Low Velocity Impact Performance Research Articles

An Experimental Investigation of the Mechanism of Hygrothermal Aging and Low-Velocity Impact Performance of Resin Matrix Composites.

Resin matrix composites (RCs) have better thermal and chemical stability, so they are widely used in engineering fields. In this study, the aging process and mechanism of two different types of resin-based three-dimensional four-way braided composites (H15 and S15) under different hygrothermal aging conditions were studied. The effect of aging behavior on the mechanical properties of RCs was also studied. Three different aging conditions were studied: Case I, 40 °C Soak; Case II, 70 °C Soak; and Case III, 70 °C-85% relative humidity (RH). It was found that the hygroscopic behavior of RCs in the process of moisture-heat aging conforms to Fick's second law. Higher temperatures and humidity lead to higher water absorption. The equilibrium hygroscopic content of H15 was 1.46% (Case II), and that of S15 was 2.51% (Case II). FT-IR revealed the different hygroscopic mechanisms of H15 and S15 in terms of aging behavior. On the whole, the infiltration behavior of water molecules is mainly exhibited in the process of wet and thermal aging. At the same time, the effect of the aging process on resin matrices was observed using SEM. It was found that the aging process led to the formation of microchannels on the substrate surface of S15, and the formation of these channels was the main reason for the better moisture absorption and lower mechanical strength of S15. At the same time, this study further found that temperature and oxygen content are the core influences on post-aging strength. The LVI experiment also showed that the structural changes and deterioration effects occurring after aging reduced the strength of the studied material.

Low-velocity impact performance of 3D-printed PLA/Epoxy/Glass fibers of composite structures and latches

The integration of 3D printing into the synthesis process of polymeric composite structures can offer significant advantages in producing geometrically complex parts. Moreover, engineering components may be subjected to impact loads that can adversely affect their performance and, in some cases, lead to failure. Traditionally, fiber-reinforced composite structures have demonstrated improved responses to applied mechanical loads. In this study, we designed multi-material polymer-based composite structures to enhance structural responses to impact loads. Employing fused filament fabrication (FFF) and solution casting methods, we manufactured PLA lattice infilled with epoxy/Milled Glass Fibers (MGFs) of composite structures with varied MGFs content ranging from 0 to 7.5 vol%. The research provides a comprehensive analysis of the impact behavior of glass-fiber reinforced composite structures, specifically focusing on PLA lattice frames filled with epoxy resin and varying levels of MGFs. Through low-velocity impact tests, the study assesses key parameters such as peak force, peak absorbed energy, residual velocity, and displacement, providing insights into the materials' response to impact loading conditions. The findings highlight the effect of MGF reinforcement on enhancing the impact toughness and resistance to crack propagation, with higher MGF content leading to improved mechanical properties. The microstructural analysis demonstrates the morphology and interface bonding of the composite materials, elucidating the mechanisms. Finally, latches were designed, and their impact behavior was tested to examine the usability of the composite structure in real-life components. The results suggest that the incorporation of MGFs in 3D-printed composite latches significantly enhances their impact resistance, with potential implications for various engineering applications.

Low velocity impact response of Automated Fiber Placement Advanced Placed Ply composites

This study explores the influence of the internal architecture in the low-velocity impact response of Automated Fiber Placement Advanced Placed Ply laminates. AP-PLY laminates with different lay-up are subjected to low velocity impact and compression after impact experiments. Different performance in terms of damage tolerance is obtained as a function of their internal architecture. Triaxial and quasi-isotropic AP-PLY configurations presented a reduced extension of the delamination in comparison to cross-ply panels. As a result, the cross-ply configuration exhibited a drastic loss in residual strength of 49.1% when subjected to 50 J of impact energy. Numerical simulations were employed to provide insight into the deformation and failure mechanisms (e.g., matrix cracking of directly impacted yarns, delamination or tow debonding), and assess the performance of AP-PLY against conventional angle-ply laminates, predicting larger delamination for the latter, showing the potential of the AP-PLY architecture to produce laminates with improved low-velocity impact performance.

Research on the influence of foaming silica gel-filled on low-velocity impact performance of M-type GFRP foldcore sandwich structure

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.

