Three-dimensional finite element analysis of single-bolt, single-lap composite bolted joints: Part I - Model development and validation

Three-dimensional finite element models have been developed to study the effects of bolt-hole clearance on the mechanical behaviour of bolted composite (graphite/epoxy) joints. The joint type studied was single-bolt, single-lap, which is a standard test configuration in both a civilian and a military standard for composite joints. In this Part I of a two part paper the model is constructed in the non-linear finite element code MSC.Marc and attempts are made to validate it by comparing results with experiments and other finite element solutions generated in a European project on composite bolted joints. Issues in modelling the contact between the joint parts, which affect the accuracy and efficiency of the model are presented. Experimental measurements of surface strains and joint stiffness are compared with results from a finite element parameter study involving variations in mesh density, element order, boundary conditions, analysis type and material modelling. The ability of the models to capture three-dimensional effects such as secondary bending and through-thickness variations in stress and strain is evaluated, and the presence of mathematical singularities in such models is highlighted. The validated model is used in Part II to investigate the effects of clearance on joint stiffness, stress state and failure initiation.