A finite element model for predicting time-dependent deformations and damage accumulation in laminated composite bolted joints

To assess and predict the long-term durability of advanced composite joints, a general, nonlinear finite element program was developed and implemented to model the localized time-dependent deformations and damage accumulation in the vicinity of a fastener hole in a polymer matrix composite (PMC) laminate. This code incorporates an elastic-viscoplastic constitutive model for unidirectional, orthotropic laminae, coupled with classical lamination theory, to determine the time-dependent stresses and deformations in the laminate. The accumulation of damage in the composite, and the subsequent deterioration of mechanical properties, is predicted by a set of ply failure criteria and an associated property degradation model. The results from this analysis were compared to experimental data and were found to provide reasonable correlation with time-dependent bolt-hole elongation measurements obtained from a graphite fiber reinforced PMC.