Impact Of Small Projectiles Research Articles

The investigation of deflection behavior in carbon/epoxy and glass/epoxy composite laminates under low-velocity impact with small projectiles

This study examined the impact behavior of carbon/epoxy and glass/epoxy composite laminates with 2, 4, and 6 mm thicknesses under low-velocity tests. The investigation involved subjecting the composite laminates under small-impact loads using spherical, cylindrical, and conical steel projectiles, each weighing 3 g. The impacts conducted at 29.5, 36.5, and 51 m/s velocities. This investigation modeled using finite element (FE) methods and analytical approaches. In the analytical method, the mass and spring model used for the impact of small projectiles. The research findings revealed that, in 2 mm thick carbon/epoxy composite laminates, the maximum deflection at the mid-point induced by a spherical projectile was 1.37 mm. This value exhibited a 48.91% and 19.13% increase compared to impacts with cylindrical and conical projectiles, respectively. Additionally, a comprehensive examination of delamination across all samples indicated the maximum delamination occurrence in glass/epoxy samples, showcasing lower impact resistance than carbon/epoxy laminates. Notably, with an increase in thickness, the delamination phenomenon in the samples exhibited a decreasing trend. In addition, the maximum value of delamination in the composite laminates were with spherical, conical, and cylindrical projectiles respectively, and also, there was an excellent convergence between FE and analytical results.

Effects of steel fiber and target thickness on the penetration resistance of UHPC under high velocity small projectile impact loading

Ultra high performance concrete (UHPC) with significant compressive strength and elastic modulus is expected to perform well under high–velocity impact loading. This paper introduces a study on the penetration resistance of UHPC based on variables including the thickness, fiber volume ratio, and striking velocity. The maximum striking velocity reaches approximately 1150 m/s. The results indicate that although the addition of steel fiber insignificantly improves the resistance, its effect on restraining the development of damage is non–negligible when the fiber volume ratio increases from 0.5% to 2%. The target thickness substantially influences the residual velocity and depth of penetration. Through computed tomography (CT) scanning, the damage can be divided into two parts: central damage (cratering, penetration tunnel, and scabbing) and interior cracks (radiate cracks, incomplete spalling cracks, and asymmetrical horn–shaped cracks). According to Forrestal's and the authors' previous models, satisfactory prediction results are obtained based on the suggested penetration resistance and modified cratering height.

The response of bio-inspired helicoidal laminates to small projectile impact

Helicoidal laminates mimicking the shells of mantis shrimp crustaceans have been found to be able to bear higher loads than conventional laminate configurations primarily through quasi-static or low-speed out-of-plane loads. However, mantis shrimps are known to withstand high speed impacts and there is a lack of such studies on helicoidal laminates. A study into the ballistic performance of helicoidal laminates was undertaken. The laminae of chitin fibers forming the shell were simulated by 3 different synthetic fiber reinforced laminates - carbon fiber reinforced epoxy, Kevlar fiber reinforced epoxy and polyethylene fiber laminates. Experimental results showed that helicoidal carbon-epoxy laminates with small inter-ply angles outperform cross-ply and quasi-isotropic laminates. However, helicoidal Kevlar-epoxy and polyethylene fiber laminates performed poorly relative to cross-ply laminates. Further investigations guided by experimental observations and numerical simulations show that matrix splitting is the dominant damage in helicoidal laminates with small inter-ply angles. The projectile perforates the laminate by crushing the fibers at the impact face of the laminate and then slipping through the matrix cracks developed at the back of the laminate attributed to matrix splitting. In contrast, fiber damage is the dominant mode of failure for cross-ply and quasi-isotropic laminates and helicoidal laminates with large angles. Such laminate configurations are therefore recommended for laminae reinforced by tough fibers. Conversely, bioinspired helicoidal lay-ups with small inter-ply angles are advantageous for brittle laminates. With the failure mechanism understood, an even higher ballistic limit is achieved for carbon-epoxy laminates through a mix of helicoidal and cross-ply configurations. The mixed-configuration laminate outperformed cross-ply and quasi-isotropic laminates by 32.6% and 86.6% respectively in terms of impact energy absorbed.

Finite Element Model of Functionally-Graded Cementitious Panel under Small Projectile Impact

This paper presents a three-dimensional finite element model for functionally-graded (FG) cementitious panel subjected to high-velocity small projectile impact using the commercial package, LS-DYNA. The FG-panel consists of PE-fibrous ferrocement as the top and bottom layers, sandwiching a thin layer of concrete with calcined bauxite aggregates and an infill of conventional mortar layer to form the remaining thickness. The impact responses of different panel configurations (by varying the thickness of individual layers) were simulated and the results compared well with experimental data for projectiles with striking velocities ranging from 300 m/s to 600 m/s. After model verification, an optimization study of the FG-panel configurations (thickness of composite layers) was performed with the aim of preventing perforation of the panel by a projectile with 600 m/s striking velocity. The impact response of a proposed FG-panel design was numerically simulated to evaluate its performance.

