High Velocity Impact Response Research Articles

Effect of the polymer interlayer on the high-velocity soft impact response of laminated glass plates

The choice of the polymer interlayer is a key consideration for laminated aircraft windshields. Such windshields often employ chemically strengthened glasses and are required to withstand impact by birds, hail-stones and other foreign bodies. In the present study, windshields employing three different polymer interlayer materials were investigated under high-velocity impact by a soft projectile: Thermoplastic Polyurethane (TPU), Polyvinyl Butyral (PVB) and Ionoplast interlayer-SentryGlas® Plus (SGP). Parameters such as the polymer interlayer type and thickness, multi-layering the interlayer and the sensitivity of the behaviour of the windshield to the environmental temperature were studied. The performance was assessed through a series of laboratory-scale impact experiments (using a bird-substitute material) and modelled via finite element simulations (using a smoothed particle hydrodynamics approach). The experimental and numerical results were found to be in good agreement for the three polymer interlayers investigated. The polymer interlayer type was found to have the most significant effect on both the deformation and the failure of the laminated glass windows at room temperature, i.e. 25 °C. However, the influence of the polymer interlayer type became less pronounced at lower temperatures. The novel modelling that has been developed assists in the choice of the best polymer interlayer, including the multi-layering of interlayers, for complex windshield designs.

High-velocity micro-particle impact on gelatin and synthetic hydrogel.

The high-velocity impact response of gelatin and synthetic hydrogel samples is investigated using a laser-based microballistic platform for launching and imaging supersonic micro-particles. The micro-particles are monitored during impact and penetration into the gels using a high-speed multi-frame camera that can record up to 16 images with nanosecond time resolution. The trajectories are compared with a Poncelet model for particle penetration, demonstrating good agreement between experiments and the model for impact in gelatin. The model is further validated on a synthetic hydrogel and the applicability of the results is discussed. We find the strength resistance parameter in the Poncelet model to be two orders of magnitude higher than in macroscopic experiments at comparable impact velocities. The results open prospects for testing high-rate behavior of soft materials on the microscale and for guiding the design of drug delivery methods using accelerated microparticles.

Molecular influence in the glass/polymer interface design: The role of segmental dynamics

Recent observations of the high-velocity impact response in poly (urethane urea), PUU, elastomers has inspired a new inquiry on whether enabling molecular mechanisms could benefit dynamic impedance optimization at the interface of a glass/polymer bilayer, particularly at the moment of impulse interaction. In this work, we investigate the molecular influence on dynamic impedance using microballistic measurements on two bulk elastomers, a PUU and a polyurea, PU. Upon impact at strain rates ∼108/s, PUU exhibits a moderate improvement in resistance against penetration than PU, that is more pronounced at higher speeds. The variation in dynamic stiffening corroborates well with the corresponding segmental dynamics data determined via broadband dielectric relaxation. Meanwhile, we calculate the shock impedance from the shock velocity data derived from the respective shock Hugoniot to discern the efficacy of dynamic impedance optimization between PUU and glass. New insight on molecular attributes will guide glass/polymer interface designs.

High velocity impact response of 3D hybrid woven composites

The aim of this work is to develop an efficient numerical model which can predict the behavior of 3D hybrid woven composites under high velocity impact by utilizing the inbuilt constitutive and damage models within the finite element software. To predict the constitutive and damage behavior of composites during the high velocity impact process, a combination of cohesive contact and continuum shell elements is proposed in finite element (FE) model. Delamination behavior is characterized by introducing the cohesive contact between the two adjacent laminas using the traction separation law, while damage, induced during the impact process in each single layer of composite laminate, is depicted by continuum shell elements with Hashin failure criterion. Connector elements containing the failure behavior are introduced into the model to represent the z-yarns of the 3d woven composite. The proposed FE model reveals good capturing of damage phenomenon during the impact process and indicates good agreement with experimental results, making it a valuable tool for characterizing the impact response of 3D hybrid woven composites under high velocity impacts.

Effect of shape memory alloy wires on high-velocity impact response of basalt fiber metal laminates

Fiber metal laminates are commonly used materials in industrial applications due to low density and excellent mechanical properties such as impact resistance. In this study, the effect of shape memory alloy wires on the impact properties of fiber metal laminates is evaluated and discussed. The volume fraction of wires and the pre-strain of wires were selected as the variables of the experiments. The samples were fabricated using hand lay-up method and their behavior was evaluated under high-velocity impact test. Based on the results, a significant change in the amount of absorbed energy was obtained using embedded wires. However, with increasing the volume fraction of wires, the absorbed energy decreases due to the discontinuity in mechanical properties of the specimens. On the other hand, applying pre-strain leads to residual stresses in samples. The observed residual stress in specimens with four embedded wires and 2% pre-strain level shows the most absorbed energy.

