Transformation field analysis of damage evolution in composite materials

Evolution of distributed damage in heterogeneous solids is modeled using the transformation field analysis method (Proc. Roy. Soc. Lond. A (1992) 437, 311) and selected models of interface debonding in fibrous or particulate composites. In this approach, stress changes caused by local debonding under increasing overall loads are represented by residual stresses generated by damage-equivalent eigenstrains that act together with the applied mechanical loading program and physically based local transformation strains on an undamaged elastic aggregate. Interaction of the actual and equivalent eigenstrains with the mechanical loads at any state of damage is described by certain transformation influence functions; this provides explicit expressions for the local stress averages and the damage-induced enhancement of the overall compliance at any current damage state. Damage rates are then derived from a prescribed probability distribution of interface strength and local potential energy released by debonding. Numerical simulations of damage evolution in a glass/elastomer composite indicate which of these two conditions controls the process at different reinforcement densities and overall stress states. In general, the energy released by a single particle at a given overall stress decreases with increasing reinforcement density, and in proportion to particle size. Therefore, dense reinforcement by small-diameter particles or fibers should enhance resistance to inclusion debonding in composite systems. (C) 2001 Elsevier Science Ltd. All rights reserved.