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The paper presents the results of numerical simulation and experimental data on the high-speed penetration of the impactor into the obstacle. In the calculations, a discrete-element model has been used, based on the representation of the impactor and the target by a set of close packed interconnected particles. This class of models finds an increasingly wide application in the problems of high-speed interaction of bodies. In the previous works of the authors, the questions of application of the discrete-element model to the problem of the penetration of spherical impactors into massive targets were considered. On the basis of a comparative analysis of the data of computational and physical experiments, it was found out that for a wide class of high-speed penetration problems, a high accuracy of discrete-element modeling can be achieved using the two-parameter Lennard-Jones potential. The binding energy was identified as a function of the dynamic hardness of materials. It was shown that the use of this approach makes it possible to describe accurately the penetration process in the range of impactor velocities 500-2500 m/c. In this paper, we compare the results of discrete-element modeling with experimental data on penetration of high-strength targets of different thickness by steel impactors. The use of computational parallelization technologies on graphic processors in combination with 3D visualization and animation of the results makes it possible to obtain detailed spatio-temporal patterns of the penetration process and compare them with experimental data. A comparative analysis of the experimental and calculated data has shown a sufficiently high accuracy of discrete-element modeling for a wide range of target thicknesses: for thin targets pierced with preservation of the integrity of the deformed impactor, for targets of medium thickness, pierced with practically complete fragmentation of the impactor at the exit from the target, and for thick impenetrable targets.

This research work investigated the effects of SiO2 and ZrO2 nanoparticles type and content incorporated into an epoxy matrix on the high velocity impact behavior of carbon fiber reinforced aluminum laminates (CARALL). CARALL specimens consisted of a 0/90/90/0 stacking sequence of a carbon-epoxy composite containing 0, 1, 3, 5 and 7 wt% of each of nanoparticles sandwiched between two layers of aluminum 2024-T3. To observe the toughening effects of the nanoparticles on the fracture surface of the impacted CARALL, a typical field emission scanning electron microscope (FESEM) was employed. Impact energy absorption of CARALL was at most increased by 18 % and 12 % with the nanoparticles content of 5 wt% SiO2 and 3 wt% ZrO2, respectively. Overloading of the nanoparticles content up to 7 wt% resulted in the creation of nanoparticles aggregated sites associated with loss in the energy absorption capacity. FESEM fractography procedure also showed that the crack deflection and pinning were the most recognizable toughening mechanisms exhibited by nanoparticles. Overall, the controlled addition of SiO2/ZrO2 rigid nanoparticles to CARALL was found to be a promising method for improving the high velocity impact energy absorption of CARALL. [ABSTRACT FROM AUTHOR]

Composite materials are widely used in many civil and military applications because of their excellent mechanical properties. In military applications, composite materials are used to protect vehicles and aircraft and to manufacture shields for their ability to absorb and disperse impact energy. In this paper, used high velocity impact with a bullet (it mass of 8 g, diameter 9 mm and a semi-circular projectile head) with a specific velocity ranging from 210 - 365 m/s, to investigate the elastic deformation for composite plate structure with various composite laminated parameters effect. Where, studied the effect of the impact by using theoretically technique, in addition to, calculating the natural frequency for plates by using analytical and numerical techniques, and then, comparison the results obtained. In the theoretical part, problems were analysed into several categories, the first is the calculation of the elastic deformation in the composite materials samples which depends on several parameters such as the calculation of the natural frequency, the time and force contact, and elastic deformation. An equation for the calculation of elastic deformation was derived based on the classical theory of plates. Also, the natural frequency results calculated analytically by using classical theory of plates with drive the general equation of motion. Then, by using numerical technique calculating also the natural frequency of plates, and then, comparison the results obtained with analytical results obtained. When, the numerical technique include using for finite element technique to calculate the vibration behaviour for plate. Then, the comparison for results given a good agreement for analytical technique used with maximum error did not exceed about (1.23%). [ABSTRACT FROM AUTHOR]

The micromechanics based ceramic model developed by Deshpande and Evans (2008) is incorporated in a particle-based computational code in this article. Its performance in predicting response of ceramic target under high velocity impact is investigated through some benchmark experimental observations. For a better comprehension, the numerical predictions are also compared with that of obtained via the widely used phenomenological models by Johnson and Holmquist (JH1 and JH2). The efficiency and limitations of Deshpande-Evans model in capturing various failure mechanisms of ceramic are brought out to an extent. [ABSTRACT FROM AUTHOR]

