Low-velocity Impact Response Research Articles

Nonlinear low-velocity impact response of sandwich beams with FG porous aluminum core reinforced by GPLs

Sandwich beam structures facing low-velocity impact frequently throughout their life cycle, making it necessary to investigate the impact response of these structures to enhance their design and reliability in service. In this paper, sandwich beam structures subjected to nonlinear low-velocity impacts are investigated, comprising a functionally graded (FG) porous aluminum core reinforced by graphene platelets (GPLs) and two aluminum alloy face sheets. The mechanical properties of FG-GPLRC core are predicted by a generalized Halpin-Tsai model, which takes porosity into account, where the material properties of the closed-cell aluminum alloy foam are established on experimental data. The numerical investigations are conducted using the finite element method and apply the Hertz contact law. The simulation results indicate that the FG-X pattern, where the porosity coefficients are designed to have the maximum values at the top and bottom layers, while to have the minimum values at the mid-plane layers, exhibits the best impact resistance, and that the incorporation of GPLs enhances the impact response. Furthermore, the findings suggest that the thickness of the core has no impact on the duration of the initial impact. Moreover, an increase in impactor velocity, density and radius results in an increase in both deflection and contact force.

Assessment of low-velocity impact response of a hybrid carbon-aramid braided composite by algorithmic quantification of volumetric structures

This work investigates the impact response of a hybrid two-dimensional (2D) tubular braided composite through an ex-situ examination of its internal structure. An inter-ply hybrid laminate of biaxial braided carbon and aramid layers was manufactured. The sample underwent split Hopkinson pressure bar (SHPB) impact testing, where the applied energy induced barely visible impact damage (BVID). Volumetric representations of the sample were created before and after impact testing using micro-computed tomography (µCT). Novel algorithms were developed to assess properties of the braided composite sample. First, voids in the sample before and after impact were identified through a series of image processing techniques, after which various void properties were extracted. Each void was then matched between datasets to track property change caused by impact. Next, damage in the sample after impact was identified through another series of image processing techniques, then quantified and characterized in the context of the full sample. Statistical analyses in the form of paired-sample t-tests were performed for void properties and overall surface topologies. Additionally, measurement of 3D strain within selected regions of the sample was performed using digital volume correlation (DVC). Results showed that the impact damage did not cause significant void enlargement, but instead caused surface topology shifts, particularly at the inner surface, owing to plastic deformations caused by impact damage, which were primarily caused by delamination and developed from large voids at the site of impact. The hybrid material configuration exhibited a phenomenon where the inner and outer layers minimized cracking in the middle layer, causing plastic deformation to be the primary impact response of the middle layer. Through the analysis processes developed in this work, quantitative assessment of tubular braided composites was achieved by measuring changes in voids caused by impact at the individual level, and by examining the damage profile while accounting for the voids. The methodology can be applied to various material configurations to provide meaningful insight into the effects of hybridization in the impact response of braided composites.

Performance of hybrid Innegra-carbon fiber composites

In this work material synergy with high stiffness carbon fiber with ductile high strength polypropylene fiber (Innegra S), (referred to as Innegra, herein) have been evaluated in a range of laminate designs. Both woven and discontinuous carbon fiber have been considered. The discontinuous fibers are based on three-dimensional deposition (3DEP) (referred to as 3DEP, herein) carbon fiber preform process. Eleven (11) variants of Innegra-carbon fiber hybrid laminates were investigated for tensile, flexure, compression, in-plane shear and low velocity impact response. The effect of position of Innegra within the laminate was studied and found to influence strength and stiffness properties. In terms of overall trends, Innegra provides upward of 18% improvement in strain (ductility) to the composite and eliminates brittle fracture of carbon fiber. The moduli trends follow the proportionality of Innegra fiber to carbon fiber plies. However, the strength is controlled by the interface between Innegra and carbon fiber. The primary failure mode in tension and compression is via onset of debonding between Innegra and carbon fiber. The 3DEP carbon fiber constituents provided highest values of in-plane shear indicating that three-dimensional (3D) network of carbon fiber provides higher shear resistance. The Innegra intensive variants exhibited superior energy absorption under low velocity impact, at energy levels 15–60 J. This work provides insight for designers to incorporate Innegra and carbon fiber hybrids in composite structures.

