sandwich plate. [ABSTRACT FROM AUTHOR]

Numerical simulation is significant for investigating impact performance of functionally graded SiCp/Al6061 composite plate. Existing numerical studies rely on stress–strain characteristics derived from theoretical models which hardly consider damage softening and porosity effect. In this work, an effective modeling method is developed to generate geometric models of representative volume elements (RVEs) of SiCp/Al6061 composites. It avoids the limitations of traditional methods in generating RVEs with high ceramic content. Finite element (FE) models for uniaxial compression of RVEs are established with consideration of elastoplastic behaviors of constituent materials and interfacial damage. Stress–strain curves of SiCp/Al6061 composites are obtained from FE simulation results by a homogenization method. The stress–strain curves can reproduce the damage softening, and the predicted elastic moduli agree well with those estimated by Mori–Tanaka theory. Low-velocity impacts of a functionally graded SiCp/Al6061 composite plate are simulated using the stress–strain curves. The simulation results are close to those using stress–strain curves obtained by a theoretical method, however, overestimate contact forces in comparison with experimental results. Novel porous RVE FE models are further developed to consider the porosity effect. The models give an improved prediction for stress–strain characteristics of the composites and low-velocity impact response of the functionally graded composite plate. [ABSTRACT FROM AUTHOR]

Interfacial adhesion properties are a key factor affecting the mechanical properties of composites. It is a very effective way to improve the low‐velocity impact resistance of composites by improving the interfacial adhesion properties. To improve the fiber/matrix interfacial adhesion properties of GF/PA6 (glass‐fiber/polyamide 6) composites, polyethyleneimine (PEI) and γ‐aminopropyltriethoxysilane (KH550) were used to co‐modify GF together in this study. The GF/PA6 composites with different modifications of glass‐fiber (GF) were also prepared using a hot pressing process, and then their flexural strength, shear strength, pendulum impact strength, and low‐speed impact resistance were investigated. Next, the relationship between fiber/matrix interfacial adhesion and mechanical properties of GF/PA6 composites was investigated by combining x‐ray photoelectron spectroscopy, scanning electron microscopy, and x‐ray computed tomography test results. The results showed that the GF‐reinforced PA6 matrix composite with co‐modified GF by PEI and KH550 (PEI‐KH550‐GF/PA6) had the best mechanical properties, with flexural, shear, and pendulum impact strengths of 660.7 MPa, 53.1 MPa, and 261.6 kJ/m2, respectively. Furthermore, the low‐velocity impact resistance was measured in terms of stress peak, absorbed energy, residual stress, and damage extension, and the results showed that the low‐speed impact resistance of PEI‐KH550‐GF/PA6 composites was also substantially improved that the Fmax increased from 7402.1 to 10414.0 N. Highlights: Due to the poor surface activity of GF, in this experiment, GF was co‐modified with PEI and KH550 to achieve better fiber/matrix interfacial adhesion and successfully improve the mechanical properties of the composites;Different modification methods are used to improve the interfacial adhesion of the fiber/matrix interface. The relationship between the interface and impact strength of composites has been studied;The relationship between fiber/matrix interfacial adhesion and internal cracking in composites was investigated using X‐CT and SEM and other test results. [ABSTRACT FROM AUTHOR]

The present work highlights the benefits of matrix strengthening through the inclusion of hard particles within the resin‐impregnated woven Kevlar mat. Aluminium Oxynitride (ALON) particles are added to epoxy resin by 5, 10, and 15 volume percentages. The test coupons were developed through a hand‐lay‐up technique to estimate the low‐velocity impact resistance. The characterization was performed through EDAX and SEM to ensure the presence of the ALON particles and their homogenous distribution respectively. Low‐velocity testing is preferred to assess the capacity of the materials to rebound the incident energy. The damage assessment was made to estimate the material's stiffness. The compression after impact (CAI) was executed to observe the strength of the material after the impact. The post‐CAI micrographic observation reveals the delamination history. The results manifest that the ALON–rich coupon exhibits higher impact resistance to the scale of 33.33% than that of the ALON‐free coupon. The damage assessment and CAI results annunciate the lesser damage and higher compressive strength of ALON‐rich material respectively. The micrographic study studied after the CAI reveals the delamination and failure behavior. Additionally, explicit numerical assessment was conducted to validate the experimental results. A good agreement is attained between the experimental results and numerical predictions. The enriched stiffness of the synthesized material makes it a perfect candidate for structural application where the frequency of impact loading is high. Highlights: Development of ALON reinforced Kevlar‐Epoxy composites for low‐velocity impact applications.Evaluating the performance of developed composites under low‐velocity impact loading.Determining the optimal volume percentage of ALON in the composites.Studying the fractography of developed composites.Correlation between experimental and numerical studies. [ABSTRACT FROM AUTHOR]