Herein, the influence of bucky paper interleaves and dispersed MWCNT network on static and dynamic mechanical properties of Kevlar-epoxy composites, subjected to different loading conditions is investigated. Multiscale hybrid laminar Kevlar composites are prepared by vacuum impregnation followed by compression moulding technique. Subsequently, these hybrid composites are subjected to tensile, flexural, dynamic mechanical and low velocity impact and directly compared with basic Kevlar composite (KE) laminate. It is found that bucky paper interleaves along with dispersed MWCNT (KEBC) improve interlaminar and interfacial properties respectively. It is found that the maximum dynamic impact energy absorption and load carrying capacity of KEBC increase to 13.8 J and 2650 N respectively which shows an overall improvement of 31% over KE. These results are further confirmed by Charpy's impact test, in which maximum impact toughness reaches to 90.4 J/mm2, which is consistent with dynamic impact test results. After conducting various lab scale mechanical tests, ballistic test is also performed over KEBC and KE. It is found that, in case of KEBC, back face signature is reduced to 30% over KE, which confirms the collective effort of bucky paper interleaves and dispersed MWCNT in enhancing the energy absorption capability of hybrid laminar composite. Image 1 [ABSTRACT FROM AUTHOR]

Pre-loaded polymer composite structures subjected to high velocity impact have received little attention compared to the corresponding structure under static impact test. In fact, no report was found on such structures, which incorporate nanoparticles as a secondary reinforcement. The main objective of this research work is to assess the high-velocity impact response of polymer composite plates containing nanoclay under different pre-loads. E-glass woven roving and unsaturated polyester resin were used to prepare composite plates and 1.5 wt% nanoclay was introduced into the resin system. High velocity impact with full perforation as well as impact tests with rebound were conducted via a gas gun in a velocity range of 138–185 m/s. Three types of pre-loading were applied and compared with no pre-load condition, namely: uniaxial compression, uniaxial tension, and biaxial compression/tension hybrid pre-load. The results indicated significant better energy absorption performance by the nanoclay modified specimens under all pre-load conditions compared to the specimens without nanoclay. Results further showed that biaxial compression/tension and uniaxial compression pre-loads are more critical than tension pre-loads. Nanoclay reinforced composite plate showed greater damage extension compared to composite plates without nano reinforcement. Major failure modes identified include delamination, matrix cracking, and fiber breakage. • Pre-loaded hybrid nano composite structure under high velocity impact are investigated. • Preloading reduces ballistic performance and energy absorption capacity in composite panels. • Good energy absorption in Nano-clay containing panels under uniaxial tension and biaxial tension-compression preloads. [ABSTRACT FROM AUTHOR]

This paper introduces the initiation and evolution of interlaminar and intralaminar damage in the laminated composite plate under high-velocity impact with the finite element model. Damage in composite layers and delamination between layers are defined based on progressive damage model and cohesive zone modeling. Interlaminar and intralaminar damage initiation are predicted with Hashin criterion and traction-separation law and the damage evolution is predicted with reducing the value of stiffness based on fracture toughness energy that is available in ABAQUS. In this study, needed parameters for the finite element model such as fracture toughness energy are measured experimentally with some tests such as CT and DCB. The finite element model is valid with a velocity comparison of the impactor after impact in experimental impact test with 160J and the numerical simulation. The low percent difference between the experimental and numerical impact results is achieved and thus the needed parameters for simulation is extracted correctly. The present paper introduces a validated, accurate and low-cost finite element model with damage consideration and perforation of impactor for a laminated composite under the high-velocity impact that needed parameters could be measured experimentally. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a comparison of behavior and energy absorption of neat Kevlar fabric and polymer matrix composites under high velocity impact loading. Two types of matrices including rubber and thermoset (epoxy) matrices were used in order to study the effect of a hard and brittle matrix compared with the soft and flexible matrix on energy absorption of the composite. Moreover, two types of rubber matrix with high hardness (HH) and low hardness (LH) were used in this study to investigate the effect of rubber matrix formulation on impact resistance of composites. Ballistic impact tests were performed by firing a 10 mm hemispherical projectile onto neat fabric and composites in a velocity range of 30–150 m/s for two- and four-layer samples. Results show that the matrix affects the ballistic performance of composites significantly. Rubber matrix enhances the energy absorption of the fabric by keeping composite flexibility. Increase the number of layers for Kevlar/rubber composite results in better ballistic performance. On the contrary, the thermoset matrix leads to an inflexible composite that restricts the fabric deformation and has a negative effect on the fabric's ballistic performance. Finally, damage mechanisms were discussed in detail for each sample. [ABSTRACT FROM AUTHOR]

Abstract Fiber metal laminates (FMLs) have been widely used in many high-tech industries as protective structures because of their excellent impact resistance. The damage constitutive model that accurately characterizes the complex damage modes and failure processes of FMLs is the base to study the ballistic impact problems by numerical simulation. In this paper, a nonlinear finite element model based on continuum damage mechanics is established to investigate the damage modes and failure mechanisms of carbon fiber reinforced aluminum laminates (CRALLs) under high velocity impact. Johnson-Cook material model and a 3D rate-dependent constitutive model are applied to identify the in-plane damage in aluminum and fiber composite layers respectively; cohesive elements governed by bilinear traction-separation constitutive model are implemented to simulate the inter-laminar delamination induced by impact. The ballistic performance and damage characteristics of CRALLs under high velocity impact by projectiles with different shapes are studied in detail. The obtained numerical results correlate well with the available experimental data thus validates the proposed finite element model, which also provides an appropriate reference for numerical studies of high velocity impact issues in other FMLs. [ABSTRACT FROM AUTHOR]

