Low-velocity Impact Tests Research Articles

Effect of polyurea coating on low-velocity impact properties of unidirectional carbon fiber-reinforced polymer composites plates

To improve the impact performance of unidirectional carbon fiber-reinforced polymer composites (CFRP) for engineering structures, a polyurea coating was sprayed on the CFRP surface. Effects of the polyurea spraying position and thickness on the CFRP impact properties were studied using a low-velocity impact test and computed tomography. The results show that the front-coated polyurea layer reduces the impact energy acting on CFRP because of the consumption of impact energy so that the internal damage of CFRP is smaller and retains higher CFRP bearing capacity than that of other spray positions. The rear-coated polyurea layer has a supporting effect on CFRP, thus the plastic deformation of CFRP is reduced and the structural integrity of CFRP is maintained. Under the impact load, the damage mainly occurred inside the CFRP, and almost no damage occurred in the polyurea layer. The damage in CFRP is mainly the split along the fiber direction, and it is trapezoidal and delaminated from the impact surface to the back-impact surface.

Determination of progressive damage modelling parameters and calibration studies of 8-harness satin weave S-2 glass fibre reinforced composites

The aim of this article is to present a progressive damage modelling study of 8-harness satin weave S-2 glass fibre-reinforced SC15 epoxy matrix composites. Extensive mechanical properties of the composite were investigated throughout the study. The material was subjected to low-velocity impact (LVI) loading for investigating progressive damage. MAT162 material model in Ls-Dyna commercial finite element software was chosen for modelling damage that occurred in composite structure at the end of LVI test. MAT162 needs different material properties including elastic and strength properties with additional damage parameters. Different standard and non-standard tests were conducted to obtain these properties. Additionally, numerical simulation studies were run to calibrate these material properties. Finally, a set of calibrated material properties of 8HS-S2G/SC15 composite were obtained.

Low-velocity impact failure of foam-filled GFRP trapezoidal corrugated sandwich structures

In this paper, a new lightweight sandwich structure with polyurethane foam filled glass fiber reinforced polymer (GFRP) trapezoidal corrugated sandwich structure is fabricated. Based on the low-velocity impact tests, the impact failure performance and energy absorption efficiency of polyurethane foam filled sandwich structures are investigated. Low-velocity impact tests were carried out on the node and base positions of the foam filled trapezoidal corrugated sandwich structure by using a drop hammer test machine, and the set impact energy range was 25 J – 150 J. Experimental results show that when the impact energy is the same, the maximum impact load and maximum energy absorption generated by the node impact are greater than the base impact, which proves that the node position has better impact resistance and energy absorption effect than the base position. In addition, by comparing the displacement-time curves of foam filled and unfilled sandwich structures, it is found that when the impact energy is the same, the slope of the displacement-time curve of unfilled specimen is greater than that of foam filled specimen. Therefore, within the same time, the deformation of unfilled specimen is larger than foam filled specimen during the impact process, which demonstrates the effectiveness of polyurethane foam filling on the gain of sandwich structure.

Investigation of the influence of Halloysite Nanotubes (HNTs) on the low-velocity impact behavior of carbon fiber-reinforced epoxy composites

This study explores the impact of incorporating Halloysite Nanotubes (HNTs) nanoparticles on the low-velocity impact (LVI) behavior of carbon fiber (CF) laminate epoxy nanocomposites. The objective of this investigation was to observe the effects of different nanotube loadings (0.5[Formula: see text]wt.% and 0.7[Formula: see text]wt.%) on CF composites and assess their impact resistance. To achieve this, the CF was subjected to Electrophoretic Deposition (EPD) process to introduce the HNTs. Vacuum-assisted Resin Transfer Molding (VaRTM) was employed to fabricate the CF-reinforced epoxy-based laminated nanocomposites with incorporated HNTs. LVI tests were conducted following the ASTM-D-7136 standard, utilizing impact energies of 10[Formula: see text]J and 15[Formula: see text]J. Subsequently, the damaged areas within the composites were examined using optical microscopy (OM) and scanning electron microscope (SEM). The findings of this investigation revealed a significant enhancement in impact damage resistance with the addition of HNTs. The highest damage resistance and minimal energy absorption were observed at a loading of 0.7[Formula: see text]wt.% HNTs. The results reveal that incorporating 0.7[Formula: see text]wt.% HNTs substantially reduces delamination damage, influenced by absorbed impact energy. As well it composite underscores enhanced interlaminar bonding through 0.5[Formula: see text]wt.% and 0.7[Formula: see text]wt.% HNTs modification. Hence, we confidently assert that the addition of HNTs nanoparticles to CF/epoxy composites has considerably influenced the impact response of the nanocomposites.

