Design and analysis of mechanically fastened composite joints and repairs

Abstract

In this paper, a boundary element formulation is developed to analyze mechanically bolted composite joints and repairs. Boundary equations are formulated for all the member panels of the composite joints/repairs. These equations are solved together with the fastener equations to get the resultant contact forces for all the fasteners involved. The fasteners are modeled as 1-D springs that are governed by linear relationships between the fastener forces and the displacements of member panels at the respective fastener centers. After obtaining the fastener forces from the so-called global analysis, detailed stress analyses are conducted for regions around individual fasteners. The stress distributions around fastener holes are then used to evaluate the margin of safety of the composite panels. The numerical predictions on the fastener forces, failure modes and failure loads of two composite joints using this method agree very well with experimental results. The boundary element formulation presented here is especially suitable for design and analysis of aircraft battle damage repairs where time and facility availability is the prime concern.