Abstract This study presents the response of fiber reinforced composite material composed of woven Kevlar fabric impregnated with a colloidal shear thickening fluid (STF) under high velocity impact loading. The STF was made by dispersing silica nanoparticles at 15, 25, 35 and 45 wt.% loading in polyethylene glycol. The effects of silica nanoparticle loading on energy absorption and ballistic limit were studied experimentally. Rheological results revealed that shear thickening occurred at all four nanosilica loading and higher loading showing the higher shear thickening at lower shear rate. SEM images confirmed good dispersion of nanosilica particles in the suspension. The results of the pull out test show that by increasing nanosilica loading, the force required to pull the yarn out from the fabric impregnated by STF increases. Impact resistance performance of Kevlar fabric is significantly enhanced due to the presence of STF. Although high velocity impact results show that by increasing nanosilica loading, the energy absorption of composites increases, but in high loading of nanosilica, the effectiveness of STF decreases. For further investigation, the energy absorption at the ballistic limit was normalized by the areal density of the neat and impregnated fabrics to give the specific energy absorption (SEA). It is found that the SEA of 15 wt.% nanosilica loading is lower compared to the neat fabric. Also the highest SEA turn out in the case of 35 wt.% STF/Kevlar composites in which the SEA is 2.3 times larger than those of the neat fabric. [ABSTRACT FROM AUTHOR]

Abstract When designing light weight protective structures it is important to consider the threat from cased charges. In this research, a steel panel constructed using standard steelwork sections and a steel-concrete sandwich panel were loaded using a cased pipe charge containing 15 kg of TNT equivalent explosive. Central deflections and damage images were collected and were employed to validate finite element (FE) simulations. These were used to compare models using different stand-offs and two simplified smeared loading methods. The results showed that the influence of the localised damage was limited for the loading range considered. Highlights • Thin walled structures were tested with combined blast and fragment loadings. • The damage results were used to estimate the protective ability of the panels. • Numerical models were calibrated and used to assess the effects of the impacts. [ABSTRACT FROM AUTHOR]

• The ballistic performance of a cylindrical composite structure was investigated. • CSS with aramid HC core was impacted against conical and hemispherical projectiles. • The effects of FT, CT, and CS on ballistic resistance and EA were investigated. • Multi response optimization was carried out to identify the influential parameters. • FT was obtained as the most influential parameter, followed by CS and CT. This research explores the significance of structural modifications on the energy absorption and ballistic response of a cylindrical composite structure exposed to high velocity impact. The composite structure comprises an aramid honeycomb core supported by cylindrically shaped aluminum facesheets on both sides. Ballistic impact tests were performed by firing cylindrical projectiles, namely conical and hemispherical, using a pneumatic gun. Three-dimensional models of the composite structure with aluminum facesheets and an aramid honeycomb core were created using ABAQUS/Explicit. By utilizing numerical models, impact phenomena such as facesheet failure, core crushing, facesheet debonding, etc. were analyzed, which showed a high degree of similarity with a real impact scenario, thus validating the model. Furthermore, a parametric analysis was carried out using this model on different parameters affecting the composite structure. The study also examined the effect of these parameters on the ballistic responses of the cylindrical composite structure against both projectiles using a grey-based Taguchi analysis method. The investigation focused on multi-response optimization of the cylindrical composite structure's characteristics using Minitab software. The proposed grey-based Taguchi method proved effective in solving multi-response problems. [Display omitted] [ABSTRACT FROM AUTHOR]

• Functionally graded materials combine the hardness and lightness of ceramics with the toughness of metal. • Functionally graded materials are a promising candidate for armor material. • Damage mechanism of functionally graded plates under oblique ballistic impact is much more complex than normal impact. • The impact angle and material composition have a significant effect on damage and deformation of the functionally graded plates. The present study discusses experimental and numerical investigations on the dynamic response of functionally graded plates subjected to normal and oblique ballistic impact. Functionally graded plates were produced in a step-wise manner with powder metallurgy method using powder stacking-hot pressing technique. An experimental configuration was developed where projectiles impact functionally graded plates with three different compositions at impact angles of 0°, 15°, 30°, 45°, and 60°. Ballistic tests of functionally graded plates were carried out with a single-stage gas gun system using fragment simulating projectile (FSP) at velocities of approximately 610 m/s. The effect of the material composition and obliquity on damage and deformation of functionally graded plates was studied by varying the Al 6061 and SiC volumetric ratios to metal-rich (n = 0.1), linear (n = 1.0), and ceramic-rich (n = 10.0). Finite element analyses of functionally graded plates were performed with ANSYS Ls-Dyna explicit solver by employing the Mori Tanaka method to determine local material properties in the graded region and the TTO model to define elasto-plastic material behavior. The normal and oblique ballistic tests of functionally graded plates were compared with the values predicted from the finite element model in terms of damage, deformation, and fracture mechanisms. According to both numerical and experimental studies, the impact angle and material composition were found to be significant influences on damage and deformation of functionally graded plates. Given the complexity of the modeling of the ballistic impact events, the numerical models developed to predict the penetration depth and failure mechanism of plates in the ballistic impact tests showed a good agreement for n = 0.1 and n = 1.0 material compositions due to their metal-rich compositions. [ABSTRACT FROM AUTHOR]