Basalt fiber-reinforced composite (BFRC) is extensively used in various fields such as rail transportation and aerospace. However, how to design the structure of BFRC to optimize its impact resistance remains a great challenge. Herein, inspired by the double-twisted Bouligand structure of coelacanth scales, a biomimetic BFRC is prepared. Significantly, the peak impact force of double-twisted BFRC (DT-BFRC) is 3408.12 N, which increases by 48.56% compared with unidirectionally laminated BFRC (UL-BFRC). The maximum residual elastic modulus of DT-BFRC reaches 7.88 J, which is 236.75% higher than that of UL-BFRC. This work offers a promising way to efficiently develop impact resistant BFRC. [ABSTRACT FROM AUTHOR]

AbstractComposite lap joints are essential for various applications, such as aircraft wings, piping networks, sporting equipment, and civil engineering works. Low-velocity impact on such joints is a common occurrence in real-life situations. The response of these joints under such impacts is quite complex. This involves multiple interacting damage modes that include delamination failure, ply failure (in-plane damage), and bond interface (joint) failure. These damages may lead to significant degradation of joint strength without apparent complete failure. Thus, it is very important to predict the response and behavior of lap joints under such impacts. The objective of this study is to demonstrate the methodology for the evaluation of damage parameters for built-in damage progressive models in ABAQUS. By introducing the concept of characteristic length to address mesh dependency, the method ensures accurate and reliable computation of damage parameters. Further, the proposed progressive damage model was improved to include the laminate (in-plane) damage, in addition to delamination and bond failure. Finally, the proposed methodology was validated by applying it to a real-world lap joint impact problem. The present study can be helpful in the initial design phase of composite structures, as it provides a consistent and easy-to-use methodology to evaluate damage parameters for practical impact simulation problems. [ABSTRACT FROM AUTHOR]

The effect of dispersing multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) in the matrix on the low-velocity impact resistance and post-impact residual tensile strength of the carbon fiber reinforced epoxy composite laminates has been experimentally analyzed in this study. The composite specimens with the matrix reinforced by different nanoparticle types and various nanoparticle concentrations (0.1, 0.3, and 0.5 wt.%) were prepared and impacted. The post-impact tensile quasi-static and fatigue tests were performed on the specimens with different configurations to study the influence of aforementioned factors on the impact resistance and damage tolerance. Experimental results show that adding nanoparticles in the matrix increases the maximum impact force, reduces the damage area, and alleviates the dent depth of the laminates remarkedly. Moreover, the improvement in these impact resistances increases with the applied nanoparticle concentrations. The nano-modified composite laminates present higher post-impact static strength and longer fatigue life than the specimens with a neat epoxy matrix. Furthermore, both the post-impact static tensile strength and fatigue life increase with the applied nanoparticle concentrations. The damage areas measured using infrared thermography were found to increase linearly with the applied fatigue cycles for all the studied specimens with various configurations. The damage area growth rates of nano-modified composite laminates decrease significantly as the applied nanoparticle concentrations increase. The MWCNTs present better performance than GNPs in improving post-impact static strength and extending the residual fatigue life, however the effect of applied nanoparticle type on the fatigue damage growth rate is slight. [ABSTRACT FROM AUTHOR]

This paper studies the thermomechanical low-velocity impact behaviors of geometrically imperfect nanoplatelet-reinforced composite (GRC) beams considering the von Kármán nonlinear geometric relationship. The graphene nanoplatelets (GPLs) are assumed to have a functionally graded (FG) distribution in the matrix beam along its thickness, following the X-pattern. The Halpin–Tsai model and the rule of mixture are employed to predict the effective Young modulus and other material properties. Dividing the impact process into two stages, the corresponding impact forces are calculated using the modified nonlinear Hertz contact law. The nonlinear governing equations are obtained by introducing the von Kármán nonlinear displacement–strain relationship into the first-order shear deformation theory and dispersed via the differential quadrature (DQ) method. Combining the governing equation of the impactor's motion, they are further parametrically solved by the Newmark-β method associated with the Newton–Raphson iterative process. The influence of different types of geometrical imperfections on the nonlinear thermomechanical low-velocity impact behaviors of GRC beams with varying weight fractions of GPLs, subjected to different initial impact velocities, are studied in detail. [ABSTRACT FROM AUTHOR]

