Pseudoplasticity of Fibrous Composite Materials: Inelastic Response of Laminates with Interfacial Decohesion

Abstract

After fabrication or in service, certain metal and ceramic matrix laminates may exhibit extensive decohesion, such as debonding and sliding at fiber-matrix interfaces. The evolution of the decohesion process, as well as its effect on overall response and on redistribution of local stress and deformation fields, is analyzed here with a modification of the transformation field analysis method (Dvorak 1992). A finite element analysis of a unit cell model of a fibrous ply is used to obtain the decohesion-induced changes in the potential energy, needed in local fracture criteria. Changes in the local stresses and overall strains are found and converted into effective phase eigenstrains that produce identical average fields in a perfectly bonded ply. Finally, transformation strain analysis of a laminated plate is developed for derivation of governing equations for incremental evaluation of the local fields along a given overall loading path. Applications indicate that the decohesion process may generate overall response similar to that of an elastic-plastic laminate.