The Response of Composite Joints with Bolt-Clamping Loads, Part I: Model Development

Abstract

A three-dimensional model was proposed to analyze the response of bolted composite joints with and without lateral clamping forces from initial loading to ultimate failure. The effects of the clamping force, bolt stiffness, washer size on the response and failure of the joints were the major concern of the study. The model consists of a progressive failure analysis and a finite element stress analysis. For a given stress state in a joint, the progressive failure analysis predicts damage accumulated in composites by a set of failure criteria and estimates associated material degradation based on predicted modes of failure. To account for threedimensional bearing damage in joints, the model assumed that the material suffering from bearing damage became incompressible under lateral bolt constraints provided by the washers. In the stress analysis, the commercial finite element code ABAQUS was adopted to provide three-dimensional stresses and strains which are needed for the progressive failure analysis. A 3-D composite brick element was used, and slip/friction/ contact conditions were applied between the elastic bolt and a composite plate, and between the composite plate and the elastic washers or side plates. In order to reinforce the incompressibility condition for bearing-damaged material, the condition was imposed through a penalty method in the framework of finite element analyses. The proposed model was implemented in a code, namely 3DBOLT, in order to interface with the ABAQUS code. The code provides a user-friendly input deck, automatically generates a joint mesh, and produces output and graphics for displaying the stresses, strains, and deformations of the joints and for simulating the failure progression in joints during loading.