This research scrutinizes and contrasts the crashworthiness of single-core and two-core corrugated sandwich panels with varying configurations, influenced by crucial parameters like thickness, core angle, and foam filling. Experimental investigations encompass quasi-static compressive loads and low-velocity impact tests on these sandwich structures. Employing the design of the experiment (DOE) method, the study examines parameter impacts on initial peak crushing force (IPCF) and specific energy absorption (SEA) across three sequential steps. The fabrication phase involves creating square and trapezoidal aluminium sandwich panels bonded using specialized aluminium glue. The results notably highlight the pivotal role of corrugated sandwich panel thickness in enhancing crashworthiness, displaying a direct correlation between thickness and responses. Particularly, two-core configurations exhibit superior performance in reducing IPCF during low-velocity loading compared to other panels. These structures showcase exceptional capability in diminishing IPCF rates during low-velocity loading, surpassing even foam-filled panels and demonstrating superior crashworthiness among the tested configurations. [ABSTRACT FROM AUTHOR]

To meet the lightweight requirements of advanced composite materials, the ultralightweight three‐dimensional (3D) braided spacer composites were designed and manufactured by ultra‐high molecular weight polyethylene (UHMWPE). The key structural effects of core column distances and core column heights on the static bending, compression, and low‐velocity impact properties of the composites were further investigated. Results indicated that the mechanical properties of 3D braided spacer composites was closely depended on their structural parameters. The flexure and compression of 3D braided spacer composites decreased with increasing core column distance and core column height. W1/H1 specimen showed the optimal bending and compressive performance. The maximum flexural strength and flexural modulus were approximately 54.77 MPa and 4.95 GPa, respectively. The low‐velocity impact properties were further investigated where the stiffness, energy absorption, and impact resistance of the composite decreased with increasing core column distance. The peak load and energy absorption of the W1 specimen were 2.39 kN and 7.99 J, respectively. While the low‐velocity impact properties increased with increasing core column distance. The H3 specimen exhibited the greatest stiffness, impact resistance and energy absorption with peak loads and energy absorption of 2.81 kN and 8.49 J, respectively. In addition, the macro morphology and scanning electron microscopy (SEM)micrographs were examined to investigate the damage morphology and failure mechanism of the composites. The main failure modes were matrix cracking, interface debonding, fiber buckling, and dislocation, as well as tilting, and failure of the core columns. This work provides guidance for structural design and engineering application of 3D lightweight braided spacer composite. [ABSTRACT FROM AUTHOR]

The rapid increase in use of polymer matrix composites in different industries underscores the need for reliable non‐destructive evaluation techniques to characterize small‐scale damage and prevent structural failure. A novel dielectric technique exploits moisture‐polymer interactions to identify and track damage, leveraging differences in dielectric properties between free and bound water. This technique has demonstrated the ability to detect low levels of damage, but the localization accuracy has not yet been evaluated. This work utilizes unsupervised machine learning to assess the technique's ability to identify the damage boundary following a low‐velocity impact event. Bismaleimide/quartz and E‐glass/epoxy laminates were impacted via drop tower to induce varying levels of damage, and subsequently inspected via dielectric technique at several moisture levels by weight. Resulting data was processed via k‐means clustering and the identified damage boundary was compared to a boundary obtained from backlit images and scanning electron microscopy. Accuracy was quantified using developed metrics for damage centroid and boundary identification. The technique averaged 93.9% accuracy in determining the damage center and 77.5% accuracy in identifying the damage boundary. Results indicated the technique's effectiveness across varying moisture levels, particularly in damage centroid identification. Localization accuracy was shown to be insensitive to moisture content, improving the technique's practical capabilities. Further analysis revealed potential for delineation of delaminations. Highlights: Low‐velocity impact of two material architectures.Damage boundary determined and validated via scanning electron microscopy.Detected damage site via dielectric technique compared to damage boundary.High technique accuracy revealed; >90% centroid localization accuracy.Potential for delamination delineation observed. [ABSTRACT FROM AUTHOR]