Low-velocity impact response of a novel bionic turtle shell back armor sandwich structure

Turtle shell dorsal armor comprises a typical lightweight laminated composite structural material, which is constructed by cuticle and bone layer, with high specific strength and high fracture toughness. The red-eared slider turtle, a widely studied species of turtle, has a rich hierarchical structure. In this paper, according to the structure of red-eared slider turtle shell dorsal armor and the characteristics of each layer as well as by taking into full consideration of the fine structure of cuticle and ventral cortex of the shell dorsal armor, two bionic foam silicone rubber sandwich structures of different levels were prepared. Low-velocity impact test and finite element simulation analysis were carried out to study the mechanical response, specific absorbed energy, and damage mode of the two bionic sandwich structures under different impact energies, hammerhead shapes, and hammerhead radii. By comparing the mechanical response and specific energy absorption with the existing ordinary sandwich structure, we find that the two sandwich structures modeled in this paper exhibit better impact resistance than the ordinary sandwich structure. The shape and radius of the hammer head have a significant effect on the energy absorption characteristics of the sandwich structure, and the damage mode under the hemispherical hammer head is mainly dominated by tensile tearing damage, while the damage mode of extrusion fracture is more obvious under the impact of the conical hammer head. With the increase of the radius of the hammer head, the absorbed energy and specific energy absorption of the sandwich structure increases.

Experimental Analysis and Finite Element Modeling of S-Core Sandwich Panel Composites Drop Impact Response

Sandwich panel composites have several applications in material technology. The sandwich panel composite material is constructed of stainless steel-316 for the top and bottom plates, aluminum 1050A-0 for the core, and DP-8405 acrylic adhesive for the binding element. The impact behavior of S-core composite sandwich panels was examined using low-velocity drop impact tests and finite element models. Finite element models have been created to characterize the influence of composite element bending behavior on variations. The specific flexural modulus and strength of composite S-core sandwich structures are equivalent to those found in the literature for core structures. As a result, the minimum weight design served as a guideline for producing weight and density-efficient hybrid composite sandwich panels. The energy absorbed in the test findings rose between 15.15% and 30% as the core thickness grew and between 3.571% and 41.34% as the core arrays changed. Impact load-bearing capability increases with varied core heights and array designs.

Impact response of lightweight steel foam concrete composite slabs: Experimental, numerical and analytical studies.

This paper presents a study on the low-velocity impact response of lightweight steel foam concrete (LSFC) composite slabs. The LSFC composite slab consisted of a W-shaped steel plate, foam concrete and oriented strand board (OSB). Low-velocity impact tests on the LSFC composite slabs were conducted by employing an ultra-high heavy-duty drop hammer testing machine. The tests revealed the failure mode, impact force and displacement response of LSFC composite slabs. The effects of density and thickness of foam concrete and drop height on the peak impact force and energy absorption ratio were investigated. A finite element (FE) model was set up to predict the impact resistance of the LSFC composite slabs, and a good agreement between simulation and test results was achieved. In addition, an equivalent-single-degree-of-freedom (ESDOF) model was set up to predict the displacement response of the LSFC composite slabs under impact loading.

