Aswani Kumar Bandaru

Effect of Projectile Geometry on the Deformation Behavior of Kevlar Composite Armors Under Ballistic Impact

A failure model based on the three-dimensional strains in a composite layer with improved progressive damage modeling has been implemented to predict the deformation behavior of composite armors subjected to ballistic impact. The present model comprises mainly of two parts. First, quadratic strain based failure criteria are presented to predict the initiation of failure modes. Second, the post damage softening behavior and degradation of the material stiffness is measured by damage evolution law. The model has been implemented within ABAQUS/Explicit as a user defined subroutine VUMAT. The validity of the model has been carried out by performing computational analysis of different composite armor materials such as Kevlar 29 and Kevlar 129 impacting with cylindrical-hemispherical nosed and 120° conical projectiles. It transpires that the predictions from the present model are in good agreement with the experimental and numerical observations available in the literature in terms of back face signature (BFS) for both the targets and projectiles. Further, the model has been implemented to study the effect of projectile geometry on the velocity time histories of the projectile, residual velocity and ballistic limit velocity. BFS values showed good agreement for conical projectile while for hemispherical projectile it is slightly low. The combination of Kevlar 129 armor and hemispherical projectile shows higher ballistic limit compared to that of the other combinations.

An experimental and numerical investigation on the low velocity impact response of thermoplastic hybrid composites

This paper presented an experimental and numerical investigation on the low velocity impact response of thermoplastic hybrid composites reinforced with Kevlar/basalt fabrics. Two hybrid and one Kevlar homogeneous composite laminates were manufactured with polypropylene as a resin. In the hybrid composites, one hybrid composite (H-1) was manufactured with alternate stacking of four layers of basalt and four layers of Kevlar and the second hybrid composite (H-2) was manufactured with four Kevlar layers on front face and four basalt layers on back face. Low velocity impact tests were performed using a drop-weight impact equipment at three different energies (25 J, 50 J and 75 J). Among the two hybrid composites H-1 hybrid composite exhibited 15.58–20.79% and 13.47–20.47% improvement in the peak force and energy absorption, respectively, than the H-2 hybrid composite. The peak force and energy absorption of Kevlar homogeneous composite was also improved by 10.07–14.37% and 5.38–11.29%, respectively, due to hybridization. A three dimensional (3D) dynamic finite element software, Abaqus/Explicit, was implemented to simulate the experimental results of low velocity impact tests. A user-defined material subroutine (VUMAT) based on Chang-Chang linear-orthotropic damage model was implemented into the finite element code. The predictions from numerical simulation were found to be in good agreement with the experimental results.