High velocity impact response of carbon nanotubes-reinforced composite sandwich panels

Effect of adding carboxyl-modified multi-walled carbon nanotubes (COOH-MWCNTs) on the high velocity impact of sandwich panels with plywood core and two different facesheets, E-glass/epoxy and E-glass/ nylon 6, was investigated in this study. Facesheets were prepared with and without COOH-MWCNTs. Three different weight percentages of 0.3, 0.5, and 1 wt% of COOH-MWCNTs were used to reinforce epoxy and nylon 6 polymers. The sandwich panels’ estimated ballistic limit ( Vbl) and impact energy absorbed ( Eab) were determined by subjecting them to impact velocities in their ballistic limit range and above by conical nose projectile. It was found that the sandwich panels containing E-glass/ epoxy facesheets exhibited more energy absorption than those containing E-glass/nylon 6 facesheets. Moreover, the high velocity impact response of sandwich panels improved with the increase of COOH-MWCNT content. Besides, the damage area for different types of materials studied is presented, and it is observed that at a given impact velocity, the damage size on the rear facesheet of target around the point of impact decreases on addition of COOH-MWCNTs.

An experimental investigation into the high velocity impact responses of S2-glass/SC15 epoxy composite panels with a gas gun

The single-stage gas gun testing methodology was investigated. A thermodynamics based method was used to estimate the required pressures for a targeted velocity. The transmitted impact force was measured with four load cells installed behind the testing frame. The out-of-plane deformation was measured with a projection grating profilometry method using a high speed camera. The velocity of the projectile was determined from the high speed video footage. The improved gas gun experiment was used to investigate the high velocity impact behavior of a S2-glass/SC15 epoxy composite. The ballistic limit was found to be 338 m/s and 406 m/s for the 6-ply and 10-ply composite panels, respectively. It was observed that the failure modes of the composite panels evolved with the impact velocity. The area of damage and failure first increased and then became localized. The panels absorbed the same or even a slightly higher amount of energy beyond the ballistic limit before damage localization. The ballistic protection capability of the S2-glass composite was compared with other materials in terms of EBL, a new parameter proposed in this work. EBL is the energy absorbed by the target at the ballistic limit normalized by the contact area.

Dynamic responses of metal sandwich beams under high velocity impact considering time inhomogeneity of core deformation

The objective of this paper is to establish a yielding criterion for a sandwich beam by considering the time inhomogeneity of foam core deformation, which results in the time-varied neutral surface and cross-sectional area. Taking into account of the bending and axial stretching, a unified dynamic yielding criterion for metallic sandwich beams considering the mass redistribution along with the core compression is established. A membrane factor is proposed and an analytical solution for the large deflection of the beam under high velocity impact is given. Different from the traditional yielding surface, when the core is partially densified, the yielding surface is asymmetric. Comparison of analytical solutions with numerical ones reveals that the present model improves the prediction accuracy of high-velocity impact responses of fully clamped sandwich beams. The present method can also be degenerated to predict the low velocity/energy impact responses of sandwich beams.

Mechanical and morphological study of polymer composite plates having different fiber surface treatments with particular response to high velocity projectile impact

This study investigates morphological and mechanical behaviors of polymer composite plates reinforced with surface modified glass fiber woven roving with special interest in high velocity impact response. Four types of surface modification were applied to the glass fiber surface, namely: virgin fabric (silane coupling agent removed), silane-treated (as received fabric), corona-treated virgin fabric and silane- plus corona-treated fabric. Hand layup technique was adopted to make composite plates with [0/90, ±452, 0/90] layup using unsaturated polyester resin as matrix. Mechanical testing methods, such as tensile and bending loading as well as low velocity Izod impact and high velocity impact tests in velocities of 88.5, 108.3 and 144 m/s were conducted. The results showed that, although in lower part of high velocity impact rates, i.e., 88.5 m/s, the panels with fiber fabric treatment of silane plus corona revealed significant increase in ballistic resistance, but in general, it was found that the order of optimum performance for E-glass fiber woven roving surface modification methods are: silane, silane plus corona treatment, virgin fabric and sole corona treatment, respectively. The results further revealed that at impact velocities of 108.3 and 144 m/s, the energy absorptions for the samples with silane treatment are 7.9 and 6.6% higher compared to the samples with silane plus corona discharge treatment (S + C) samples, respectively. Damage assessment revealed higher damage extension in the samples with fiber having silane plus corona discharge treatment. Morphological studies on surface roughness were conducted by SEM analysis. The results correlated well with mechanical and impact results in those samples with higher surface roughness showed better mechanical performance and that silane treatment was the dominant factor in performance.