А discrete element model is applied to the problem of a spherical projectile penetration into a massive obstacle. According to the model both indenter and obstacle are described by a set of densely packed particles. To model the interaction between the particles the two-parameter Lennard-Jones potential is used. Computer implementation of the model has been carried out using parallelism on GPUs, which resulted in high spatial - temporal resolution. Based on the comparison of the results of numerical simulation with experimental data the binding energy has been identified as a function of the dynamic hardness of materials. It is shown that the use of this approach allows to accurately describe the penetration process in the range of projectile velocities 500-2500 m/c.

Abstract High velocity impact on laminated composite panels is investigated by modeling, simulation, and experiments. Impact velocities of 100, 200, and 300 m/s are considered and normal as well as oblique impacts are studied. FEM simulations are conducted to design three different laminate configurations to achieve the cases of a reflecting, almost stucking, and fully perforating impactor, respectively. Within a domain where material nonlinearities are expected the shell-based ply-scale approach is used. Every ply is modeled by a layer of shell elements which are connected via cohesive zone elements. Both element types are assigned nonlinear constitutive laws to capture their mechanical behavior appropriately. Outside this domain, a single layer of composite shell elements is used. Corresponding laminated plates are produced and tested using a gas gun setup, where energy absorption and damage patterns are assessed. The comparison of simulations and experiments shows excellent agreement. The three cases are predicted well, and also the damage patterns and the energy absorptions match very well. [ABSTRACT FROM AUTHOR]

Abstract In order to obtain the effect of hygrothermal aging on the high speed impact resistance of carbon fiber reinforced composites (CFRP), ballistic impact tests using flat blades projectile were conducted on the T700/TDE-85 laminates subjected to artificial accelerated hygrothermal aging (70 °C, RH95%) for different durations. Short beam shear tests were conducted on the aged specimens to evaluate the interfacial properties degradation. The effect of hygrothermal aging on the energy absorption and ballistic limit of composites were discussed. It is shown that the moisture absorption rate of the composites is in agreement with Fick law, with an equilibrium moisture absorption rate of 0.74% at 1369 h. The interlaminar shear strength (ILSS) descends rapidly with aging time and the retention rate of interlaminar shear strength was 50.6% after 2000 h. The ballistic limit and the critical energy absorption of the composites declined notably with the increase of aging time. Due to the weakened fiber/matrix interface, the delamination failure area in rhombic shape is of increasing severity with aging time. The matrix cracking and fiber/matrix interface debond due to long-term exposure to hygrothermal environment reduce the high velocity impact resistance of the composites. [ABSTRACT FROM AUTHOR]

The effects of adding surface modified graphene nanoplatelets (GNPs) in various weight percentages (0, 0.1, 0.2, 0.3, 0.4, 0.5 with respect to matrix) on the high velocity impact response of basalt fibers/epoxy composites were evaluated. High speed mechanical stirrer and ultrasonic waves were used for the dispersion of GNPs in the epoxy matrix, and hand layup method was utilized for the fabrication of the composite samples. High velocity impact testing was performed using a conical projectile. The results demonstrated that the maximum improvement in the impact limit velocity and energy absorption occurred in the 0.3 wt.% GNPs nanocomposite, i.e., 11 and 23 %, respectively. Also, the electron microscopy studies revealed that the addition of GNPs contributed in improving the impact properties by influencing the matrix and thus enhancing the interfacial characteristics between the basalt fibers and the matrix. [ABSTRACT FROM AUTHOR]

Abstract High velocity transverse impact on reinforced composites is a matter of interest in the automotive, aeronautical and biomedical sectors. Most existing studies have addressed this problem by single isolated impacts; however, this work deals with the distinction between single, sequential and simultaneous impacts on composite structures. This paper proposes an experimental methodology to study the mechanical behaviour of materials under single and multi-impact loadings. The overall objective is to investigate the mechanical response of short carbon fibre reinforced PEEK when is subjected to single and multiple high velocity impacts. Experimental tests are conducted covering impact velocities from 90 m/s to 470 m/s. Energy absorption, damage extension and failure mechanisms are compared to assess additive and cumulative effects in high velocity impact scenarios. Experimental results show that the specific deformation and fracture mechanisms observed during multi-hitting events change with impact velocity. Compared to the behaviour of unreinforced thermoplastics, short fibre reinforced composites present significant limitations at velocities close to the ballistic limit, but multi-hit capability is observed at high impact velocity when the damage is mainly local. As key conclusion, the ballistic limit obtained in single impact test cannot be extrapolated to sequential and simultaneous tests. Multi-impact tests, especially close to the ballistic limit, are necessary to guarantee the structural integrity of composite structures in realistic impact scenarios. [ABSTRACT FROM AUTHOR]