Development of functionally-graded cementitious panel against high-velocity small projectile impact

A functionally-graded (FG)-cementitious panel consisting of PE-fibrous ferrocement, calcined bauxite aggregates and conventional mortar was developed to resist high-velocity small projectile penetration. A total of 72 specimens measuring 200 mm by 200 mm by 100 mm were fabricated and subjected to ogive-nosed (Caliber Radius Head, CRH = 2.5) projectile impacts at velocities ranging from 300 m/s to 600 m/s. The results indicated that FG-panels have superior impact resistance compared to plain mortar targets in which all FG-panels remained intact, whereas the latter disintegrated into several pieces when the projectile velocity exceeded 300 m/s. The FG-panels also suffered minor front face damages with much smaller average crater diameters (<48 mm) compared to plain mortar targets (>100 mm). However, penetration depths in the FG-panels were slightly larger at impact velocity less than 400 m/s compared to the mortar panels due to the lower compressive strength of PE-fibrous ferrocement. At higher impact velocity, all penetration depths in FG-panels were smaller than those in plain mortar targets. The effects of thickness variation of each functional layer were also investigated and results showed that thickening the calcined bauxite aggregate layer was most effective in reducing the penetration depth for all impact velocities, but the average inner and outer crater diameters were slightly increased.

Behaviour of normal and steel fiber-reinforced concrete under impact of small projectiles

Steel fiber-reinforced concrete is currently used to provide massive armours against the impact of projectiles in sentry boxes, arms and powder depots, and other defence buildings. In this paper a set of trials intended to study the main factors affecting the impact of small projectiles on steel fiber concrete targets is described. The work is also oriented to obtain a design method for steel fiber concrete barriers against small projectiles and debris. This design method is different from the two main approximations to the problem followed thus far.

A Simple Catapult System for Studying the Small Projectile Impact Resistance of Various Glass Laminates

Abstract A catapult arrangement capable of propelling small granite chippings at velocities of between 4 and 20 ms-1 at laminated glass structures similar to those used in car windscreens has been designed and manufactured. The results from a series of studies utilizing this equipment are presented, with the overall aim of reducing the weight of these constructions with no loss in impact resistance. The impact resistance of the laminates has been shown to depend strongly on the thickness of the outer glass layer, while the inner glass layer is of secondary, and in most cases, minor relevance. Tests in which the composition and thickness of the interlayer have been varied have revealed that this layer is of no consequence in terms of the impact resistance of the structure as a whole. Chemical strengthening of the outer glass layer has been carried out, and no improvement in performance is observed due to the nature of the stone geometry. Finally, tests on bilayer systems have been carried out, and these results indicate a potential weight saving for no loss in impact performance.

A SPLIT-PLOT EXPERIMENT IN AN AUTOMOBILE WINDSHIELD FRACTURE RESISTANCE TEST

The resistance of laminated glass to small projectile impact is examined with a design of experiments technique. The analysis follows a split-plot design, but other closely related approaches such as repeated measure analysis and multivariate analysis are also discussed and compared.

Modelling deformation and damage characteristics of woven fabric under small projectile impact

Fabrics comprising highly oriented polymers possess high impact resistance and are often used in flexible armour applications. As these materials are viscoelastic, accurate modelling of their impact and perforation response requires formulation of constitutive equations representing such behaviour. This study incorporates viscoelasticity into the formulation of a model to analyse the impact of small spherical projectiles on plain-woven PPTA poly(p-phenylene-terephthalamide) fabric. The fabric is idealized as a network of viscoelastic fibre elements and a three-element viscoelastic constitutive model is used to represent polymer behaviour. Viscoelastic parameters are used to reflect intermolecular and intramolecular bond strengths as well as the static mechanical properties of fibres. Results of the theoretical analysis were compared with data from experimental tests on fabric specimens subjected to projectile impact ranging from 140 m/s to 420 m/s. Predictions of the threshold perforation velocity and energy absorbed by the fabric showed good agreement with experimental data. The proposed analysis is able to model deformation development and rupture of the fabric at the impact point. Fraying and unravelling of yarns are also accounted for. The study shows that a knowledge of static mechanical properties alone is insufficient and results in gross underestimation of impact resistance. An important parameter identified is the crimping of yarns. Yarns in woven fabric are not initially straightened out and hence part of the stretching in fabric is due to the straightening of yarns. The effect of crimping was found to be significant for high impact velocities.

A model for small-impact erosion applied to the lunar surface

A model for erosion of the lunar surface by impact of small projectiles is developed that provides an analytic representation of the change of crater shape as a function of time. The model is applied to the erosion of craters approximately 1 meter to 1 km in diameter. The lifetime of a crater in this size range, which is steadily eroded by impact, is approximately proportional to its radius. The model predicts the observed steady-state size frequency distribution of small lunar craters and the dependence of this distribution on the crater-production curve.

Design of SFRC barriers against impact of small arms projectiles

In this paper we present some results from a work developed in order to get some rational design method of SFRC against the impact of small projectiles. Firstly, we describe the way through which trials were done. Second, we present the principal results of this work. Based on it, a model is proposed to calculate both penetration depth of the projectile if it is not to perforate and residual velocity if it is to perforate, as well as perforation or scabbing threshold thicknesses. Owing to its physical basis and overall principles its application goes beyond -at least at the beginning- the field of steel fiber reinforced concrete. 1. Plates