Investigations on Steel Fibre Reinforced Cementitious Composite Panels under High Velocity Impact of Short Projectiles

Response of steel fibre reinforced cementitious composite (SFRCC) panels subjected to high velocity impact of short projectiles have great significance in designing protective structures. Numerical investigation carried out to determine the high velocity impact responses of SFRCC (300 mm square) panels is presented. In order to model the high velocity impact behaviour of SFRCC in the post peak region, the constitutive model of Riedel, Hiermaier and Thoma (RHT) is used with suitable modification in damage parameters. The numerical studies presented in this paper are validated using the experimental investigations carried out by the authors. The influences of steel fibrevolumes (0, 2, 4, 6, 8, and 10%) and thickness of panels (50, 60, 75, 100 mm), on depth of penetration (DOP) and crater dimensions is also investigated. Based on the numerical simulations, the important phenomenon like scabbing and perforation in the SFRCC panels are predicted for the chosen in-service ammunition (7.62 mm calibre) and munitions (AK - 47 rifle).

High velocity impact responses of sandwich panels with metal fibre laminate skins and aluminium foam core

In this paper, high velocity impact responses of newly designed sandwich panels with aluminium (AL) foam core and metal fibre laminate (FML) skins, which are comprised of aluminium sheets and plain woven E glass fibre composite plies are investigated. Gas gun impact tests were conducted to investigate the high velocity impact response of the panels subjected to the impact from a steel ball bearing at an impact velocity of around 210m/s. The effect of the thickness of the foam core and FML skin on the impact resistance of the panels is also investigated via experimental study. A finite element model is developed for effective numerical modelling of the impact behaviour of the sandwich panels using the commercially finite element software ANSYS LS-DYNA for more extensive study of the impact response of the sandwich panels. The simplified Johnson Cook material model, the composite damage material model based on the Chang-Chang criteria, and the crushable foam material model are used to model the aluminium sheets, composite plies and the AL foam respectively. Three types of contact algorithms, i.e. the erosion contact type, the tie-break contact type and the general 3D contact type are employed to define the various contacts during the impact and to model the delamination between the FML layers and debonding between the FML skin and the AL foam. The finite element model is validated by comparing the simulated impact behaviour to that from experimental for a sandwich panel subjected to high speed impact and demonstrated to be effective and accurate. The effect of the shape of projectile and impact angle on the impact behaviour of the sandwich panels is studied using the developed finite element model. The research findings are summarized and concluded finally.

Effects of static preloads on the high velocity impact response of composite plates

The paper discusses a high velocity impact scenario where representative fuselage composite plates are statically preloaded and then impacted with a blunt impactor at velocities in the range 70–105m/s. Compression and tension preloads that represent design limit load were considered as well as lower preloads that a structure would carry more frequently. Gas gun impact tests were performed to generate a validation database for comparison with results from numerical simulation. A modelling methodology to simulate preloads and transient impact events was documented. The numerical model captures intra- and inter-ply damage by using layers of shell elements connected with cohesive interface layers. Both test and simulation results indicate an influence of static preloads on the impact damage response. The numerical model was especially used to better understand the interaction between preloads and dynamic impact loads which are complex especially for impact on buckled plates.

Improvement in impact resistance performance of glass/epoxy composite through carbon nanotubes and silica nanoparticles

Experimental studies are presented on the high velocity impact behavior of nanomaterial dispersed resin viz laminates made using E-glass fabric with epoxy resin. The nanomaterials used are silica nanoparticles and carboxyl functionalized multi-walled carbon nanotube (COOH-MWCNT) for polymer matrix composites. The composites' ballistic limit ( Vbl) and impact energy absorbed ( Eab) were determined by subjecting the material to impact loading of 85, 100, and 112 m/s by conical nose projectile. It was found that the high velocity impact response of epoxy composites improved when a nanomaterial was used as reinforcement. COOH-MWCNTs reinforced composites exhibited better energy absorption than silica nanoparticles composites. Moreover, the damage pattern for different types of materials studied is presented. It is observed that the damage size on the target around the point of impact decreases on addition of nanoparticles especially COOH-MWCNTs. Quantitative data are presented for high velocity impact behavior of the seven types of specimens studied.