Drop-weight Impact Responses of Kenaf Fibre-Reinforced Composite-Metal Laminates: Effect of Chemical Treatment and Fibre Composition

Recently, fiber-metal laminates have gained high attention from material scientists and engineers, particularly when it comes to impact-critical applications. When compared to metallic alloys and composite materials, fiber-metal laminates offer several distinguishing advantages. This work intends to evaluate the low-velocity response of kenaf fiber-reinforced polypropylene metal-composite laminates with various fiber compositions, in line with the current trend of using natural fiber as possible reinforcement in composite materials. In addition, a comparison was made between the low-velocity impact response of non-treated and chemical-treated kenaf fiber-reinforced composite-metal laminates. A hot molding compression technique was employed to fabricate the laminates. Low-velocity impact tests were performed based on ASTM D7136 to determine the peak force, maximum displacement, and energy absorption of the materials. The results confirmed that NaOH treatment and increased fiber content resulted in a higher peak force of NaOH-treated kenaf-based metal laminates. For NaOH-treated laminates, the peak force of laminates with 70 wt% was found to be 11.20% higher than laminates with 50 wt% at the impact energy of 60 J. At fiber content of 70 wt%, the peak force of NaOH-treated laminates is 2.14% greater than that of untreated laminates when subjected to low-velocity impact with an energy level of 60 J. However, laminates with low fiber content and without NaOH treatment manifested higher maximum displacement and energy absorption due to the ductile behavior of such materials.

Experimental investigations on the repeated low velocity impact and compression‐after‐impact behaviors of woven glass fiber reinforced composite laminates

AbstractIn this paper, the repeated low velocity impact responses and compression‐after‐impact (CAI) behaviors of woven glass fiber‐reinforced composite laminates were studied at the same total impact energy. Three types of impact energies, 30, 40, and 60 J, were chosen for the repeated impact tests relative to the single 120 J impact event. The impact behaviors including impact contact force–displacement and energy–time curves during the impact testing were recorded. The variations of the impact mechanical characteristics such as peak impact force, maximum displacement, and energy absorption were evaluated. The methods of visual inspection and stereo microscope were applied to identify the damage morphology of the impacted laminates. The damage accumulation was evaluated employing the absorbed energy fraction and normalized maximum displacement. It was found that the influences of impact energy on the repeated impact mechanical response are more remarkable than that of the impact number, and the impact events with fewer impact numbers cause more damage to the laminates for the same accumulative impact energy. Furthermore, the load–displacement and the CAI strength versus impact number curves were compared for the CAI testing. The ultimate load and the resulted CAI strength decrease with the increase of impact number owing to the influence of damage accumulation in repeated impacts.Highlights Repeated impact responses were studied at the same total impact energy. The impact energy makes significant influence on the impact dynamic responses. The impact events with fewer impact numbers cause more damage to the composites. The CAI behavior was explored considering the effect of damage accumulation. The CAI strength of damaged laminates decreases with impact number increasing.

Dynamic response of chain mail fabrics with variable stiffness

Variable stiffness fabrics have gained considerable attention due to their advantages in repeatability, deformability, and controllability of stiffness. However, existing variable stiffness fabrics are limited in fitting complex geometrical surfaces and understanding their dynamic mechanical response. This study aims to address these gaps through experimental testing and numerical simulations. Three fabric samples with different single-cell particles were fabricated to investigate the low-velocity impact response of variable stiffness chain mail fabrics. Impact tests were conducted on the fabrics using small balls at three velocities (2.5 m/s, 3.8 m/s, and 4.8 m/s) to analyze the influence of confining pressure variation on the mechanical properties. The results demonstrate that the impact resistance of chain mail fabric significantly improves as the confining pressure increases from 0 kPa to 60 kPa. That fabric consisting of traditional rings velocity decay value increased from 19.3% to 50.2 % at an impact velocity of approximately 4.8 m/s. Notably, the fabric composed of octahedral particles exhibited limited resistance to ball impact without applying confining pressure. However, when a pressure of 60 kPa was applied, the fabric effectively resisted ball impact and caused upward ball velocity. Multiple impact tests on single-layer fabrics and single impact tests on double-layer fabrics confirmed that fabrics consisting of square ring particles demonstrated better resistance to multiple impacts. The degree of interlocking within the topological interlocking structure, influenced by confining pressure, emerged as a crucial factor contributing to enhanced impact resistance. Numerical simulations revealed that the application of confining pressure promoted the formation of new contacts between interlocking particles. The number and quality of these contacts directly affected the overall mechanical properties, resulting in a solid-like structure. This research provides novel insights for developing structural fabrics with fast, reversible, and controllable stiffness adjustment characteristics.