An analytical study on low velocity impact resistance behaviors of general bio‐inspired helicoidal composite plates

AbstractThrough evolutionary processes, helicoidal structures have been proven to exhibit exceptional load‐carrying capacity and impact resistance performance. To date, extensive experimental and numerical studies have been carried out on their impact behaviors, while few relevant analytical studies have been reported even though it is urgently needed for the preliminary assessment of structure design and optimization. In this work, based on the first shear deformation theory (FSDT) and the improved linearized Hertzian contact method, an analytical model for low velocity impact (LVI) performances of helicoidal laminates with arbitrary layups is developed. Therein, the post‐impact damage is taken into account according to continuum damage mechanics (CDM). Comparisons of load‐carrying capacity and energy‐absorbed performance between the proposed model prediction and the existing experimental data\numerical results have been made for verification. Besides, LVI behaviors of conventional laminates with unidirectional distribution andcross‐ply arrangement are discussed. Moreover, the role of rotation angle, impact velocity and the plate dimension on helicoidal laminates' LVI performances are analyzed quantitatively. There is evidence that helical layouts are better able to absorb energy and delay the in‐plane damage.Highlights The LVI responses of bio‐inspired single‐helicoidal (SH) and double‐helicoidal (DH) composite laminate are studied. An effective model to predict the LVI responses considered the post‐impact damage is developed. A comparison of the LVI performance of single‐helicoidal structures with various lay‐up schemes is carried out. DH structure has better low velocity impact resistance than SH structure when the rotation angle shares the same.

Finite element analysis of the effect of crystallinity on low-velocity impact performance of poly (aryl ether ketone) composites

A new copolymer poly (aryl ether ketone) (PAEK) resin was used as a matrix to prepare carbon fiber (CF) reinforced composites with different crystallinity by slow and rapid cooling. Finite element (FE) models were constructed according to micromechanics, and the progressive damage method based on the three-dimensional (3D) PUCK damage criterion was used to analyze the low-velocity impact damage mechanism of the CF/PAEK composites. The experimental results show that the composites with lower crystallinity have higher impact resistance and smaller impact damage area. In the FE simulated impact damage evolution process, the damage of the impact side is mainly compressive damage of the matrix and the fiber, while that of the impact back side is mainly tensile damage of the matrix. Moreover, due to their high interfacial bonding strength, the main damage modes of rapid-cooled composites with lower crystallinity are severe matrix tensile damage and slight fiber tensile damage in the impact back side. However, the slow-cooled composites show more delamination. In addition, for the damage evolution of compression after impact, the FE simulation shows that fiber compression, matrix tension, matrix compression and delamination expand along the transverse to the compression load. Furthermore, the in-plane damage expansion occurs earlier in the rapid-cooled composites, which also have graver interlaminar damage.

Effect of symmetric and asymmetric aluminum arrangements on the low‐velocity impact performance of glass fiber‐reinforced aluminum laminate (GLARE)

AbstractGlass fiber‐reinforced aluminum laminate (GLARE) possesses superior impact performance than both metal and fiber‐reinforced composite. It was found previously that the low‐velocity impact (LVI) performance of GLARE is governed by aluminum at different locations. This implies that reasonably rearranging aluminum in GLARE may bring in some improvements if the functions of different aluminum are all fully played. In this view, the effect of aluminum arrangement on the LVI performance of GLARE was investigated by separately comparing eight symmetric and eight asymmetric GLARE. Finite element analysis was adopted due to its advantage in quantitatively capturing the detailed damage parameters, and it was verified by LVI tests under different impact energy. The LVI performance was elucidated from both impact resistance and energy absorption aspects, where the former included the force and damage responses, and the latter involved the energy absorbed ratio and absorption efficiency. Based on the mechanical and damage parameters, impact resistance and energy absorption factors were proposed for comprehensive characterization. It revealed that arranging aluminum symmetrically in GLARE by placing thinner aluminum in the middle is an effective way to improve its LVI performance.Highlights Aluminum arrangement influenced evidently on the low‐velocity impact (LVI) damage degrees of glass fiber‐reinforced aluminum laminate (GLARE). Impact resistance and energy absorption factors were quantitively defined. Symmetric GLARE with thinner middle aluminum had superior LVI performance. Optimal aluminum arrangement could be simply estimated by energy dissipation.

