The Influence of Geometry on Failure Modes of Countersunk Bolted Hybrid Joints

Abstract

This paper presents a numerical study for the influence of geometry on the damage initiation and growth in the CFRP (Carbon Fiber Reinforced Polymer) laminated plate of the hybrid metal-composite countersunk bolted joints. A detailed 3D finite element model incorporating material and friction-based contact full nonlinearities is developed to investigate the geometry effects on the failure modes of the hybrid metal-composite bolted joints. The material model for CFRP joint counterpart integrates nonlinear shear response for unidirectional laminae, Hashin-type failure criteria and strain-based continuum degradation rules which were developed using the UMAT user subroutine in MSC. Patran-Nastran (MSC. Software Corporation Inc.) commercial software. Experiments were conducted in order to validate the nonlinear progressive damage analysis (PDA) results on the failure modes of the joints with countersunk bolts. The numerical and experimental results showed that the joint geometry parameter defined by the ratio between the plates width and hole diameter has an important influence in designing phase of a reliable bolted joint and its effects on damage initiation and failure modes were quite accurately predicted by the numerical model, which proved to be computational efficient and could predict damage mechanisms in hybrid metal-composite countersunk bolted joints.