Low velocity impact on fibre metal laminates: A review

Even though several works are available on the analysis of low-velocity impact (LVI) on fibre metal laminates (FMLs), there is still scope for a better understanding of the complexities associated with their analysis, making it an important area of research. Therefore, it is essential to compile and present the state-of-the-art research in this area to make the critical information available in one paper, facilitating future research. This paper thus covers the detailed review of the articles published on the LVI response of fibre metal laminates (FMLs) based on experimental, numerical and analytical approaches and the associated damage mechanisms under different impact conditions. The discussions can be mainly categorized into two broad groups, namely geometrical and material-based parameters, which significantly influence the structural response of FMLs upon impact. Additionally, the paper compares various numerical techniques reported to model the impact behaviour of FMLs, along with an overview of analytical models. Based on the manufacturing techniques and material constituents of FMLs, the paper discusses feasible methods of improving the performance of impact-prone structures. The exhaustive review of the literature finally concludes that there are scopes of investigating some of the important and relevant areas related to LVI of FMLs like the influence of relative mass of impactor and target and accurate determination of contact stiffness for accurate estimation of interface delamination. Investigating the LVI performance of advanced sandwich structures with FML facesheets is a potential area of research in this direction.

Low-velocity impact response of sandwich panels with layered-gradient metal foam cores

The low-velocity impact response of square sandwich panels (SPs) with three-layer metal foam core was examined via analytical and numerical approaches. Taking into account the core arrangements, the analytical model is formulated by employing an innovative yield criterion, to predict the impact force and deflection responses. The accuracy of the analytical predictions was confirmed through finite element (FE) results, and the influences of the core distribution, impact position, as well as core thickness on the impact behaviour of SPs were discussed. It is shown that the graded core SP exerts slightly inferior impact resistance than the uniform core SP. The closer the impact position is to the clamped boundary, the smaller the deflection of the bottom face-sheet and the greater the impact force. As the thickness of the core increases, the proportion of energy absorption attributed to the core also increases. Eventually, the analytical formula was used to generate a design chart for the lightweight configuration, providing geometric optimization pathways.

Experimental and numerical study of low-velocity impact damage in sandwich panel with UHMWPE composite facings

This paper is concerned with the low-velocity impact (LVI) response behaviour of sandwich composite panels (SCPs) with ultra-high molecular weight polyethylene (UHMWPE) composite facings and Polyvinyl Chloride (PVC)/Polyethylene Terephthalate (PET) foam cores. A series of LVI tests with SCPs subjected to 50 J, 80 J and 110 J were conducted to examine their impact characteristics and damage mechanisms. LVI-induced internal damage in the SCPs were characterised by compute micro-tomography (μCT) analysis. The effects of UHMWPE areal density and foam type on the LVI responses and associated failure modes of the panels were also examined. The experimental results showed that the SCP with a PET foam core exhibited higher impact strength and energy absorption performance than those of the panel with a PVC foam core. In addition, a finite element (FE) model incorporating the Puck’s failure criteria, cohesive law and crushable foam plasticity model was developed and validated to predict the intra- and inter-laminar damages of SCPs. Finally, several failure mechanisms (fibre failure, matrix cracking and local delamination) of SCPs during LVI was thoroughly discussed. The results show the UH170-PET specimen has the best impact resistance and energy absorption performance. The parametric analysis of the areal density and foam type has revealed that these parameters can be optimised for the best LVI resistance of SCPs. These findings are helpful for designing lightweight foam-based sandwich composite structures with superior impact resistance.

Experimental and multiscale investigation of the elastic and impact properties of glass fibers/Elium acrylic modified nanoparticles laminate composites

The mechanical behavior of the laminate composites based Nanostrength®M53 or Graphistrength® CW2-L A1 at different weight fractions (wt%) was studied. An experimental procedure and a numerical simulation were used for the characterization of the microstructures. The Young modulus decreased with the addition of Nanostrength whereas it increased up to 2 wt% and then decreased, in the presence of Graphistrength. The impact response at 10 wt% of the Nanostrength was better in terms of load peak and absorbed energy. The variation of the Young modulus mainly depended on the weight fraction of the nanoparticles, the dispersion state and their initial characteristics. The same observations have been mentioned for the low velocity impact response.