Highlights The integration of 3D‐printed cellular cores into sandwich composite structures for load‐bearing applications opens up innovative design possibilities while improving structural efficiency. However, ensuring effective energy dissipation under impact conditions without compromising structural integrity remains a challenge. This study investigates the energy absorption and failure mechanisms of 3D‐printed hexagonal honeycomb sandwich composite structures across three different PLA‐based core materials: polylactic acid (PLA), PLA–Carbon, and PLA–Wood, under dynamic and quasi‐static loadings. Material characterization was conducted via Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Failure modes were analyzed using optical microscopy. The results show that PLA–Wood composites demonstrated significant improvement in energy absorption, absorbing 9.22 J of energy at an impact energy of 11 J, compared to 8.49 J for PLA–Carbon while under in‐plane compression, PLA–Wood recorded an energy absorption of 8.74 J, significantly outperforming PLA–Carbon, which reached only 3.05 J. This improvement is attributed to enhanced interfacial adhesion between the wood filler and the PLA matrix, as confirmed by SEM and FTIR analyses. These findings highlight the critical role of filler compatibility in the structural integrity of 3D‐printed sandwich composites, indicating potential applications in the aerospace and automotive industries, where lightweight and durable materials are essential for improving performance. Dynamic and quasi‐static response of 3D‐printed hexagonal honeycomb cores. Material interactions affect energy absorption through plastic deformation of cores. PLA–Wood outperforms PLA–Carbon in absorbed energy due to filler compatibility. Dynamic loading causes localized core damage with short elastic recovery. Core failure mechanisms with long elastic recovery vary in quasi‐static tests. [ABSTRACT FROM AUTHOR]

Simulating composite material structures requires complex constitutive models, which normally require fine meshes to obtain an accurate prediction of their behavior. Pam-Crash software has been used for several years in the automotive industry and has been proved to be an efficient tool for simulating metallic structures, returning good correlations in a fast computational time. However, constitutive models for composite materials in Pam-Crash present some difficulties: some materials are not able to be suitably modeled and the predictive results depend on the mesh refinement. This work proposes a solution for predicting the progressive damage of composite materials in Pam-Crash, which scales the energy dissipated by the damage mechanisms and checks the viability of modeling the material behavior, taking into account the recommended size of finite elements in the automotive industry. The proposed solution is applied for the simulation of Open Hole specimens to evaluate the ultimate strength consistency. After this, it is applied for the simulation of Compact Tension specimens to check the consistency of crack propagation behavior. By considering the target size of the finite elements in the material card definition, the predictions demonstrate great improvement in the equivalence in results between different mesh refinements. Finally, the solution is applied to simulate impact tests on large structures. Good correlations with experimental data are obtained in fast computational times, making this methodology a candidate for application in composite-related automotive simulations. [ABSTRACT FROM AUTHOR]

Reliable performance of composite adhesive joints under low-velocity impact is essential for ensuring the structural durability of composite materials in demanding applications. To address this, the study examines the effects of temperature, surface treatment techniques, and bonding processes on interlaminar fracture toughness, aiming to identify optimal conditions that enhance impact resistance. A Taguchi experimental design and analysis of variance (ANOVA) were used to analyze these factors, and experimentally derived toughness values were applied to low-velocity impact simulations to assess delamination behavior. Sanding and co-bonding were identified as the most effective methods for improving fracture toughness. Under the identified optimal conditions, the low-velocity impact analysis showed a delamination area of 319.0 mm2. These findings highlight the importance of parameter optimization in enhancing the structural reliability of composite adhesive joints and provide valuable insights for improving the performance and durability of composite materials, particularly in aerospace and automotive applications. [ABSTRACT FROM AUTHOR]

The combination of auxetic behavior with concrete offers promising advancements in structural materials, providing unique mechanical properties that enhance impact resistance and energy absorption. The study investigates the mechanical behavior of auxetic concrete cellular structures, focusing on elliptic and peanut-shaped unit cells as well as their modified stiffener configurations, under low-velocity impact loading. To compare their impact performance, traditional and stiffened models were analyzed numerically using finite element solver ANSYS/LS-DYNA. The findings indicate significant differences between traditional and stiffened models. Stiffened models, such as SEC and SPC, exhibit higher maximum impact forces compared to traditional models like TEC and TPC. The introduction of stiffeners delays the zero-force phenomenon, resulting in extended energy absorption periods. The TPC model absorbed the most significant proportion of the initial impact velocity among traditional models, whereas the SPC model exhibited the highest energy absorption in models with stiffeners. The study highlights the potential of stiffened auxetic concrete cellular structures to enhance impact resistance and energy dissipation, making them advantageous for applications requiring high structural resilience. Further research into varying impact velocities and loading directions is recommended to optimize these structures for diverse conditions. [ABSTRACT FROM AUTHOR]