Evaluation of corrugated core configuration effects on low-velocity impact response in metallic sandwich panels

Abstract Sandwich panels are used as body components of vehicles in many sectors, such as defense, aircraft, and aviation, due to their advanced mechanical properties and lightness. This study aims to investigate the effect of core configurations on mechanical performance and deformation behavior of metallic sandwich panels under low-velocity impact loading. For this purpose, metallic sandwich panels having monolithic and sliced core configurations were first produced. Low-velocity impact tests were carried out using varying energy levels (20, 40, 60 J) to examine how the intensity of influence affects the deformation of the sandwich panel. The perforation and deformation behavior on the upper surface plates of sandwich panels were evaluated. Experimental results showed that the core design significantly affects the impact behavior of sandwich panel samples. The sliced core configuration produced approximately 10 % more maximum contact force and absorbed 14 % more impact energy at high-impact energy levels. Additionally, the sliced core configuration delayed core collapse of the core in deformation situations where complete perforation does not occur.

Study of Low-Velocity Impact Behavior of Hybrid Fiber-Reinforced Metal Laminates.

In this paper, the low-velocity impact behavior and damage modes of carbon/glass-hybrid fiber-reinforced magnesium alloy laminates (FMLs-H) and pure carbon-fiber-reinforced magnesium alloy laminates (FMLs-C) are investigated using experimental, theoretical modeling, and numerical simulation methods. Low-velocity impact tests were conducted at incident energies of 20 J, 40 J, and 60 J using a drop-weight impact tester, and the load-displacement curves and energy-time curves of the FMLs were recorded and plotted. The results showed that compared with FMLs-C, the stiffness of FMLs-H was slightly reduced, but the peak load and energy absorption were both greatly improved. Finally, a finite element model based on the Abaqus-VUMAT subroutine was developed to simulate the experimental results, and the damage modes of the metal layer, fiber layer, and interlayer were observed and analyzed. The experimental results are in good agreement with the finite element analysis results. The damage mechanisms of two kinds of FMLs under low-velocity impacts are discussed, providing a reference for the design and application of laminates.

Ceramic based nanocomposites with alumina-carbon nanotube reinforcement for improved energy absorption in sports-related injuries: Microstructural analysis and low velocity impact

This study aimed to investigate the impact of incorporating nanoparticles on the energy absorption properties of nanocomposites using low-velocity impact (LVI) testing and molecular modeling. Various types of thermoset polymer-based nanocomposites reinforced with carbon nanotubes (CNTs) and alumina were analyzed, and the effect of adding two types of nanofillers and microfiber as a filler material was investigated. The results show that the addition of nanoparticles significantly improved the elastic energy absorption properties of the nanocomposites at the atomic level. The LVI tests demonstrated that adding both types of nanoparticles, along with microfiber, significantly enhanced the energy absorption capacity of the four-phase composite under practical conditions. The scanning electron microscope (SEM) analyses revealed the morphology behavior of the nanoparticles. Incorporating both types of nanoparticles simultaneously with the polymer and fibers increased the elastic modulus by up to 163 %. These findings have significant implications for designing structures with energy-absorbing materials to reduce sports-related injuries. The use of nanocomposites with enhanced energy absorption properties can help to improve the performance of energy-absorbing structures and reduce the risk of sports-related injuries.

Evaluation of the low-velocity impact response of high-performance multi-axial warp-knitted flexible composites

This article aims to investigate the dynamic behavior of high-performance multi-axial warp-knitted flexible composite materials under low-velocity impact tests through experiments and numerical simulations. In this paper, high-performance multi-axial warp-knitted flexible composites were prepared. Three different preparation processes, 175°C-5 min, 185°C-10 min, and 195°C-15 min, were designed for the multi-axial warp-knitted flexible composites. Studied the impact response of different preparation processes, initial impact energy, and punch shapes and diameters on materials. The results showed that the flexible composites prepared by various processes exhibit the same impact response curves in the impact resistance process, while the damage morphology and failure modes of the samples are different. Different initial impact energies caused multiple failure modes in the samples. The material showed penetration damage at high energy impacts and permanent depression damage at low energies. For different punch shapes, the impact resistance of materials to hemispherical punches is better than that of cylindrical punches. Numerical simulations were carried out using the finite element software ABAQUS. The custom material subroutine (VUMAT) based on the Hashin damage criterion model was implemented in the finite element program. The experimental and numerical simulation results agree regarding impact response characteristics. This paper analyzes the composite damage shapes, crack extensions caused by low-velocity impact tests and finite element simulation on multi-axial warp-knitted flexible composites. It provides a valuable reference for failure and structural optimization of multi-axial warp-knitted flexible composites for architectural applications.