The effects of graphene oxide addition on low velocity impact performance of aramid fiber reinforced epoxy composites

AbstractIn this study, the impact of incorporating graphene oxide (GO) nanoparticles into the matrix of aramid fiber reinforced polymer (AFRP) composites was investigated. The GO nanoparticles were dispersed in the AFRP matrix at three different weight percentages: 0.1%, 0.3%, and 0.5%. The fabrication of the GO dispersed AFRP nanocomposites was achieved using the vacuum assisted resin infusion molding (VARIM) method, and the AFRP plates were cut using a water jet. The sectioned specimens of the fabricated nanocomposites were subjected to low velocity impact tests. The effects of introducing GO nanoparticles at different percentages were evaluated by analyzing the contact force, deflection, maximum absorbed energy versus time and contact force versus deflection curves. Finally, the key parameters of low velocity impact, including contact force, deflection, and maximum absorbed energy, were compared for the different fabricated AFRP nanocomposites. Based on the results, the AFRP composite with 0.3 wt.% of GO nanoparticles exhibited the best performance under low velocity impact loading conditions. However, the agglomeration of nanoparticles became a significant challenge when higher percentages of GO nanoparticles were added to the composite structure. The findings highlight the importance of determining the optimal percentage of nano materials for incorporation into composite structures.

Using z-pinning to improve the low-velocity impact performance of composite skin/stringer structures

This paper investigates the effect of the z-pin pre-hole inserted (ZPI) process on the impact resistance and post-impact flexural properties of skin/stringer composite structure with different z-pin parameters. The responses of the specimens are characterized in terms of impact denting & cracking length, load-carrying capacity, energy absorption and so on. Experimental results demonstrate that the z-pin cannot inhibit the initiation of debonding cracks at the skin/stringer interface. However, the z-pin forms a bridging traction zone across the cracking and prevent it from developing, which ensures the skin/stringer structure preserve higher peak loading and impact resistance. The specimens with the highest z-pin density have better impact resistance and outstanding residual flexural post-impact properties. Moreover, z-pins play a bridging role through its own failure. One is the inter-fiber debonding and splitting or shear failure of z-pins due to “snubbing effect,” the other is the sliding friction of z-pins and z-pins’ elastic deformation. These results could provide some guidance for designing z-pinning connection of composite skin/stringer structure.

Experimental and Numerical Study on the Low Velocity Impact Behavior of ABR Pipe

The low velocity impact load on pipes during transportation, construction and operation will cause pipeline damage and lay hidden dangers for the safety of pipeline engineering. To study the low velocity impact performance of pipes made of acrylate polymer blended with polyvinyl chloride resin for water supply (ABR), 20 sets of specimens with different heights and different masses of drop hammer were carried out to study the mechanical properties of ABR pipes. Based on the impact time curve, the energy dissipation capacity and impact peak value of ABR pipe specimens were analyzed, and the empirical calculation formula of impact force peak based on the test data is obtained by the dimensional analysis method, with a relative error ranging from −7.8% to 4.1%. Moreover, the finite element numerical simulation of ABR pipe specimens subjected to impact load is carried out, and the strain development law and failure mode of the pipe under low-speed impact load are analyzed. Therefore, the calculation formula of peak impact force and failure mode proposed in this paper can provide safety assessment methods for pipeline engineering designers and constructors.

Low-velocity impact performance of integrally-3D printed continuous carbon fibre composite sandwich panels

Sandwich panels are heavily used in industrial sectors where specific mechanical properties are of utmost importance due to their high weight-stiffness ratio and energy absorption capacity. Lightweight sandwich cores with bio-inspired topologies have been used as an advanced alternative to conventional bulk cores to improve performance. Nowadays, sandwich structures comprised of core and skins are typically manufactured with two different processes and are afterwards adhesively joined together. Here, with a less time-consuming and more efficient assembly procedure in mind, an integrally 3D-printing strategy is proposed. This investigation analyses the low-velocity impact and quasi-static perforation performance of sandwich core designs inspired by the beetle's forewing trabecular structure. It was found that the core material was responsible of the rate dependence observed in the force–displacement curves. More complex finite element models than those employed here are necessary to capture all the fracture modes observed experimentally.

Ageing effect on the low-velocity impact response of 3D printed continuous fibre reinforced composites

This paper aims to analyse the low-velocity impact performance of 3D printed continuous carbon fibre reinforced composites manufactured by fused deposition modelling. Moreover, the effect of ageing on the impact properties and visual damage is studied. This evaluation is crucial for understanding the long-term behaviour and durability of these materials, enabling better design and engineering decisions in various applications where impact resistance is paramount. Low-velocity impact tests were conducted on specimens aged 1, 7, 15 and 30 days. An instrumented drop-weight testing machine was employed for the tests. The dimensions and layup sequence of the composite specimens were designed following the recommendations outlined in the ASTM D7136/D7136M standard for unidirectional composite tapes. Results showed that the initial elastic part slightly reduces with age. In addition, the severity of visual damage in the specimens clearly varied with age. The older specimens present the less visible damage but also the lower impact energy absorption.

