Techniques for characterizing damage zones in composite materials

Abstract

Experimental methods for determining the existence of a work potential, useful in characterizing material response even in the presence of significant damage, are developed and described. The underlying fracture theory and motivation for the development is briefly discussed. The theory involving the work potential and the existence and use of a damage parameter is reviewed, as is the basic composite laminate theory and underlying constitutive formulation. An experimental program which addresses these factors through the biaxial loading of composite tubes is presented. The results are analyzed incorporating viscoelasticity theory for power law time dependence of the matrix material, and it is demonstrated that the theory provides a less complicated presentation of the data by eliminating the superimposed effects of time dependent behavior.