Abstract In this experimental study, high velocity impact behavior of honeycomb sandwich structures with Al6061/B 4 C FGM face plates subjected to 0.30 caliber fragment simulating projectile impact was investigated via a single-stage gas gun. The material composition of the FGM face plates was represented according to a power-law variation through the plate thickness. The specimens were produced for six types of face plates, Al6061 and five different FGM face plates from metal-rich to ceramic-rich composition. Impact test results of the specimens were evaluated in terms of their damage and deformation mechanisms. The test results stated that the material composition variation of the FGM face plates was a highly influential parameter for damage modes, energy absorbing capacity, and impact resistance of the sandwich structure, and the honeycomb core contributed to the energy absorbing capacity of the sandwich structure with the plastic buckling of the cell walls and lateral crushing deformations. [ABSTRACT FROM AUTHOR]

The Hydrodynamic Ram (HRAM) phenomenon occurs when an object with a high-kinetic energy impacts against a fluid-filled structure, which could induce important damages. An attenuation technique would be of great interest for structures which could be subjected to impact. In this work, honeycomb panels are used to fill the entire space inside the structure in such a way that they are able to alleviate the loading onto it. Experimental tests were carried out varying aluminium honeycomb cells orientation, to determine the configuration that mitigates more efficiently the effects of HRAM comparing the results with a non-protected structure. The experimental tests were analysed using a high speed video camera, strain gauges, residual displacement of the structure walls and the deformation of the honeycomb panels. It is shown that for all the configurations, the honeycomb is able to reduce the plastic deformation of the structure. The honeycomb allows to reduce the cavity expansion in the fluid, which is the most dangerous phenomenon in the studied cases. The best configuration is able to diminish up to 54% the residual expanded volume in the structure walls, and hence considerably attenuating the HRAM effect on the structure. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An analytical modeling is developed in a range of elastic waves propagation to investigate the nonlinear behavior of thin laminated composite plate. These plates reinforced by nanoparticles under high-velocity impact. Four crucial regions are considered: fracture region, nonlinear deformation region, local movement region and delamination region. In addition, based on a new deformation function, new equations are developed for assessing the normal and shear strains and computing the energy absorbed in different regions. Results of the present study show a good agreement with the available experimental data of other researchers at velocities beyond the ballistic limit velocity (i.e. V>V B.L ≈ 120 m/s). [ABSTRACT FROM AUTHOR]

Composite structures due to their low strain to failure are regarded as a brittle material and are susceptible to possible impact damage during manufacture, maintenance and in use. This paper describes the influence of tension, compression and hybrid preload on E-glass/polyester composite plates under high velocity impact loading in a velocity range of 185 to 235 m/s. Six layered, E-glass plain weave woven roving [0/90] 6 composite panels were made by hand layup method. An innovative preloading apparatus, which is patented with number IRI-83450 was developed to apply the preloading in uniaxial and biaxial directions. This device was used simultaneously with a gas gun to conduct high velocity impact tests. A spherical hard body projectile was used in the impact tests. Uniaxial tension, uniaxial compression and biaxial tension and compression preload were applied to each specimen. To assess the strain rate sensitivity of the material concern under different preloading, three different impact velocities were used. Result showed, the ballistic resistance of the samples with the different preloading condition decreased compared to no preload case. Less variation was observed in exit velocities in the upper impact velocity range test (235 m/s) conducted for all boundary conditions used. A significant increase in the rate of change of residual velocity was observed for the impact velocity of 185.3 m/s compared with that of higher impact velocities tested. Delamination and fiber fracture constituted the major fracture modes followed by matrix fracture. [ABSTRACT FROM AUTHOR]

Ballistic resistance has become towards researchers' attention especially those in enforcement industry. In the ballistic resistance, researchers are keen to determine the lowest velocity of projectile that able to perforate a target. From result obtained, researchers can propose modification to enhance the survival of enforcement personnel. For an example, armor shield which is employed by enforcement personnel during gun fight. The main objective of this paper was to present the preliminary result of ballistic resistance of aluminium plate that will be used as a reference in the experiment works later. Future works will involve aluminium laminated with z-composite. In this study, the target was aluminium plate with thickness of 3 mm and fragment simulating projectile (FSP) acted as the projectile. The FSP was launched from gas gun which was located 2 meters from the aluminium plate. The velocity of FSP was varied by changing the charge weight. The experiment was carried-out at Science and Technology Research Institute for Defence (STRIDE), Batu Arang. From the experiment conducted, it was found the ballistic limit was equal to 257.7 m/s. Furthermore, there were two main modes of failure observed which were non-perforation and successful perforation. For non-perforation, the mode of failure was crater with and without FSP embedded into the plate. Meanwhile for the successful perforation, the mode of failure was a hole along with petals. [ABSTRACT FROM AUTHOR]

