American Institute of Aeronautics and Astronautics 1 A REVIEW OF SOFT BODY IMPACT ON COMPOSITE STRUCTURE Arafat I. Khan 1 and Rakesh K. Kapania 2 Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA Eric R. Johnson 3 Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA Recent progress in material modeling and numerical analysis related to soft body impact on fiber reinforced composite structure is presented. Material modeling of the composite includes continuum damage mechanics for intra-ply progressive failure and cohesive zone models for interface fracture. Soft body projectiles exhibit significant deformation on impact and flow over the structure spreading the load. A numerical model of the soft body that has been correlated to the test data is the smooth particle hydrodynamics method in conjunction with an equation of state. The composite material model and the soft body projectile model are implemented in explicit finite element software packages, which also contain contact algorithms and non-linear transient analysis capabilities. Nomenclature = strain vectors σ = stress vectors S = elastic compliance matrix E 1 , E 1 , E 12 = Young‟s moduli for composite ply G 12 = shear modulus for composite ply d 1 , d 2 , d 12 = damage parameters for the composite degradation model Y 1 , Y 2 , Y 12 = damage functions for composite degradation f 1 , f 2 , f 12 = damage evolution functions ε e = elastic strain ε p = plastic strain = „effective‟ shear stress R = isotropic hardening function p = accumulated effective plastic strain = yield stress σ 33 = tensile stress u 3 = displacement jump across the interface in cohesive zone model k 3 = the tensile stiffness u 30 , u 3m = displacements at the peak stress σ 33m = maximum peak stress for delamination model G IC = critical fracture energy C 0 , C 1 = material constants C 2, C 2 = material constants = ratio of current density and initial density ρ = current density ρ 0 = initial density v s = shock velocity 1 Graduate Research Assistant, Aerospace and Ocean Engineering, shuvo@vt.edu 2 Mitchell Professor, Aerospace and Ocean Engineering, rkapania@vt.edu , Associate Fellow, AIAA 3 Professor Emeritus, Aerospace and Ocean Engineering, erjohns4@vt.edu, Senior Member, AIAA 51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference<BR> 18th 12 - 15 April 2010, Orlando, Florida AIAA 2010-2865 Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.