Viscoelastic and Nonlinear Adherend Effects in Bonded Composite Joints

Abstract
An experimental and theoretical investigation is described on the effects of viscoelasticity and geometric and material nonlinearity in rubber-toughened graphite/epoxy adherends. Single-lap joints, with adherends of a matrix-dominated layup and a brittle epoxy adhesive layer, were tested under two constant loading rates to failure; axial strains were measured at several locations on the surface of the adherends. Aluminum and fiber-dominated laminate adherends were also studied for comparison. Finite element analyses of the adhesive joint were made using linear and nonlinear viscoelastic characterizations of the composite. The experimental work is discussed first. Then we describe the constitutive theory and its implementation in the finite element analysis, after which the theoretical ane experimental results are presented and compared.