Investigating Stacking Configuration and Fiber Hybridization Effects on Low-Velocity Impact Behavior in Twill Woven Carbon/Flax Composites

In this study, experimental research has been done to investigate and analyze the effects of fiber hybridization and stacking configurations on the impact performance of carbon/flax bio-hybrid composite laminates. A total of four composite laminates with pure carbon, sandwich, symmetric, and asymmetric stacking configurations were manufactured and investigated in terms of low-velocity impact test with varying energies between 30J and 75J. Both qualitative and quantitative analysis were performed to analyze the damage and failure patterns in the composite layups and were compared with the pure carbon-based layup to identify the effects stacking configuration. The experimental findings showed the symmetric layup having a consistent distribution of flax fiber layers, showed the most enhanced performance as compared to the carbon-based layup Moreover, damage and failure modes differed among layups and increased with varying impact energies. Furthermore, to enable the thorough comparison of the configurations, Composite Performance Index (CPI) was developed, which suggests that bio-hybrid configurations when designed optimally with a suitable number of evenly distributed flax layers, can equal or exceed the performance of a pure carbon fiber configuration.

Influence of graphene nanoplatelets (GNPs) and aluminum-carbon layered double hydroxides (Al-C LDH) in polypropylene matrix of hybrid composite structures on the microstructure and mechanical performances

<p>In this study, a polypropylene (PP) matrix was reinforced with ultra-fine graphene nanoplatelets (GNPs), aluminum-carbon layered double hydroxides (Al-C LDHs), and calcium carbonate (CaCO<sub>3</sub>) as hybrid reinforcements, along with polypropylene grafted maleic anhydride (PP-g-MA) compatibilizers to create a novel thermoplastic-based hybrid composite polymer. The hybrid composite consisted of varying weight percentages of GNPs (ranging from 0.5 to 2.0 wt% in increments of 0.5), 2wt% Al-C LDH, 2wt % CaCO<sub>3</sub>, and 5wt % PP-g-MA. The bulk samples were manufactured using twin-screw extrusion followed by vertical injection molding. The developed hybrid composites were characterized using high-resolution scanning electron microscopy (HRSEM) for microstructural analysis, X-ray diffraction (XRD) for phase identification, X-ray photoelectron spectroscopy (XPS) for compositional analysis, and Fourier-transform infrared spectroscopy (FTIR) for functional group identification. Thermogravimetric analysis (TGA) was performed to assess thermal stability, crystallization, and melting behavior. Mechanical tests, including tensile, compressive, and three-point bending, were conducted to evaluate mechanical properties, while a low-velocity impact test assessed impact resistance. The results showed that the hybrid composite with a PP matrix embedded with 1.5 wt% GNPs, 2 wt% Al-C LDH, and 2 wt% CaCO<sub>3</sub> exhibited improved mechanical properties, achieving an ultimate tensile strength of approximately 45 MPa. This enhancement is attributed to the effective interconnection, bonding, and cross-linking of the reinforcements with the PP matrix, facilitating efficient load transfer, which makes it suitable for structural applications.</p>

Investigating the energy absorption properties of sandwich panels filled with shear thickening fluid with a weight fraction of 35% under low-velocity impact

This research study the energy absorption performance of aluminum core honeycomb sandwich panel (ACHSP) with filled and empty cores subjected to low-velocity impact testing, with diverse skins; (i) aluminum sheets, (ii) 5-ply epoxy glass composite, and (iii) 5-ply shear thickening fluid (STF)-impregnated glass fabrics. The prepared STF was 35 wt% and the impactor heights was selected at 100 and 500 mm to assess the effect of different impact velocities on the energy absorption capability of STF. The specific energy absorption (SEA) of the STF-filled ACHSP with 5-ply STF-impregnated fabrics skin (height of 500 mm) compared to STF-filled ACHSP with aluminum sheets skin and 5-ply epoxy glass composite skin have increased by 28.38 and 21.79%, respectively. In a fact of truth, when the external force is applied to the STF-filled ACHSP, the fluid transitions from a low-velocity to a high-velocity state instantly. This transition exerts forces on the suspended particles within the fluid. Actually, during the impact, the particles come into close contact and form temporary particle networks or chains. These networks increase the viscosity of the fluid, making it resistant to flow. The energy of the impact is then absorbed by the formation and reformation of these particles’ networks. However, the SEA of STF-filled ACHSP at the height of 500 mm to empty ACHSP at the height of 100 mm have decreased significantly, and the energy absorption of STF-filled ACHSPs to corresponding empty ACHSPs have increased remarkably.

