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In this study, we describe the development of a shell model-based macro-scale approach for a stainless steel 304 wire mesh using Hill's yield criterion and elasto-plastic material behaviors. The constants for orthotropic elastic-material response and the parameters for non-linear behavior were determined from experimental tests. For validation and comparison, the results obtained using this macro-scale model were compared with the experimental data obtained from drop-tower impact tests and the simulation results from a meso-scale model. The comparison highlighted that the macro-scale model of the wire mesh is more suitable for large-size simulations. [ABSTRACT FROM AUTHOR]

• Key developments in dynamic testing techniques of yarns and fabrics are summarized. • Gripping fibers effectively is essential in dynamic tensile tests. • The morphology of a yarn affects its transverse deformation behavior. • Polymer spray coating is a method for improving fabric penetration resistance. • Current challenges and future research directions are discussed. This mini review provides a succinct overview of dynamic mechanical tests for woven fabrics and ballistic fibers, which are widely used for penetration-resistant applications. Considering the structural hierarchy of woven fabrics, this work highlights recent studies at different scales, encompassing uniaxial tensile tests and transverse impact tests of yarns, yarn pull-out tests from fabrics, and transverse impact tests of fabrics. The dynamic characterization techniques employed in these tests are discussed, along with the associated challenges. This paper serves as a quick guide for those seeking to gain insights into the dynamic behavior of woven fabrics. [ABSTRACT FROM AUTHOR]

• UHMWPE yarns are highly sensitive to strain rate at low rates of deformation. • There is a threshold for strain rate above which strain rate effect is negligible. • Plain weave fabrics have better impact performance than satin weave fabrics. • Spherical projectile penetrates UHMWPE fabrics by a 'wedge-through' mechanism. • A mesoscopic modelling approach of woven fabrics at the yarn level is proposed. A comprehensive study on the impact behaviour of UHMWPE woven fabrics is presented in this paper, which consists of four parts: geometric measurement of fabric parameters, tensile testing of constituent yarns, impact testing of fabrics, and numerical modelling of fabrics subjected to impact loading. Two fabric materials, i.e. a plain weave fabric made of SpectraⓇ 1000 fibres and a 4-harness satin weave fabric made of DyneemaⓇ SK75 fibres, were examined. Firstly, the geometric features of fabrics, such as yarn cross-sections and weave profiles, were characterised via microscopic analysis. Then the tensile properties of single yarns at different strain rates were measured, and results showed that UHMWPE yarns are highly sensitive to strain rate at very low loading rates. Tensile strength as well as longitudinal modulus showed a noticeable increase, whereas failure strain and toughness decreased with the increase of strain rate. However, these properties remained nearly constant in the strain rate range from 0.33 to 400 s−1. Furthermore, projectile impact tests were conducted on single-ply and multi-ply fabric targets under different impact velocities. The energy absorption characteristics, perforation mechanism, and yarn pull-out behaviour were analysed. Finally, finite element models of the fabrics were developed based on the measured geometric parameters and tensile properties of constituent yarns. The models were able to accurately simulate the impact response of the fabrics studied. The insights gained from this investigation will facilitate the effective utilisation of UHMWPE fabrics in armour and other protective applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Woven wire mesh is a metallic fabric outperforming traditional metal sheets in air circulation, weight saving, impact resistance, etc. In this study, the dynamic mechanical response of steel wire mesh subjected to low-velocity impact loading was investigated using both experimental and numerical methods. An instrumented drop-weight impact facility was used for experimental impact tests, with the effects of clamping wire direction, impact energy, impactor's mass and size being considered. The extents of damage to the wire mesh specimens under different loading conditions were evaluated after impact tests. Three types of contact force vs. displacement curves corresponding to the plastic deformation, wire breakage, and perforation of wire mesh were identified. Weft wires were found to be stronger and stiffer than warp wires because they could resist higher peak forces and experienced smaller maximum displacements under the same impact energies. The experimental results revealed that the peak contact force increased with impact energy until wire breakage occurred, after which the peak force remained almost unchanged. With the increase of impactor mass, wire mesh specimens experienced severer damage due to the inertia effect and strain rate effect. Impactor size had a significant influence on the dynamic response of wire mesh; a great increase in peak contact force was found when using a larger impactor tip. Moreover, a mesoscale finite element model was developed to analyse the propagation of stress and the evolution of dynamic failure in wire mesh during impact. The simulation results showed that more than 80% of the impactor's kinetic energy was absorbed through the deformation and failure of wire mesh, while the frictional energy dissipation accounted for about 10% of impact energy. • Three types of contact force vs. displacement curves of wire mesh were identified. • Weft wires could resist higher force corresponding to wire breakage than warp ones. • Wire mesh material behaved in a membrane stretching mode under low-velocity impact. • Impact-induced stress propagated in an orthotropic manner in wire mesh. • More than 80% of impact energy was absorbed as the internal energy of wire mesh. [ABSTRACT FROM AUTHOR]