Three-dimensional angle-interlock woven composites (3DAWCs) are usually employed as exposed components in aerospace and other high-tech areas due to their superior impact resistance. In this work, the experimental characterization and numerical modeling are combined together to study the ballistic performance and damage behavior of 3DAWCs under high velocity impact (HVI). The initial-residual velocity relation is examined by ballistic impact test and the penetration process is recorded by high-speed camera. A nonlinear finite element (FE) model based on a multi-scale modeling framework is established to simulate the ballistic impact response and damage behavior of 3DAWCs. The proposed FE model is verified by comparing the predicted initial-residual velocity curve and penetration propagation with the experimental data. Parameter analysis is conducted to address the influences of projectile diameter and impact angle on the impact performance of 3DAWCs and the corresponding damage mechanisms are revealed in detail. The present work provides a transferable approach for studying the HVI problems of other textile composite structures. • Experimental characterization and numerical modeling are combined to study the ballistic impact behavior of 3DAWCs. • A multi-scale modeling is performed to simulate the ballistic impact response and damage behavior of 3DAWCs. • The effects of projectile diameter and impact angle on the ballistic impact response of 3DAWCs are investigated. • The developed multi-scale modeling framework provides a reference for HVI problems of 3D textile composite structures. [ABSTRACT FROM AUTHOR]

The impact response of an E-glass fiber reinforced epoxy/Nomex® honeycomb core sandwich was investigated both experimentally and numerically at increasing velocities through concentrated quasi-static indentation force (CQIF), low velocity impact (LVI) and high velocity impact (HVI) tests. The composite face sheets and core were modelled using MAT_162 and MAT_026 homogenized material model in LS-DYNA, respectively. The experimental and numerical LVI test forces corresponding to core crushing and face sheet penetration were shown to be higher than those of the CQIF tests and increased as the impactor velocity increased. The increase of the impact forces at increasing velocities was largely ascribed to the inertia and the strain rate sensitive fracture strength of the composite sheets. The core shearing was detected in the CQIF and LVI tests both experimentally and numerically. It was also detected in the HVI tests at the velocities less than 20 m s−1. The deformation in the HVI tests at and above ∼ 29.4 m s−1 was highly localized in the impact area with no core shearing and a large delamination damage area at the front face sheet. The force enhancement due to the micro-inertia of the core deformation was shown to be not significant at the studied velocities. [ABSTRACT FROM AUTHOR]

This paper investigates the energy absorption and deformation characteristics of sandwich structures with auxetic tetrachiral core under high velocity projectile impact. The finite element model of the structure is developed using the Johnson-Cook material model and is used to study the effects of projectile impacts for velocities between 150 and 450 m/s. The FE model is validated using in-house experiments on 3D printed PLA sandwich with tetrachiral core under hemispherical projectile impact and also using experimental data reported in the literature. Further, a semi-analytical model is developed to estimate the residual velocities and energy absorption of sandwich structure under blunt projectile impact, which shows good agreement with the FE results with an error of less than 8%. Finally, the performance of the sandwich structure with tetrachiral cores is studied under projectile impact for velocities ranging from 150 to 350 m/s and compared with sandwich structures with re-entrant and double arrowhead cores. The results show that for velocities above the ballistic limit, the energy absorbed by the facesheets, and core are nearly constant and is greatest for blunt projectile impact, followed by hemispherical, ogive, and conical geometries. Furthermore, sandwich structures with auxetic cores exhibit better energy absorption characteristics compared to those with hexagonal honeycomb cores. [ABSTRACT FROM AUTHOR]

Since woven fabrics have uniqe characteristrics such as light weight, flexibility, high strength, etc. and they are also capable to be improved for mechanical properties by nano thechnology, it is expectal to gain more efficient composite using intrinsic properties of the ceramic nanoparticles and proper coating method. The uniqe properties of the nanoparticles such as high elastic modulus, high strength to weight ratio etc. as well as participating in defeat mechanisms agains external loadings, can be of the factors reinforcing the textiles. Al2O3-13%TiO2 coatings were deposited on Kevlar Fabric substrates from nanostructured powders using atmospheric plasma spraying (APS). A complete characterization of the feedstock confirmed its nanostructured nature. Coating microstructures and phase compositions were characterized using SEM, and XRD techniques. The microstructure comprised two clearly differentiated regions. One region, completely fused, consisted mainly of nanometer-sized grains of α-Al2O3 with dissolved Ti+4. The other region, partly fused, retained the microstructure of the starting powder and was principally made up of nanometer -sized grains of γ-Al2O3, as confirmed by FESEM. Coatings were in average slightly lower than the values for nanostructured coating. The results of tensile testing on kevlar fabrics before and after coating showed that APS could improve tensile strength up to 60%. High velocity impact test (V50) performed on coated fabrics well indicated that their ballistic limit experienced a significant increase. In addition, the results of V50 showed revealed that APS can decrease final weight of new composite panel compared to plain polyetylen panel with identical protection level. [ABSTRACT FROM AUTHOR]