A comparative study on the low velocity impact behavior of UD, woven, and hybrid UD/woven FRP composite laminates

This study is aimed at comparing the response and damage of unidirectional (UD), woven fabric (WF) and hybrid UD/WF fiber reinforced polymer (FRP) laminates subjected to low velocity impact. The unidirectional tape and/or woven fabric (plain weave) carbon/epoxy prepregs are laminated and hot-pressed to produce UD, WF and sandwich-like hybrid UD/WF specimens. Impact responses of specimens are determined through low velocity impact (LVI) tests with impact energies of 10 J, 17 J and 25 J. After the LVI tests, the damage of specimens is characterized and analyzed using a combination of visual inspection, ultrasonic phased-array inspection, micro-computed tomography (CT) inspection, cross-sectional microscopic observation, and thermal de-ply test. Also, the LVI damage mechanisms of the three types of specimens are quantitatively compared by using the inter fiber crack volume ratio, total delamination area and fiber fracture length. It is concluded that the fiber architecture plays an important role in determining low velocity impact behavior of composite laminates. Especially, for the sandwich-like hybrid UD/WF laminates whose surface is a WF layer and the core is a UD layer, the WF layer on the surface plays an important role in reducing matrix cracking, delamination and fiber fracture, thus improving its LVI resistance.

Effect of nano hybrid additives on low velocity impact responses of aramid composite plates: example of CNT and ZrO2

Aramid reinforced composites are advanced materials that are widely used in many industrial applications thanks to their combination of high strength and lightness. Nano additives are of great importance for improving the mechanical properties of aramid reinforced composites and reducing costs. In this paper, multi-walled Carbon Nanotube (CNT) and Zirconia (ZrO2) nano hybrid additives were used to determine the effect on the mechanical characterization of aramid composite plates. Therefore, low velocity impact responses of aramid fiber reinforced composites were investigated by adding ZrO2 and CNT nano hybrid additives to the Polives 701 polymer vinylester resin matrix. Low velocity impact tests were carried out at 10 J and 15 J. As a result of the experiments, the effects of nano hybrid additives on the impact absorption properties of aramid composite plates were determined. By determining the maximum force, displacement and time values, the effect of CNT and ZrO2 nano hybrid additives on the impact resistance of the composite plates was analyzed. In addition, it contributed to the development of composite materials used in industrial applications by providing information on increasing the performance of composite materials by using nano additives. As a result of this study, it was determined that the strength of the composite material increased proportionally when the CNT additive was used, and the material became embrittled when the ZrO2 additive was used.

Experimental investigation on low-velocity impact behavior of glass, Kevlar, and hybrid composites with an elastomeric polyurethane matrix

Low-velocity impacts represent a critical dynamic condition for engineering structures. Combining two reinforcing fibers in a single matrix, i.e., hybridization, is considered a feasible way to improve composite performance. In this context, this paper presents an experimental work on composites with Kevlar and glass fabrics and a novel thermoset polyurethane matrix. The coupons are manufactured by vacuum infusion technique and low-velocity impact tests are carried out. First, the impact behavior of Kevlar and glass laminates of different thicknesses is assessed, and then impact tests are performed on different configurations of hybrid laminates, both symmetric and non-symmetric. For the non-symmetric specimens, impact tests were conducted on both sides of the stack. Load vs displacement curves are reported along with absorbed energy. To investigate the damage mechanism, the front, back, and cross-section views of the specimens are analyzed, and features related to the stacking sequences are discussed. Thermographic analyses are carried out on the impacted specimens to further analyze damage. The failure mechanisms are different from traditional epoxy composites and a hybridization effect is reported. The results evidence that the hybrid coupons are viable for structural applications, being capable of absorbing high-impact energies, in particular, non-symmetric hybrid laminates outperformed the Kevlar, glass, and symmetric ones, absorbing roughly 15% less energy for the highest energy impact.