• The critical shear rate decreases with the increase in temperature. • The formation of shear bands evolving into cracks on the free surface of the STF is observed at 0 °C. • The response time for effective energy absorption is faster at lower temperatures and under higher impact velocities. • A one-dimensional model is presented to predict the response time for energy absorption. Shear thickening fluid (STF) material is a suspension with a certain amount of nano- or micro-particles dispersed into a liquid medium whose viscosity increases with the rate of shear strain. Due to its exceptional rate-dependent property, STF has been regarded as a promising energy absorption material with potential application in soft body-armour. This study examines the rheological, impact resistance and energy absorption characteristics of an STF with concentrated polymer submicron particles under various temperatures. The rheological testing was conducted using a rotational rheometer with a temperature-control hood at shear rates measured from 0.01 s−1. The studies reveal that the shear thickening behaviour of the STF is temperature-dependent and the critical shear rate for the onset of shear thickening decreases with the reduction of temperature. In particular, shear thickening behaviour of the STF at 0 °C was observed with the formation of shear bands evolving into cracks on the free surface of the STF. Low-velocity impact tests were conducted using a drop-weight tower with a temperature-control chamber. The study shows that the impact resistance of the STF increases with the decrease in temperature. In particular, the impact resistance shows an early response time when the impact resistance slowly picks up, corresponding to mechanisms of jamming-associated "solidification" and propagation of front of the "solidified" region. A simple one-dimensional model is also adopted to comprehend the response time for effective energy absorption of the STF addressing the mechanisms, and the general agreement of the predicted response time with that from the experiments demonstrates the effectiveness of the model. [ABSTRACT FROM AUTHOR]

Abstract The dynamic responses of sandwich panels with homogeneous and stepwise graded aluminium foam cores subjected to impact loadings were investigated via experimentation and finite element simulation in this paper. The low-velocity impact tests were conducted using a drop-weight impact facility at four different velocities, the results of which were compared in terms of force-displacement response, energy absorption and damage status. It was found that the density gradient of graded foam cores had a marked influence on the deformation and failure behaviour of front facesheets. Moreover, different facesheet materials were experimented with a homogeneous foam core, and the results showed that the impact response of a sandwich panel was dominated by its front facesheet. The front facesheets having same materials deformed and failed in the same manner irrespective of the back facesheet materials. The results of finite element analysis indicated that the critical impact energy required to cause failure to the front facesheet increased with the density of first core layer. Besides, the impact performance of sandwich panels could be improved efficiently by increasing the front-to-back thickness ratio while the total thickness of both facesheets remained the same. Graphical abstract Unlabelled Image Highlights • The density gradient of graded foam cores markedly influenced the deformation and failure behaviour of front facesheet. • The critical impact energy required to cause failure to the front facesheet increased with the density of first core layer. • The perforation resistance of entire sandwich panels was affected slightly by the core density gradient. • The impact performance of sandwich panels was improved by increasing the thickness ratio of front to back facesheet. [ABSTRACT FROM AUTHOR]

This paper presents a combined experimental and numerical study on the low-velocity impact behavior of honeycomb-core sandwich panels with different structural parameters, including facesheet thickness, core height, honeycomb cell size, and cell wall thickness. Impact tests were conducted at four different energies using a drop-weight impact facility, and the deformation and damage characteristics of the tested sandwich panels were analyzed by microscopic X-ray computed tomography. The experimental results revealed two distinct failure modes of sandwich panels: namely mode A, with localized damage in both facesheets and core, which is dominated by indentation; and mode B, which is characterized by global bending deflection of the facesheets and overall core crushing. It was found that a sandwich panel with thin facesheets and a high-density honeycomb core (e.g. with a small cell size and/or a thick cell wall) tended to fail in mode A, but core height did not influence the failure mechanism notably. Furthermore, finite element modeling was carried out to gain further understanding of the effects of these structural parameters. The perforation resistance and energy absorption capacity were significantly enhanced with increasing facesheet thickness. Whereas reducing the cell size and/or thickening the cell wall resulted in lower perforation resistance. When the total thickness of facesheets remained a constant, the impact behavior of the sandwich structure could be optimized by controlling the thickness ratio of the front to back facesheets. Finally, cost efficiency analysis was performed to achieve a rational design of the sandwich structure considering both the impact performance and cost. • Two failure modes of sandwich panels are discovered under low-velocity impact. • Failure mode depends on facesheet thickness, cell size, and cell wall thickness. • Core height does not influence the failure mechanism notably. • The density of honeycomb core shows a negative effect on perforation resistance. • A cost efficiency analysis is proposed to balance the impact performance and cost. [ABSTRACT FROM AUTHOR]