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.

A numerical study on the low-velocity impact response of hybrid composite materials

Composite materials are advanced engineering materials with superior properties to traditional materials. One of the most important disadvantages is the high cost of composite materials. Therefore, producing composite materials from the first to the last stage is a very important process. Homogenization is the most important parameter in production since composites contain more than one material type in their structure. In addition, composite structures are sensitive materials against low-velocity impacts. In this study, the effect of reinforcement material combination and stacking sequence on mechanical properties used in the production of composite materials was investigated by low-velocity impact simulations using LS-DYNA software. The mass of the 12 mm diameter spherical impactor used in the analyzes was determined as 10 kg and low-velocity impact tests were applied at 20 J, 30 J and 40 J energy levels. The composite samples were modeled with 180x100mm dimensions and the contact between the impactor and the sample was made from the center of the composite structure. Numerical analyzes were performed using the Tsai-Wu damage criterion in the LS-DYNA software, and material properties were defined using the "Mat_Enhanced_Composite_Damage (MAT 055)" material card.

Low-velocity impact response of thermoplastic composite sandwich panels with the intersected corrugated core

Thermoplastic composite corrugated sandwich panels (TPC-CSPs) with light weight and high damage tolerance are becoming one of the popular choices for impact protection structures in the marine and aerospace applications. In this work, intersected corrugated sandwich panels (ICSPs) of the same thickness as regular corrugated sandwich panels (RCSPs) were fabricated using simple but efficient slotting and interlocking methods. The impact response and damage mechanisms of ICSPs and RCSPs with different impact locations under various impact energy were obtained through a series of low-velocity impact (LVI) tests. The results show that impact on the long span causes greater structural damage to the RCSPs, while the ICSPs can maintain good integrity after unloading. In the case of 200 J impact energy, the peak force of ICSPs is 15.3 % and 21.4 % higher than that of RCSPs-SS and RCSPs-LS respectively, and has a comparable energy absorption capacity to RCSPs. The finite element (FE) model was established to analyse the response process of the structure and to explore the effect of staggered angles on the deformation and load-carrying capacity. The ICSPs are considered to have better impact resistance and could provide a new idea for the protection structure design.

Mechanical behaviour of hybrid FFRP/aluminium honeycomb sandwich structures

The combination of lightweight properties and high energy absorption capacity makes sandwich structures suitable for applications in transportation industry, such as automotive, aerospace, and shipbuilding industry. In these fields, the gas emissions reduction, fuel saving, vehicle safety and load capacity increase are currently important requirements. This research deals with the study of the mechanical behaviour of a “green” hybrid honeycomb sandwich structure made by an aluminium honeycomb core and flax fibres reinforced skins. Specific interest has been addressed to their mechanical behaviour in terms of bending properties and low-velocity impact response. For the impact tests, two indenters having hemispherical geometry with a diameter of 10 mm (H10) and 20 mm (H20) were selected. The results were compared with other hybrid structures analysed in previous studies. The static three-point bending tests produced different collapse modes, depending on the support span distance. Non-destructive evaluation was carried out for failure mode analysis by optical microscopy and digital radiography (DR). In the aluminium-flax hybrid sandwich structures it is found an increase in the impact strength of 25 % compared to the unreinforced aluminium honeycomb sandwich structures. In terms of specific energy absorption (SEA), it is interesting to underline an increase of 50 % compared to traditional AHS structures.

Low-velocity impact response and compression behaviour after the impact of 3D-printed CCFR self-sensing honeycomb structures

Continuous-carbon-fibre-reinforced (CCFR) honeycomb structures with self-sensing abilities were fabricated by three-dimensional (3D) printing. Pure polylactic acid (PLA) honeycombs of the same size were also fabricated for comparison. Low-velocity impact (LVI) tests and compression after impact (CAI) tests were conducted. Cone beam computed tomography (CBCT) and scanning electron microscope (SEM) were employed to investigate the corresponding damage mechanisms. The LVI test results showed that the presence of continuous carbon fibre effectively inhibited the generation and propagation of the damage in the matrix during impact, which allowed the CCFR honeycomb structure to have better low-velocity impact resistance, especially for repeated impacts with small energies. In contrast to the PLA honeycomb, the CAI test results showed that the CCFR honeycomb still retained good specific compression strength and specific energy absorption properties even after experiencing impacts. Furthermore, the continuous carbon fibre integrated into the CCFR honeycomb could be used as a sensor element to realize the in-situ structural health monitoring during impact and compression. The 3D-printed CCFR honeycomb structure, investigated in this research, demonstrates remarkable mechanical performance and self-sensing capabilities both during LVI and CAI tests, which highlights the vast potential of 3D-printed CCFR honeycomb for diverse applications.