Optimizing the impact properties of polymer composites is essential in aircraft industries. Hybridization of fibres is one of the efficient methods to enhance the impact properties of polymer composites. Dispersion of nanoparticles into epoxy resin improves the toughness of composites. This study examines the low-velocity impact (LVI) behaviour of hybrid epoxy-based carbon/glass fibre-reinforced laminates. Initially, the epoxy resin was modified with 0, 0.5, 1, 1.5, and 2 wt% of nanoclay and TiO2 nanoparticles using mechanical stirring followed by an ultrasonication method. To investigate the influence of stacking sequences, laminates were fabricated with (90 G/0 G/90 C)S, (90 G/0 C/90 G)S, and (90 C/0 G/90 G)S. The samples used for this study are six-ply symmetric laminates. Laminates were impacted with different impact energies between 30 and 80 J with an impact velocity of 7 m/s to generate damages. The residual strength of damaged specimens is determined using compression after the impact test. The order of stacking, fibre orientation, and the presence of nanoparticles all have a significant impact on the residual strength of laminates. By using C-scan images, layer-wise damage mechanisms were identified. The specimen with (90 C/0 G/90 G)S sequence has very high damage resistance compared to other laminates. [ABSTRACT FROM AUTHOR]

Materials with a negative Poisson's ratio are known as auxetic materials, which are highly desirable for improved resistance to indentation and impact. Angle-ply composite laminates with high anisotropy exhibit auxetic behavior within a specific range of layup angles. In this research, the influence of negative Poisson's ratio on the mechanical response and the enhancement of the damage behavior of carbon/epoxy composite laminates under low-velocity impact has been numerically investigated. For this purpose, a MATLAB code based on classical lamination theory relationships was developed to determine the range of layup angles to achieve both negative Poisson's ratio in-plane and through-thickness (out-of-plane). Then, the layups with the most negative through-thickness and in-plane Poisson's ratio values were selected. Also, two new stacking sequences were investigated so that both of them partially exhibited the characteristic of negative through-thickness and in-plane Poisson's ratio. The progressive damage model is written and implemented using a computer code in the Abaqus user-material subroutine. The progressive damage model consists of Hashin and Puck failure criteria and the damage evolution model based on the equivalent strain method to predict the initiation and evolution of damage for matrix and fiber. The results indicate that the new laminate configurations have 66% higher effective longitudinal modulus and 173% higher effective transverse modulus compared to the in-plane and through-thickness auxetic ones, respectively. In addition, the proposed configurations showed less overall damage under low-velocity impact loading compared to the auxetic laminates. Based on the investigations, the new configurations with features such as high impact force, low impact time, and low maximum displacement could be suitable for use in structures with a hardwall design approach. [ABSTRACT FROM AUTHOR]

Improvement in mechanical properties of fibre-reinforced polymer composites through proper matrix modification has emerged as the significant trend in recent advanced technology. Dispersion of nanofillers in the matrix results in ultra-light weight, high strength, impact resistant and durable structures. In the current investigation, effect of the addition of varying percentages (0, 1, 3, 5 and 7 wt.%) of low-cost nanoclay to the unsymmetrical carbon/glass (C2G8) hybrid composites on mechanical, tribological and low-velocity impact (LVI) behaviour were investigated. Using traditional hand lay-up techniques, nanocomposite specimens were prepared. The results revealed that C2G8 hybrid composite with 5 wt.% loading of nanoclay possessed maximum hardness (35 HV), flexural strength (494 MPa), impact strength (Izod (119.022 kJ m−2), Charpy (563.922 kJ m−2)) and minimum specific wear rate (19.6 × 10−3 mm3 Nm−1) in comparison with other hybrid combinations. LVI test also revealed enhanced energy absorption (112.46 J) for hybrid nanocomposite against plain C2G8 hybrid composite. Furthermore, the damage depth and areas were observed by visual inspection and scanning electron microscope to account for best possible structure–property relationship. Developed hybrid nanocomposite may be considered as a suitable material for various automotive applications. [ABSTRACT FROM AUTHOR]