Dynamic deformation characteristics of zirconium diboride–silicon carbide under multi-axial confinement

Multiaxial quasi-static and dynamic compression experiments were performed on zirconium diboride-5wt% silicon carbide (ZrB2-5wt%SiC) ceramic composite processed via spark plasma sintering technique. Cylindrical ZrB2–SiC specimens were confined using thick walled metal sleeves to generate various levels of confinement pressure on the lateral surface and then subjected to axial loads under quasi-static and dynamic conditions. Postmortem analysis revealed formation of a macroscopic shear plane in the recovered specimens and slip bands within ZrB2 grains. Compressive strengths of up to 5.6 GPa and 9.8 GPa, respectively, were reached under quasi-static and dynamic strain rates. To capture the strain rate dependent and pressure dependent response the Johnson–Holmquist (JH-2) model was used and relevant parameters were determined for future high velocity impact or shock response simulations utilizing the experimental data generated from low and high strain rate confined compression tests. A comparison of JH-2 model constants for ZrB2–SiC along with other structural ceramics revealed that pressure alone plays a deterministic role in defining the constitutive response of all brittle ceramics including ZrB2–SiC.

Investigation of high velocity impact of cylindrical projectile on sandwich panels with fiber–metal laminates skins and polyurethane core

In this study, the high velocity impact response of sandwich specimens with FML skins and polyurethane foam was investigated by experimental and numerical approaches. Impact tests were performed using a helium gas gun to identify deformation mechanisms and to check accuracy of finite element model. The 3D finite element code, LS-DYNA was used to model impact of cylindrical projectile with clamped boundary condition. Parametric studies were carried out incorporating different core densities, initial velocities of projectile and layerʼs stacking sequence. The results show the facesheets have major contribution on energy absorption of the sandwich specimens. Also, increasing core density does not significantly change absorbing energy in comparison with the effects of other parameters. Comparison of different layer sequences of skins indicated that these panels have benefits of both composite sandwiches and metal sandwiches, simultaneously. Examining damaged specimens demonstrated the cracks in front and back facesheet develop in different patterns. Circumferential crack was made in front facesheet, and radial crack was made in back facesheet.

Impact response and damage evolution of triaxial braided carbon/epoxy composites. Part I: Ballistic impact testing

To investigate the high-velocity impact response and damage evolution of the triaxial braided composite fan case, a series of ballistic impact tests using blade-like projectiles were conducted. Cylindrical projectiles of the same cross-section perimeter were also employed to identify the influence of projectile geometry. In addition, satin woven composites were tested for comparison with respect to failure modes and damage shape. Experimental results indicate that the main failure modes for the two different fiber reinforcement architectures are similar, that is, fiber shear failure and matrix crush failure in the impact surface and fiber tensile failure, fiber pull-out, matrix cracking, and delamination in the exit surface. The damage area in the exit surface is diamond-shaped for satin woven composites while rounded or elliptic for triaxial braided composites according to projectile geometry. The triaxial braided composites have an improved ballistic resistance and higher ballistic limit than satin woven composites. Based on damage area and failure modes observed from experiments, ballistic behavior was predicted using an analytical model, which proves to be accurate enough.

The Behaviour of Fibre-Metal Laminates under High Velocity Impact Loading with Different Stacking Sequences of Al Alloy

The high velocity impact response of composite laminated plates has been experimentally investigated using a nitrogen gas gun. Tests were undertaken on fibre-metal laminate (FML) structures based on Kevlar-29 fiber/epoxy-Alumina resin with different stacking sequences of 6061-T6 Al plates. Impact testing was conducted using a cylindrical shape of 7.62 mm diameter steel projectile at 400m/s velocity, which was investigated to achieve complete perforation of the target. The numerical parametric study of ballistic impacts caused by similar conditions in experimental work is undertaken to predict the ballistic limit velocity, energy absorbed by the target, and comparisons between simulations by using ANSYS AUTODYN 3D v.12.1 software and experimental work to study the effects of the shape of the projectile with different (4, 8, 12, 16 and 20mm) thicknesses on the ballistic limit velocity. While only one thickness was used with 24mm of back stacking sequence, it was not penetrated. The sequence of the Al plate position (front, middle and back) inside laminate plates of the composite specimen was also studied. The Al back stacking sequence plate for the overall results obtained was the optimum structure to resist the impact loading. The simulation results obtained of the residual velocity hereby are in good agreement with the experimental results with an average error of 1.8%. The energy absorption was obtained with 7.3% and 2.7% of the back to front and back to middle of the Al stacking sequence respectively. Hence, the back Al stacking sequence is considered the optimum position for resisting the impact loading. The data showed that these novel sandwich structures exhibit excellent energy-absorbing characteristics under high-velocity impact loading conditions. Hence, it is considered suitable for aerospace applications.