Low-velocity impact performance of orthogonal grid reinforced CFRP-foam sandwich structure

Orthogonal grid structures, which are widely used in engineering, are incorporated into the foam to form the grid reinforced core. However, the impact resistance of this type of sandwich structure varies with position. In this paper, the low-velocity impact performance of orthogonal grid reinforced CFRP-foam sandwich structure at different positions was investigated. The drop hammer low-velocity impact tests were conducted at 30 J, 50 J and 80 J energy for the intersection, rib, and center positions, respectively, and the impact resistance of the three positions was further compared with the impact data. The test results showed that the intersection and rib exhibited fiber fracture and delamination of CFRP face and grid, as well as foam crushing and cracking. The center position showed face perforation and foam crushing. At the same impact energy, the intersection position had the strongest impact resistance, with an initial stiffness about 18 % higher than that of the rib, and their peak load per unit mass was higher than that of CFRP-foam sandwich panels, and the center was the weakest. In addition, numerical simulations were performed which were in good agreement with the tests, and the damage processes at different stages were discussed. The lightweight, high impact resistant sandwich structure proposed can provide a reference for structural design.

Low velocity impact performance of natural fibre reinforced polymer composites: a review

Natural fibre-reinforced polymer composites (NFRPC) are versatile and applicable materials for structural applications that require durability and reliability under various forces. However, these composites are susceptible to crack formation when exposed to low-velocity impact (LVI) loads, compromising their functionality and performance. Therefore, it is essential to investigate the influence of LVI on NFRPC and their characterization methods, testing standards, and failure mechanisms. This paper reviews the latest research and development on the characterization, testing, and modelling of NFRPCs under LVI loads. It also explores the impact behaviour of various natural fibres, such as kenaf, bamboo, mallow, buriti, and curaua, and the effect of fibre hybridization and nanofiller incorporation on the LVI response of NFRPCs. The paper evaluates the properties, failure mechanisms, and applications of NFRPCs in relation to LVI resistance. The paper provides useful information for developing advanced composite systems and achieving material efficiency for various structural applications. Finally, it highlights the potential applications and challenges of NFRPC as LVI-resistant materials for advanced composite systems.

Cell-filling reinforced materials for improving the low-velocity impact performance of composite square honeycomb sandwiches: Polymethacrylimide foam vs. aluminum foam

In this study, PMI foam and aluminum foam are used as reinforcement materials for filling the cells of carbon fiber-reinforced composite square honeycomb sandwiches (CSHSs), forming two new sandwich structures, namely, PMI foam-reinforced CSHS (PRCSHS) and aluminum foam-reinforced CSHS (AFRCSHS). The impact resistance and residual flexural performance of the composites is compared by using low-velocity impact (LVI) and three-point bending (3 PB) experiments. The different impact energy levels of 25 J, 50 J, 65 J, and 100 J are applied. The impact and bending failure process and failure mechanism are analyzed using a combination of industrial computed tomography (ICT) and scanning electron microscopy (SEM). PRCSHS and AFRCSHS are compared for various enhancement effects and their resulting lightweight features. The residual flexural and impact resistance properties of the two sandwiches improved significantly. Compared with CSHS, the maximum impact load of PRCSHS and AFRCSHS increased by 115.6% and 78.9%, respectively. Moreover, the impact energy absorption, residual flexural load, and residual flexural energy absorption increased by 30.9% and 21.3%, 80.7% and 58.5%, and 173.1% and 84.3%, respectively. The PRCSHS was noticeably lightweight, but AFRCSHS was not sufficiently lightweight. The qualitative results of comparison of the two reinforcement materials in this study can be extended to other carbon fiber-reinforced all-composite 2D honeycomb sandwiches.

