Comprehensive Bonded Joint Analysis Method

M4 Engineering, Inc. and Sandia National Laboratories propose to create a unique bonded joint analysis and design software tool. Surrogate traction-separation models will be created that efficiently capture the behavior that occurs for real bonded joints. Mixed mode loading, including compressive normal tractions and relative displacements will be captured and used in an extended cohesive zone element to be developed and implemented in ABAQUS using its user subroutine interface. The mathematical forms for the surrogate traction-separation interface models will be developed and populated using high fidelity numerical models which include explicitly modeled adhesive layers. These models will utilize the nonlinear viscoelastic constitutive equation for polymers developed at Sandia. This material law captures the complete range of polymer behavior which cannot be captured fully by any known plasticity model. Furthermore, not only is this model useful for simulating variable thermal histories, it is also useful for predicting both adhesive and cohesive failure of polymer epoxies, as shown in the literature. An experimental program necessary to fully populate the high fidelity models and validate the surrogate traction-separation models will be delineated. Successful execution of this proposal will allow a commercially viable software tool to be developed in Phase II.