In this work, the dynamic response of the clamped sandwich beams with fibre-metal laminate face-sheets under low-velocity impact is analytically and numerically studied. Analytical solutions for the dynamic response of clamped FML sandwich beams under low-velocity heavy-mass impact are developed based on modified rigid-plastic material approximation. Analytical results are compared with numerical ones, there is a good agreement between the two. The effects of foam strength, strength ratio of metal layer to composite layer, and composite volume fraction on structural response are discussed in detail. It is shown that foam strength has a substantial impact on the local denting deformation whereas strength ratio of metal layer to composite layer has a considerable impact on the overall bending of FML sandwich beams. [ABSTRACT FROM AUTHOR]

Sandwich composites reinforced with weft-knitted spacer fabrics (WKSF) have a high potential for use in low-velocity impact applications due to the presence of Z-fibers. The present research fabricated sandwich composites using C-glass weft-knitted spacer fabrics and epoxy resin. Three different architectures, i.e., 1 × 1-Rib gaiting, 3 × 3-Rib gaiting, and 5 × 5-Rib, were used to achieve different orientations of Z-fibers. Low-velocity impact test was carried out on the prepared samples. Also, the impact behavior of the sandwich composite was simulated using ABAQUS standard/explicit. The experimental and numerical results show that Z-fibers affect the low-velocity impact behavior of sandwich composites. Based on experiments, the lower maximum reduced acceleration of the impactor and higher contact duration in 3 × 3 Rib-gating means that this specimen has more impact resistance. The indentation percentages of 1 × 1-Rib gaiting, 3 × 3-Rib gaiting, and 5 × 5-Rib gaiting samples were 37%, 34%, and 91%, respectively. In addition, considering the thickness of composites, the experimental indentation of 3 × 3 Rib-gating is lower than other samples which is confirmed by the numerical displacement of the impactor. Numerical analysis showed that the elastic modulus of Z-fibers, its position, and boundary conditions affected stress distribution. The discontinuity among Z-fibers prevents the transfer of stress from the impact area to the outside of this area. Generally, composites reinforced with 3 × 3-Rib gaiting structures show the highest resistance to impact stiffness. [ABSTRACT FROM AUTHOR]

The incorporation of nanoparticles has been recognized as one of the methods of reinforcement of sandwich panels as an effective substitute for popular materials such as metals. This study has examined the low-velocity impact responses of two groups of nanocomposite sandwich panels at different energy levels. Clay-silica nanoparticles and nanoclay-carbon nanotube (CNT) were integrated as nanofillers into the face sheets of sandwich panels. The sandwich panel with glass fibers/epoxy face sheets and a PVC core was fabricated by the hand layup method. The Contact force-time and contact force-displacement curves were recorded at various energy levels of 15, 30, and 50 J. The simultaneous presence of nanoclay and CNT increased impact resistance by 43.2%, 19.8%, and 10.26% at energy levels of 15, 30, and 50 J, respectively, in comparison with the reference sample without nano-particle whereas the presence of nano-silica with nano-clay at some weight fractions weakened the impact resistance. The analysis of SEM images indicates the proper distribution of nanoparticles and the uniform distribution of CNT leading to the increase in impact properties, which are compatible with the mechanical results. [ABSTRACT FROM AUTHOR]

This paper investigates the low-velocity impact response and damage behavior of glass fiber reinforced polymer (GFRP) hollow ribbed emergency pipes of our design under different impact heights. Drop hammer impact tests with impact velocities of 8.41 m/s, 8.97 m/s, and 9.50 m/s were conducted using an impact platform. A progressive damage model for low-velocity impact was developed using Abaqus/Explicit finite element software. The model used the three-dimensional Hashin damage initiation criteria and a damage evolution model based on the equivalent strain method to simulate the initiation and evolution of intralaminar damage in the pipe ring. A cohesive zone model (CZM) based on a bilinear traction-separation law was used to simulate delamination. The results show that the pipe rings experienced fiber or matrix fractures and delamination damage during the impact process. Additionally, the pipe ring specimens underwent bending vibrations under the impact load, leading to fluctuating contact forces at all three impact heights. Analysis of the simulation results reveals that the primary damage modes in the GFRP hollow ribbed emergency pipe are fiber tension damage, matrix tension damage, and fiber compression damage, with delamination occurring mainly in the impact area and the interface area on both sides of the rib. [ABSTRACT FROM AUTHOR]