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 E BL , a new parameter proposed in this work. E BL is the energy absorbed by the target at the ballistic limit normalized by the contact area. [ABSTRACT FROM AUTHOR]

Bullet proof vests have been designed for decades to provide protection against different type of threats like small arms ammunition. Although pure fabric is being used in most of bullet proof vests but back face signature is very high in plain fabric. This back face signature or blunt can causes severe damage to body parts resulting in internal bleeding and sometimes even causing death. So it is also an important factor to be considered while designing a bullet proof vest. A lot of different methods are being used in literature to upsurge the impact response of Kevlar Fiber Reinforced Polymer (KFRP) composite like addition of Nano-clay, change of fiber orientation, use of toughened epoxy etc. In this research, effect of different matrix combinations on blunt trauma and energy absorbed by KFRP laminates are studied. KFRP composite samples are prepared with epoxy and different percentages of rubber + epoxy, and are experimentally tested against 9mm Full Metal Jacketed (FMJ) bullet. The ballistic impact behavior and back face signature measurement of Kevlar/epoxy composite and Kevlar/epoxy with different percentages of rubber are compared with that of pure fabric. Results from the experiments have shown positive effect, of adding rubber in matrix, in terms of energy absorption (i.e. penetration), reduction in back face signature and damage mechanism for ballistic impact event. During experiment it is found that failure of primary yarn, elastic deformation of secondary yarn, delamination and matrix cracking are the main energy absorption mechanisms. The results have shown that the laminates with a combination of rubber and epoxy give optimum results i.e. better impact resistance with lesser blunt trauma or back signature. Among these samples the sample with 12.5% rubber has best results. [ABSTRACT FROM AUTHOR]

The effects of projectile diameter and impact velocity on fragment size distribution were investigated by striking aluminum alloy 6061-T6 targets with aluminum alloy 2017-T4 spheres of 1.6 to 7.0 mm in diameter at impact velocities ranging from 2 to 7 km/s. Two-stage light-gas guns from the Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency and Nagoya Institute of Technology were used for the experiments. After the impact experiments, fragments were collected from the test chamber, and the fragment lengths were measured. Scaling laws for size distribution of fragments were discussed. The fragment length was directly proportional to projectile diameter. When the horizontal axis of the fragment length distribution was divided by the projectile diameter, the normalized fragment length distribution was proportional to the impact velocity raised to the power 1.5. The empirical formula with respect to the fragment length distribution could be expressed using the projectile diameter and impact velocity. The proposed scaling law with respect to fragment length could be applied to projected areas of fragments and fragment masses and the validity of the scaling law was confirmed. The fragment length was directly proportional to crater size such as crater diameter and crater depth. The horizontal axis of the fragment length distribution could be normalized by each crater depth or crater diameter. [ABSTRACT FROM AUTHOR]

Soft body armour panels have been developed by tuning the structure of 3D woven orthogonal aramid fabrics and reinforcing them with shear thickening fluid (STF). Five 3D woven orthogonal aramid fabric structures were prepared by changing the ratio of stuffer (X direction) to binder (Z direction) yarns and also by changing the relative position of the latter. Two types of ballistic evaluations, namely energy absorption against low velocity (165 ± 10 m s −1 ) bullets and back face signature (BFS) against high velocity (430 ± 10 m s −1 ) bullets were carried out for neat and STF impregnated 3D fabrics and their panels. STF impregnation improved impact energy absorption by 3D woven aramid fabrics. Increasing the ratio of stuffer to binder yarns was found to be beneficial in terms of impact energy absorption and resistance against bullet penetration. STF impregnated 3D fabrics having 4:1 stuffer to binder ratio performed the best in ballistic evaluations. Synergistic effect of 3D woven fabric structure and reinforcement of STF was found to be the key for successful design of soft body armour. [ABSTRACT FROM AUTHOR]