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.

Effect of various factors and hygrothermal ageing environment on the low velocity impact response of fibre reinforced polymer composites- a comprehensive review

Effect of various factors and hygrothermal ageing environment on the low velocity impact response of fibre reinforced polymer composites- a comprehensive review

Numerical Study of Low-Velocity Impact Response of a Fiber Composite Honeycomb Sandwich Structure.

Engineering applications for honeycomb sandwich structures (HSS) are well recognized. Heterogeneous structures have been created using polyetheretherketone (PEEK) material, glass fiber-reinforced PEEK (GF-PEEK), and carbon fiber-reinforced PEEK (CF-PEEK) to further enhance the load-carrying capacity, stiffness, and impact resistance of HSS. In this study, we investigated the low-velocity impact response of HSS using numerical simulation. Our findings demonstrate that the choice of construction material significantly affects the impact resistance and structural stability of the HSS. We found that using fiber-reinforced PEEK significantly enhances the impact resistance of the overall structure, with GF-PEEK identified as the more appropriate face sheet material for the composite HSS based on a comparative study of load-displacement curves. Analysis of the plastic deformation of the honeycomb core, in combination with the stress and strain distribution of the composite HSS after low-velocity impact, indicates that CF-PEEK face sheets cause more noticeable damage to the core, resulting in evident plastic deformation. Additionally, we discovered that the use of fiber-reinforced materials effectively reduces deflection during low-velocity dynamic impact, particularly when both the face sheet and honeycomb core of the HSS are composed of the same fiber-reinforced PEEK material. These results provide valuable insights into the design and optimization of composite HSS for impact resistance applications.

Influence of fibre orientation, moisture absorption and repairing performance on the low-velocity impact response of woven flax/Elium® thermoplastic bio-composites

The importance of natural reinforced bio-composite materials with desirable properties such as high modulus-to-weight ratio, good impact resistance, and the ability to be easily repaired is crucial in the industry. A woven flax/Elium® thermoplastic bio-composite is manufactured to challenge these needs. Elium® is the only resin that permits the manufacture of large parts with thermoset-like processes, as Liquid Resin Infusion presented in that work. The paper highlights the influence of stacking fibre orientation, moisture absorption, and repair aptitude on its impact resistance. An instrumented drop tower was needed to conduct low-velocity impact tests at several energies and high-speed image coupled with microscopic observations was used to assess the damage evolution. The impact resistance was improved for the dry (0/90)6 orientation, but moisture absorption decreased its impact peak force by 20%. A three-point bending test was preferred to compression after impact for studying the residual properties after impact. The bio-composites with (±45)6 orientation showed higher impact residual performance than the (0/90)6 orientation, and corresponded to the reduction of maximum bending force by 20% than that of the reference. In addition, a thermo-compression process was applied to repair the impacted plates and conduct multiple impact/repair cycles which showed a significant recovery of stiffness and maximum impact force at 4J on (0/90)6 plates, highlighting their potential for repair in the automotive and marine industries.

Dynamic response of foam-filled X-type sandwich beam under low-velocity impact

The dynamic response of a fully clamped foam-filled X-type sandwich beam under low-velocity impact is studied analytically and numerically. The analytical model is developed for the dynamic response of the sandwich beam with foam-filled X-type core under low-velocity impact based on the yield criterion. The numerical calculations are carried out, and analytical results are in good agreement with numerical ones. The effects of face-sheet thickness, X-type folding plate thickness and foam strength on the impact resistance of the foam-filled X-type sandwich beam are discussed. It is shown that face-sheet thickness, X-type folding plate thickness, and foam strength have noticeable effects on the low-velocity impact response of the foam-filled X-type sandwich beam. The present analytical model can be used to predict the low-velocity impact of the foam-filled X-type sandwich beam.