Interlaminar stress recovery of multilayer composite shell structures for three-dimensional finite elements

Correct prediction of the onset of delamination requires an accurate evaluation of interlaminar stresses in multilayer composite laminates. An efficient interlaminar stress recovery procedure for three-dimensional finite element formulations is presented in [1] by the authors. The procedure is validated in [1] by analyzing moderately thick/thin composite plates of various geometries, and the results are compared with available exact and finite element solutions. These comparisons indicate that excellent agreement is obtained with exact solutions, and that convergence is reached using considerably fewer degrees of freedom compared to other finite elements procedures, thus making the procedure more suitable for design purposes. It is also shown in [1] that smooth distributions are easily generated without the need to employ smoothing techniques, as usually required instead using customary stress recovery procedures. Moreover, the procedure is shown to be as accurate as assumed stress methods using coarser meshes and without the need to include stress degrees of freedoms in the solution process. In this paper, the procedure is implemented in the commercial finite element software ABAQUS. A contact formulation is used to recover the inter-layer forces, thus, the method is applicable to general 3-D geometries and loadings. Benchmark problems concerning multilayer plate and shell structures are analyzed, and comparisons with ABAQUS’ built-in stress recovery and available solutions in the literature were used to confirm the accuracy of the procedure.