In this paper, multi-wall carbon nanotube (MWNT) added carbon fiber reinforced plastics (CFRP) composites are suggested as solutions to improve the impact energy absorbing capability of CFRP for spacecraft application because it was proven that the resistance against LEO environment and the quasi-static material properties of CFRP can be improved by adding MWNT in previous papers. To verify the effect of MWNT on the impact energy absorbing capability of composite materials, normal CFRP and MWNT-reinforced CFRP were prepared and tested by using a two-stage light gas gun that can accelerate an aluminum ball of a diameter of 5.56 mm to 1 km/s. And the applicability of MWNT against hypervelocity impact of space debris was studied. In addition, accelerated ground simulation experiments were performed for each material model to simulate the aging of composite materials to verify the effect of LEO environmental aging on impact absorbing capability of composites. For the aging experiment, the impact specimens were simultaneously exposed to high vacuum, atomic oxygen, ultra violet light, and thermal cycling. After being exposed to simulated LEO environment, high velocity impact tests were performed for each material. As a result, MWNT did not have a significant improvement on the impact energy absorbing capability of CFRP under high velocity impact, even though the quasi static material properties are improved by adding MWNT. This is caused by the early generation of fiber breakages on the impact surface before enough generation of progressive failure which is one of the impact energy absorbing mechanism. Similarly, MWNT has less effect on the impact energy absorbing capability of CFRP under LEO environment. [ABSTRACT FROM PUBLISHER]

In this research, the finite element method has been utilized for investigation of the progressive damage in composite laminates. Governing equations on progressive damage in three dimensional stress and strain field have been expressed based on Hashin's onset of damage and Matzenmiller's progression of failure. The damage equations were coded to make a material model in LS-Dyna. This model could simulate various damage modes such as fiber breakage due to tension or compression, failure due to inplane shear, crushing and delamination. High velocity impact on woven composite laminates has been analyzed using this material model subroutine. Damage pattern, ballistic limit velocity and growth of damage parameter in different failure modes have been investigated. Also, the occurrence of multimode damage at an element and degradation of the elastic modulus of the composite material and its softening were studied. In addition, the effect of impact on damage growth at near field and far field of the impact zone, as well as complete or partial damage of the composite laminate have been investigated. Based on outcomes, the number of plies plies is the plural of ply of composite laminate and its thickness has an important role on the manner of the results. Also, for a damaged element, change of failure mode by growth of the damage parameters was observed. [ABSTRACT FROM AUTHOR]

In this paper, a novel hybrid composite shield to protect space structures from hypervelocity impact of micrometeoroid and space debris is proposed. The finite-element model of the proposed shield was constructed and finite-element analysis was conducted to approximate the energy absorption rate. Before the final model analysis, analysis of each component including the aluminum plate (front plate), PMMA plate (rear plate), and intermediate layer of fabric was performed, verifying the finite-element model of each component. The material properties used in the analysis were predicted material property values for high strain rates. The analysis results showed that, other than the fabric, the energy absorption rate of each component was in agreement. Afterwards, the finite-element model of the hybrid composite shield was constructed, where it was analyzed for the constrained and unconstrained fabric boundary condition cases. Through the finite-element analysis, the fiber pullout mechanism was realized for the hybrid shield with free boundary inserted fabric, and it was observed that this mechanism led to energy absorption increase. [ABSTRACT FROM PUBLISHER]

The aim of this work is to investigate the effect of basalt fibre hybridization on carbon/epoxy laminates when subjected to high velocity impacts. In this regard, interply hybrid specimens with four different stacking sequences (sandwich-like and intercalated structures) are tested and compared to non-hybrid reference laminates made of either only carbon or only basalt layers. The response to high velocity impact tests is assessed through the evaluation of the impact and residual velocities of the projectile and the ballistic limit, calculated using experimental data, is compared with the results given by an analytical model, showing a good agreement. The damage in composite laminates is investigated by destructive (optical microscopy) and non-destructive (ultrasonic phased array) techniques. As a result of basalt hybridization, the ballistic limits of all sandwich configurations are enhanced if compared to those of carbon laminates. Therefore the observed decrease of static mechanical properties of hybrid composites is largely compensated by improved response to impact. Advantages also come in terms of cost saving, since the basalt fibre is far less expensive than the carbon one. [ABSTRACT FROM AUTHOR]

The aim of this article is the construction of a multiphase hyperelastic model. The Eulerian formulation of the hyperelasticity represents a system of 14 conservative partial differential equations submitted to stationary differential constraints. This model is constructed with an elegant approach where the specific energy is given in separable form. The system admits 14 eigenvalues with 7 characteristic eigenfields. The associated Riemann problem is not easy to solve because of the presence of 7 waves. The shear waves are very diffusive when dealing with the full system. In this paper, we use a splitting approach to solve the whole system using 3 sub-systems. This method reduces the diffusion of the shear waves while allowing to use a classical approximate Riemann solver. The multiphase model is obtained by adapting the discrete equations method. This approach involves an additional equation governing the evolution of a phase function relative to the presence of a phase in a cell. The system is integrated over a multiphase volume control. Finally, each phase admits its own equations system composed of three sub-systems. One and three dimensional test cases are presented. [ABSTRACT FROM AUTHOR]