Effect of Edge Distance to Diameter Ratio on Progressive Failure of Bolted Joints in Laminated Composites

Abstract

The paper presents the progressive failure analyses of composite laminate single bolt joints for three different laminate ply stacking sequences and four edge distances. Failure of composite bolted joint is a multiscale, multimode failure event. Designs and/or load cases that lead to competing failure in multiple modes can be more difficult to predict and can be used as test cases to study predictability of failure and the ability to capture the failure mode interactions. The goal of the analyses was to identify bolted joint designs where the bearing failure mode and shear failure mode compete and collaborate with each other. Progressive failure analyses performed uses the Hashin’s failure criteria to define onset of damage and an energy-based continuum damage model with a smeared crack representation for material stiffness degradation as function of damage. For short edge distances since shear stresses dominate a nonlinear material model was used for the in-plane shear behavior. The progressive damage model was implemented as a user subroutine for explicit analysis (VUMAT) in ABAQUSTM finite element software. The model is validated from experimental pin bearing tests performed for two different materials. The results indicate by varying edge distance to diameter ratio and the proportion of 0, 45 and 90-degree plies in a laminates lead to design that exhibit multi-mode failure with interaction in the failure modes and resulting load paths. These designs with multimode failure and interactive failure can be more useful to choose for validation tests to assess accuracy of prediction models.