An approach based on damage tolerance is proposed for the design of bolted composite joints. The approach requires knowledge of failure processes and damage accumulation in composites under physical loading. Based on experimental observation, a progressive damage model was developed for predicting the accumulated damage and failure modes in composite joints.
In order to utilize the model for design, a computer code, 3DBOLT, has been developed. The code is based on the progressive damage model, and it interfaces with the commercial finite-element code ABAQUS to perform calculations of three-dimensional stresses, strains, and deformations of the joints for a given load. for a given joint configuration, ply orientation, and loading condition, the code can predict the response of the joint from the initial loading to final failure, estimate accumulated damage in the joint as a function of applied load, and predict the joint deformations. In order to verify the proposed damage model, the data obtained from the experiments were compared with the predictions from the 3DBOLT/ABAQUS code. Based on the code, a parametric study was performed to characterize several important factors that can significantly influence the design of bolted composite joints.