Effect of ageing conditions on the low velocity impact behavior and damage characteristics of aramid-basalt/epoxy hybrid interply composites

Polymer composites reinforced with aramid and basalt fibres are widely used in aviation, automobile, marine and civil structural components. In these applications, composites are often exposed to different environments involving temperature and humidity, which leads to the deterioration of mechanical properties and service life of the structure. This study aimed at investigating the influence of different ageing conditions on the low velocity impact (LVI) performance of 2-D aramid-basalt/epoxy interply composites. Compression molding method of fabrication was employed to prepare the hybrid laminates. LVI coupons were made as per the ASTM D3763 standard and aged in distilled water medium at three different temperatures namely, ambient condition (25 ℃), sub-zero condition (−10 ℃), and humid condition (40 ℃ and 60% relative humidity) until the specimens attain moisture saturation. After ageing, specimens were put through low velocity impact testing at two different impact energies of 10 J and 15 J and results were compared with the pristine specimens. Ultrasonic C-Scan and Scanning Electron Microscopy (SEM) were utilized to analyse the delamination due to impact and micro structural assessment of the pristine and aged specimens. Studies revealed that, specimens aged under sub-zero conditions showed better impact response compared to all other ageing conditions. Furthermore, fibre rupture, matrix decomposition, weakened fibre–matrix interface bonding and delamination were the major damages observed in aged specimens.

Study on Low-Velocity Impact Performance of Coal-Based Carbon Foam Sandwich Structures in Thermal Protection Systems

Coal-based carbon foam (CCF) has been widely used in the hypersonic vehicles’ thermal protection system (TPS) due to its good thermal insulation and mechanical properties. In addition, CCF can absorb large quantities of energy when crushed so that the CCF sandwich structure can effectively improve the impact resistance of the TPS. However, there are few studies on the impact performance of CCF sandwich structures, even the mechanical constitutive model (MCM) of CCF. This research work built the CCF MCM and studied the low-velocity impact properties. A large number of experiments were implemented to establish an effective and comprehensive CCF MCM which has three parts: basic mechanical properties, multiaxial loading failure criteria, and hardening rules. A series of tests on the low-velocity impact performance of two CCF sandwich structures were carried out, and finite element models (FEMs) were established according to the CCF MCM to simulate these tests. The experimental and simulation results were in good agreement. The impact damage mechanism was revealed by the tests and the FEMs. The MCM can be used not only for the simulation of low-velocity impact process but also for failure analysis of other CCF structures, which will help to design CCF structures at a low cost.

Low velocity impact performance of 3D auxetic composites embedded with re‐entrant triangle inclusions

AbstractThis paper reports the low‐velocity impact performance of 3D auxetic composite embedded with re‐entrant triangle inclusions by both experiments and finite element (FE) simulations. Both auxetic and non‐auxetic samples were manufactured by embedding inclusions made from carbon fiber/epoxy laminates into silicone rubber matrix. The pure silicone rubber was also manufactured for comparison. All samples were subjected to low‐velocity impact with an impact energy of 147 J and an impact speed of 5.42 m/s and their impact load‐time and energy‐time curves were compared between the experimental results and FE simulation. The impact performances under different impact energies from 60 to 120 J were further investigated based on the validated FE models. The results show that the auxetic composites show better energy absorption capacity and impact resistance than non‐auxetic composites with the same number of inclusions at all energy levels. More inclusions can result in better impact resistance of auxetic composites when the impact energy is under 120 J. The auxetic composites possess 10% higher crash efficiency than non‐auxetic samples. The embedding of inclusions leads to easier damage of the composite under impact energy of 147 J. The research provides a better understanding on the impact performance of auxetic composites made from random inclusions.

Effect of graphene oxide fibre surface modification on low-velocity impact and fatigue performance of flax fibre reinforced composites

Fatigue and impact resistance are essential performance indicators in structural biocomposites. Integrating multilayer and oxygen-rich graphene oxide (GO) crystals as a fibre surface modification or reinforcing agent in polymer matrix systems have been shown to enhance the interfacial strength and toughness of natural fibre composites. However, the state-of-the-art literature on the GO-modification of composites has focused mainly on their microscale and quasi-static mechanical performance. Here, the fatigue testing results showed that surface modification of flax fibres with GO reduces the slope of the S-N curve by 17% and promotes fibre pull-outs upon failure. Based on the in-situ impact damage analysis, the GO-modification delayed the impact damage initiation and prolonged the stable damage progression phase. The impact perforation energy was similar for modified and unmodified specimens. At kinetic energies below the perforation limit, the GO-modification suppressed the extent of fibre failure and endowed flax-epoxy specimens with better damping performance.

Low-Velocity Impact and Residual Compression Performance of Carbon Fiber Reinforced Composite Stiffened Plates

Low-Velocity Impact and Residual Compression Performance of Carbon Fiber Reinforced Composite Stiffened Plates