Multi-walled carbon nanotube-filled polypropylene nanocomposites: high velocity impact response and mechanical properties

Polymer nanocomposites containing 0.75, 1.0 and 1.5 wt% of multi-walled carbon nanotubes (MWNTs) in a polypropylene (PP) matrix were studied in relation to their low and high velocity impact performances. PP nanocomposites reinforced MWNTs were prepared via melt compounding in an internal mixer followed by injection molding. Transmission electron microscopy analysis confirmed well dispersed 1 wt% MWNT in the polymer nanocomposites. The same analysis showed agglomeration and cluster formation in 1.5 wt% MWNT specimens. Results showed increase in Izod impact strength in nanocomposites containing 1 wt% MWNT, which attained the highest value (with 33.4 % increment). A single stage gas gun was used to carry out high velocity impact test in velocity range of 20–150 m/s using hard steel hemispherical tip projectile of 11.34 g weight and 8.1 mm diameter. Results showed better ballistic limit velocity (the average of highest impact velocity causing perforation but unable to go through and lowest impact velocities with no residual velocity recording) and energy absorption for specimens, each containing 1 wt% MWNT, showing the highest value (with 100 % increment), compared with neat PP. Considerable increases were observed in tensile and flexural strengths and modulus for the MWNT-containing specimens as compared with neat PP.

The Influence of impact on Composite Armour System Kevlar-29/polyester-Al2O3

An experimental investigation of high velocity impact responses of composite laminated plates using a helium gas gun has been presented in this paper. The aim of this study was to develop the novel composite structure that meets the specific requirements of ballistic resistance which used for body protections, vehicles and other applications. Thus the high velocity impact tests were performed on composite Kevlar-29 fiber/polyester resin with alumina powder (Al2O3). The impact test was conducted by using a cylindrical steel projectile of 7.62mm diameter at a velocity range of 160-400 m/s. The results (shown in this work) are in terms of varying plate thickness and the amount of energy absorbed by the laminated plates meanwhile we obtained that the 12mm thickness of composite plate suitable for impact loading up to 200m/s impact velocity. Therefore this composite structure (it is used to reduce the amount of Kevlar) considered most economical armoure products. We used the ANSYS AUTODYN 3D- v.12 software for our simulations. The results have been obtained a4.1% maximum errors with experimental work of energy absorption.

The high-velocity impact response of thermoplastic–matrix fibre–metal laminates

The high-velocity impact response of fibre metal laminates based on a woven polypropylene fibre reinforced polypropylene, termed a self-reinforced polypropylene, and a glass reinforced polypropylene has been investigated. Two types of aluminium alloy were considered, these being the 2024-O and 2024-T3 alloys. Tests on these composite–metal hybrids were undertaken using a gas gun over a wide range of incident impact energies. In this study, attention focused specifically on the perforation threshold. Following impact, the fracture mechanisms in the two types of fibre metal laminates were elucidated by sectioning and polishing samples through the point of impact and also by measuring the residual deformation of the hybrid plates. Cross-sections of the failed samples highlighted significant plasticity within the volume of these hybrid materials, indicating that considerable energy had been absorbed in plastically deforming the aluminium and composite plies. The impact resistances of the various laminates were compared by determining their specific perforation energies. Here, it was shown that fibre metal laminates based on the glass reinforced polypropylene composite offer a slightly higher perforation resistance than the self-reinforced polypropylene fibre metal laminates. Also, the fibre metal laminates based on the stronger 2024-T3 alloy out-performed their 2024-O counterparts. Finally, the perforation resistances of the fibre metal laminates were predicted using the previously reported Reid–Wen impact perforation model. Good agreement was observed between this impact model and the measured experimental data.