Composite Bonded and Bolted Joint Analysis Toolkit Based on Discrete Crack Network

Abstract

Both bolted and bonded joints have been used extensively in the integration and repair of composite structures. The load transfer provided by either a bolted or a bonded joint often drives the design under monotonic and fatigue loading. A composite bolted joint is a complex mechanical system that includes a plastically deformed bolt, damaged base and adjoint laminated plate, contact surfaces, and pretension in the bolt. An adhesively bonded composite structure of arbitrary configuration is also a complex mechanical system that includes local plastic deformation in an adhesive layer, intra damage and its associated stiffness degradation within a composite ply and/or within the adhesive, interface damage from debonding and delamination, contact between these delaminated interfaces, spatial distribution and evolution of the fabrication and environment variation induced residual stress, and the impact of temperature and moisture distribution within the bonded structure on the material properties and modeling parameters. Accurate evaluation of the 3D stress state from the joint system has a direct impact on the damage initiation and the resulting stress re-distribution. In order to accurately capture the damage evolution without remeshing and their associated energy dissipation, an extended finite element based approach for static and fatigue failure prediction of both bolted and bonded joints is developed for Abaqus via its user-defined element. To facilitate the model generation, property definition, contact and cohesive interface definition, and display of damage progression associated with matrix cracking and delamination, a composite bonded and bolted analysis toolkit for Abaqus (CB2ATA) is developed to simulate the discrete damage evolution under static and cyclic loading. A suite of verification and validation examples are use to demonstrate its applicability in the prediction of the first failure mode, post-peak softening, and fatigue damage accumulation of bonded and bolted composite structures.