Shivdayal Patel

Reliability Analysis of a Composite Plate under Low-Velocity Impact using the Gaussian Response Surface Method

A 3-D explicit dynamic finite element analysis is performed to determine the contact force and displacement between the impactor and the target. The uncertainties associated with the properties of the composite material, loading condition, and assessment of critical stresses affect the failure limit state to a greater extent. The Gaussian response surface method is used to predict the probability of failure. It is found that the system probability of failure is influenced more by delamination than the failure due to matrix cracking. Shear strength (T12) and Youngs modulus (E1 and E3) are the most sensitive parameters to influence the composite plate reliability.

Probabilistic Finite-Element Analysis of S2-Glass Epoxy Composite Beams for Damage Initiation Due to High-Velocity Impact

The safety predictions of composite armors require a probabilistic analysis to take into consideration scatters in the material properties and initial velocity. Damage initiation laws are used to account for matrix and fiber failure during high-velocity impact. A three-dimensional (3D) stochastic finite-element analysis of laminated composite plates under impact is performed to determine the probability of failure (Pf). The objective is to achieve the safest design of lightweight composite through the most efficient ply arrangement of S2 glass epoxy. Realistic damage initiation models are implemented. The Pf is obtained through the Gaussian process response surface method (GPRSM). The antisymmetric cross-ply arrangement is found to be the safest based on maximum stress and Yen and Hashin criteria simultaneously. Sensitivity analysis is performed to achieve the target reliability. This article is available in the ASME Digital Collection at http://dx.doi.org/10.1115/1.4033575.

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.

Stochastic Finite Element Analysis of Composite Body Armor

The ballistic impact response of a composite target is an important investigation to assess its reliability for applications to light weight body and vehicle armors. The progressive damage model is developed and implemented in the finite element (FE) code ABAQUS as a user-defined subroutine (VUMAT). A numerical result is obtained using deterministic progressive damage model are validated against existing experimental study in literature. Stochastic finite element analysis (SFEA) is used to study the fiber failure in tension; fiber crushing and in-plane shear failure modes due to ballistic impact. The random variation in material properties and initial velocities are used to determining statistics of stress in the lamina. These are compared to the random strengths in the limit state function and P f surface is obtained by using Gaussian process response surface method (GPRSM). The comparison of P f obtained from Monte Carlo simulation (MCS) and GPRSM. MCS computationally 10 times more expensive in comparison to GPRSM. System P f based on a fault tree analysis is determined to cross and angle ply arrangement in symmetric and anti-symmetric laminates. The P f of symmetric cross ply laminate arrangement for simply supported composite beams are found to be minimum.