The existing damage constitutive models for a composite lamina under impact loading have mainly considered four failure modes: longitudinal fiber failure in tension and compression, matrix failure in tension and compression along the transverse direction. However, when subjected to an impact load in the out-of-plane direction, through-thickness compression failure may also occur in laminates. Therefore, the present paper has established a damage constitutive model considering through-thickness compression failure and has compared it to those constitutive models without such consideration to see the improvement in the impact response analysis and to discuss the necessity of including through-thickness compression damage in the simulation. To this end, impact testing was conducted on manufactured composite panels, and the results were used to validate the finite element simulation of composite laminates under impact. The results showed that the constitutive model with the compression failure mode in the thickness direction had higher accuracy in predicting the impact force, displacement, damage, and energy absorption of laminates. The predicted results by the developed constitutive model showed that through-thickness compression damage indeed occurred in the laminates during the impact process, and it was mainly concentrated in the layers near the impact side. In the layers near the rear side, the tension damage of longitudinal fiber and matrix mainly initiated and developed in the annular region around the impact center on the laminates. [ABSTRACT FROM AUTHOR]

Ballistic impact tests were conducted on polymer-coated multi-layer fabric targets using 0.357 SIG projectiles. The effect of fatigue loading on the yarn pull-out force of coated Twaron fabrics was studied for the first time. A validated mesoscale numerical modelling approach was developed to simulate the ballistic impact. The elastomeric coating significantly improved impact resistance. The coating is stable in a wide range of ambient temperatures and performs well upon being subjected to fatigue. A coated target having 6.6% less areal density and 20% less thickness than its neat counterpart has shown similar ballistic limit velocity. • The number of rubber coatings positively affected the peak pull-out force (PPF). • PPF was 25%–30% higher in dynamic tests than in quasi-static tests. • PPF exhibited no sensitivity to ambient temperature up to 60 °C. • Application of a fatigue loading reduced the PPF by 14% • Coated target exhibited a 7% weight reduction but performed equally to neat target. [ABSTRACT FROM AUTHOR]

• PBSL showed significantly higher compression strength than other bio-composite materials. • Specimens with height/width ratio more than 2 produced consistent results under quasi-static testing. • Height of specimen showed approximately negligible effect on material responses under drop-weight. • Better dynamic deformability was observed for specimen impacted perpendicular to the fibre. • The compression response of PBSL was deemed to be strain-rate sensitive. This paper investigates the compression behaviour of 42 Parallel Bamboo Strand Lumber (PBSL) specimens under quasi-static and drop-weight impact loading. 25 mm × 25 mm square specimens with varying heights and fibre orientations were tested to investigate compression and impact resistance of PBSL. Quasi-static results indicated a distinct 5-stage failure pattern for the complete quasi-static loading history with a 45° failure plane in all specimens when the compression load was applied parallel to the fibres. Specimen height did not affect the ultimate load carrying capacities but showed considerable influence on the initial stiffness as well as the post-ultimate loading regime. Experimental results showed that the deformation ratio and the energy absorption ratio for longer specimens were not affected by fibre orientations. Low-velocity drop-weight impacts were conducted under 25.4 J and 101.5 J energy levels. Specimen height did not play any significant factor during impact testing. The initial impact level dominated the maximum deformation and dynamic energy absorption observed in specimens that failed showing a 4-stage deform procedure. Although the deformation patterns between fibre orientations were distinctly different, similar energy absorption capacities were obtained regardless of specimen height. Comparison of experimental evidences obtained from quasi-static and drop-weight impact tests clearly showed that the compression response of PBSL is strain-rate sensitive. [ABSTRACT FROM AUTHOR]