Damage Analysis and Prevention in Composite Materials

Abstract

A new model for incremental analysis of distributed damage evolution in heterogeneous solids is developed with the Transformation Field Analysis. Stress changes caused by local debonding under increasing overall loads are described by a selected model of imperfectly bonded inhomogeneity and represented by equivalent eigenstrains that act together with the applied loads and prescribed local transformation strains on an undamaged aggregate. Interaction between the still bonded and partially debonded phases at any damage state is described by transformation influence functions. Damage rates are derived from the local fields, in terms of a prescribed probability distribution of interface strength and local energy released by debonding. An incremental procedure is outlined that predicts the extent of damage and its effect on local and overall response under variable loads. Also, potential applications of fiber prestress in damage control and prevention in laminated structures are illustrated by two examples. One shows how prestress release can expand the tensile damage-free region of symmetric laminates. Another derives the fiber prestress magnitudes needed to eliminate free edge stress concentrations caused in any laminated plate by cooling from the processing temperature.