Highlights In this study, experiments combined with finite element analysis (FEA) were used to investigate the damage mechanism of transverse low‐velocity impacts on three‐dimensional woven tubular composites (3DWTC) with different structures. The damage morphology after impact was observed using three‐dimensional microscopy and scanning electron microscopy (SEM). Three mesoscale models were constructed based on the authentic structure of the 3DWTC. Additionally, the effects of the structure type on the impact resistance, stress distribution, and damage morphology of 3DWTC were studied. The impact resistance of the shallow cross‐linked (SCL) structure is the strongest, according to the data. The structure that resists impacts the least is the through orthogonal (TO) structure. The greater the straightness of the warps in the structure, the density of the weft, the volume fraction, the greater the cooperative load‐bearing capacity of the warps and wefts, and the greater the speed of stress propagation. The wefts and inner warps are subjected to tensile forces at the point of impact. The outer warps are subjected to compression. The stresses are distributed in a cross‐shaped pattern. The straightened warp and weft parts of the TO serve a key structural role in load‐bearing. The warps of the SCL and the shallow‐crossed curved joint (SCCJ) structure serve a key structural role in the load‐bearing capacity. The impact resistance of 3DWTCs was investigated. The tensile state, stress propagation rate of 3DWTC were analyzed using the mesoscale model. The main load‐bearing components are revealed. The differences in damage morphology of 3DWTCs are analyzed. [ABSTRACT FROM AUTHOR]

This paper focuses on the mechanical response and viscoelastic properties of double‐blade composite stiffened structure (DCSS) under low‐velocity impact (LVI). Firstly, the impact resistance and viscoelastic behavior of the DCSS are revealed by LVI testing at four different locations using the same initial velocity. Next, the damage morphologies at the impact locations are observed with ultrasonic A‐ and C‐scan equipment and optical microscopy. At last, the DCSS containing impact damage is implemented for axial compression and the strain values of the DCSS surface are obtained using a strain testing system to reveal its residual properties and buckling behavior. The results show that there are significant differences in the impact damage modes at the four different locations. The maximum impact resistance is observed at location D, while location A has the opposite. The DCSS has a certain viscoelastic behavior at LVI and conforms to an exponential decay model. Moreover, position B presents interface debonding damage due to stiffness discontinuities at the flange and skin bonding and severely weakens the load carrying performance of the DCSS. Highlights: The impact resistance of different positions is analyzed by LVI experimental results.Viscoelastic properties exist at different impact locations and obey the exponential decay model.Impact damage alters the buckling load and residual strength of the DCSS.The damage mechanism of the triangular zone is revealed by damage morphology. [ABSTRACT FROM AUTHOR]

AbstractVaults and dome structures are attractive in architecture due to their ability to evenly distribute weight and support substantial loads without internal columns. Fibre-reinforced concrete is ideal for these compressive structures, which experience low tensile stress. Assessing their performance under impact loading is crucial for safety, financial protection, and preserving cultural heritage. In this study, twelve arch-shaped slabs with thicknesses of 50, 75, and 100 mm, incorporating varying fibre percentages, were tested using a drop-weight impact test machine. Finite element analysis, validated against experimental results, was employed to evaluate the slabs’ behaviour under low-velocity impacts. The analysis revealed multiple flexural cracks in fibre-reinforced specimens, with maximum crack widths decreasing as fibre ratios increased. Although the number of microcracks rose with higher fibre content, crack spacing diminished. Results indicated that adding steel fibres significantly enhances tensile strength and energy absorption—showing a 90% increase in the 100 mm thick dome with 1.5% fibres—while reducing cracking. These improvements contribute to the durability, stability, and safety of concrete domes, lowering maintenance costs. Thus, incorporating steel fibres in the design and construction of impact-resistant concrete domes is highly recommended. [ABSTRACT FROM AUTHOR]

Aluminium foam sandwich panels (AFSPs) have a high impact resistance and are suitable for a wide range of engineering applications. To improve corrosion resistance, this paper proposes an anti-corrosion sandwich panel with stainless steel as the upper sheet. Drop hammer impact tests were performed on a total of ten AFSPs to investigate their dynamic response and failure patterns. To assess the deformation performance of AFSPs, a laser displacement meter was used to obtain the bottom centre displacement. The effects of the impact energy and the thickness of each component of AFSPs on the peak impact force and deformation performance were studied. Test results showed that the thickness of each component had notable effects on the impactor and bottom displacements. In addition, the effect of the unit mass of the components in AFSPs on decreasing the bottom displacement was discussed. Compared to increasing the aluminium foam and lower sheet thicknesses, increasing the upper sheet thickness was more effective in decreasing the bottom displacement. A finite element model of AFSPs was developed to conduct parameter analysis, indicating that impactors with larger diameters resulted in higher peak forces and reduced deformation of AFSPs. [ABSTRACT FROM AUTHOR]