Response and damage mechanism of carbon/aramid intra-ply hybrid weft-knitted reinforced composites under low-velocity impact

Carbon and aramid fiber hybridization is an effective method to improve the impact toughness of composites, thus this paper attempts to develop carbon/aramid hybrid weft-knitted reinforced composites to improve the impact resistance of carbon fiber composites. Three hybrid and two non-hybrid weft-knitted reinforced composites employing carbon and aramid bundles were prepared. Low-velocity impact tests at different impact energies were performed, and the impacted samples were analyzed for visual and internal damages utilizing a three-dimensional optical microscope, ultrasonic C-scan, and micro-CT to explore the damage mechanisms. The results demonstrate that the knitted stitches and loop configuration affect the peak load, deflection, and damage crack initiation and expansion of the composites. The alternating configurations of carbon and aramid fiber in the in-plane and thickness directions incorporate the advantages of the high strength of carbon fibers and the toughness of aramid, exhibiting good impact mechanical properties and damage tolerance. The tight loop laminated structure had excellent impact resistance, with prominent peak loads and tiny damage volumes, but it encountered internal delamination and loop breakages.

Experimental and simulative investigation on the mechanical behavior of GFRP T‐joints subjected to low‐velocity‐impact and post‐impact tensile loading

AbstractTo investigate the failure mechanism of the composite T‐joints subjected to low‐velocity‐impact (LVI) loading varying impact locations, a methodology composed of improved conventional vacuum‐assisted resin infusion (VARI) and LVI testing based on ASTM D 7136 is developed and employed. Moreover, the simulation is conducted to mainly reveal the damage evolution of interlaminar delamination between web and web/skin laminate based on surface‐based cohesive behavior in the commercial software of Abaqus 2020. Further, the effect of LVI loading with various distances from the web laminate to the impact location on the mechanical property and failure mode of the composite T‐joints are presented and discussed as well. By comparison, larger vertical cracks and higher residual tensile strength are found in the T‐joints impacting the corner. However, the T‐joints with the impact point near the corner have lower residual tensile strength and suffer more interlaminar delamination in the interface between web and skin, which is the most critical position of failure.Highlights GFRP T‐joints are manufactured by the vacuum‐assisted resin infusion process with a newly designed mold. The damage evolution in low‐velocity‐impact tests is presented via the quasi‐static tests and finite element simulation. Larger vertical cracks and higher residual tensile strength are found in the T‐joints impacting the corner. The T‐joints with the impact point near the corner have lower residual tensile strength. Interlaminar delamination in the interface between web and skin is the most critical factor of tensile failure.

Low-velocity impact-resistance of aramid fiber three-dimensional woven textile-reinforced thermoplastic-epoxy composites

The development of impact-resistant composite materials for protective applications such as helmet and body armor has attracted considerable attention. In this study, a novel aramid fiber-woven thermoplastic-epoxy composite was developed. Furthermore, three types of woven textiles, namely three-dimensional (3D) orthogonal-woven (3DOW), 3D angle-interlock woven (3DAIW), and two-dimensional plain-woven (2DPW) textiles, were used as reinforcement structures. To study the effect of the woven structure, impact energy, and damage repairment on impact-resistance performance of these composites, low-velocity drop-weight impact tests with various impact scenarios, such as single-impact, repeated-impact, as well as multiple-impact with hot-press damage repairment, were conducted. The results revealed that the woven structure exhibited an obvious effect on the composite impact-resistance performance and failure modes when subjected to specific impact scenarios. For the single-impact scenario, especially under high impact energy levels (10 and 20 J), the 3DOW structure exhibited superior impact-resistance performance as well as damage tolerance, followed by 3DAIW and 2DPW structures. Furthermore, 3DOW achieved superior impact-resistance to the other two structures for the 10-J repeated-impact scenario. The 3DAIW structure, in which debonding or delamination as well as severe resin cracks dominated, achieved superior impact-resistance to multiple impacts with damage repairment.