Damage Tolerance Assessment of Laminated Composite Plates Subjected to Ballistic Impact

Abstract

Polymer matrix composite materials in laminated plate configurations are extensively used in a wide range of fields like defense, navy, aerospace, and automotive industries due to their low weight, high-specific strength, and tailorability. However, in these applications, impact damage tolerance of laminated composite structures is a constant source of concern over the years. Ballistic impact damage tolerance assessment is a concern in many fields, besides obvious application of protective armor where the primary design objective is that of preventing projectile penetration. Soft body armors made of composites are subjected to ballistic impact from projectiles where the structure has no time to respond and could result in localized damage. Analysis of composite structures under ballistic impact, which is a transient nonlinear dynamic phenomenon, requires nonlinear finite element analysis (NLFEA). LS-DYNA, a general purpose code based on finite element method with a wide range of material models, which uses explicit time integration technique for analyzing large deformation dynamic response of solids and structures, has proven to be relevant in this respect. This paper focuses on finite element modeling of impact on composite plates subjected to ballistic impact by a fragment simulating projectile (FSP) using LS-DYNA software. Finite element modeling is defined here as analyst’s choice of material models (constitutive equations and failure criteria), nonlinear finite elements, meshes, constraints, boundary conditions, analysis procedures, governing matrix equations, and their solution methods, specific pre- and post-processing options available in a chosen commercial FEA software for the intended analysis of candidate components and structures. The focus of this work is on the use of LS-DYNA software and prediction by analysis of: (1) Impact damage resistance (contact force-time history); (2) Impact response (displacement-time history, ply-by-ply strain history, ply-by-ply stresses in the material coordinates, and contour plots of failure index); (3) Impact damage propagation (ply-by-ply failure from first ply failure to last ply failure and delamination between plies); and (4) Impact damage tolerance (stiffness, strength, life without and with damage). Significant results like energy balance, contact force-time history, displacement-time plots, and damage zone shape and size are presented. Also, a study of the failure modes and effect of failure theories on ballistic impact response of a composite structure is presented.