The perforation resistance of ceramic/polyurea composite plates of different structural configurations subjected to low-velocity impacts by differently shaped impactors were investigated. First, a perforation experiment on polyurea sheet and a bending fracture experiment on ceramic sheet were performed, and their numerical simulations were carried out to validate constitutive models and parameters for the polyurea and ceramic materials. Then, numerical models for nacre-like, layered, and encased ceramic/polyurea composite plates subjected to impacts by conical, hemispherical, and blunt impactors were developed. Numerical simulations were conducted to compare failure modes and energy absorption characteristics of the three kinds of composite plates. Numerical results showed that the nacre-like plate was superior to the other two composite ones in energy absorption, especially under the impact by blunt impactor. [ABSTRACT FROM AUTHOR]

This study investigated the low-velocity impact response of titanium-based carbon-fibre/epoxy laminate (TI-CF FML). A comprehensive experimental study was carried out with impact energies ranging from 16.9 J to 91.9 J. Finite element analysis, performed using ABAQUS, was employed to elucidate the failure mechanisms of the laminate. Three distinct damage modes were identified based on the impact energy levels. The energy absorption characteristics of the TI-CF FML were analysed, revealing that maximum energy absorption is achieved and remains constant after penetration occurs. The relationship between impact force and displacement was also explored, showing that the laminate can withstand a peak force of 13.1 kN. The research on the impact resistance, damage mechanisms and energy absorption capacity of TI-CF FML provides an in-depth understanding of the impact behaviour of the laminate and its suitability for various industrial applications. [ABSTRACT FROM AUTHOR]

This study aims to analytically and numerically investigate the dynamic behavior of clamped foam-filled Y-shaped sandwich beams subjected to low-velocity impact. Using the yield criterion for the foam-filled Y-shaped sandwich structure, a theoretical model is proposed. The bound and the analytical solution of low-velocity impact (LVI) of the foam-filled Y-shaped sandwich beam (FYSB) are obtained. Numerical computations are conducted to study the dynamic behavior of FYSB subjected to LVI. Analytical predications are in agreement with numerical. Subsequently, an in-depth analysis is undertaken employing a theoretical model to discuss the influences of parameters such as the Y-shaped plate angle, impact location, foam strength on the dynamic behavior of the FYSB. It is shown that for the given deflection, the impact force diminishes as the impact location progressively approaches the mid-span, and increases with increasing foam strength, Y-shaped plate angle, face-sheet thickness and striker mass. The analytical model can be used to predict the dynamic response of the FYSB subjected to LVI. [ABSTRACT FROM AUTHOR]

The all-CFRP sandwich structure with ultralight honeycomb is designed and manufactured by stretching process. Two scenarios, including global and local impact, are considered to reveal the characteristics of impact resistance. The effects of different impact energies and core densities on energy absorption and failure mechanism are thoroughly discussed. Meanwhile, the post-impact residual compressive strength is carried out to evaluate the influence of impact on structural strength and stability. The results show that under the global impact, the impact resistance is related to core density, and the energy absorption is mainly from honeycomb core. While under the local impact, as the impact energy increases, the failure mechanism of the structure changes from core crushing to penetration. The research provides a guidance for low-velocity impact performance and structural optimization design of sandwich structures. [ABSTRACT FROM AUTHOR]

The aim of this research is to investigate experimentally and numerically the low-velocity impact behavior of foam-based composites reinforced with warp-knitted spacer fabric (WKSF). To prepare different foam-based composites, the structural parameters of WKSFs including cell size, position, and Z-fiber height were considered. A drop weight impact test with an initial energy of 5J was carried out to examine the low-velocity impact behavior of composites, followed by experimental analyses of Mises, shear, and normal stress on various composite components. Thereafter, the impact behavior of the composites was simulated using ABAQUS/CAE software. The comparison between experimental and numerical results showed a maximum error of 9.79% in predicting the acceleration of impactor. In addition, the results revealed significant stress disparities among samples. Stress analysis showed complex patterns across samples, emphasizing structural parameter influence on stress tolerance and load-bearing capabilities. Notably, Z-fibers displayed substantial stress tolerance, while the matrix predominantly undergoes shear stress. Consequently, the ideal structure for low-velocity impact applications includes small cell size, high thickness, and non-facing hexagonal cells. [ABSTRACT FROM AUTHOR]