| Composite materials have various failure modes, which often coexist and interact. Interply delamination is the most frequently observed of these failure modes in laminated composite. Much previous research has been conducted to investigate the delamination phenomenon, often using computational mechanics approaches. The majority of the existing analytical models employ a zero thickness interface element to represent the delaminating interply region. This type of modeling requires explicit modeling of the delamination, which is not suitable for thick section composites. This type of modeling also introduces difficulties in predicting mode mixture.; Two structural modeling approaches are proposed herein. The first one involves explicit modeling of the delamination crack, which is suitable for thin section composites. The second incorporates the delamination behavior into a homogenized constitutive model, which is appropriate for thick section composites. Both approaches utilize a nonlinear interface model with finite thickness, which models the resin rich interply zone explicitly. The thickness of the interface is treated as a constitutive parameter. An Elastic damaging model is adopted to characterize the nonlinear behavior of the interface.; Several interlaminar fracture toughness tests are simulated for calibration and validation purposes. Pure mode nonlinear properties of the interface are calibrated by trial-and-error matching of P-δ curves from selected experiments. These properties are then used to simulate independent mixed mode tests for validation. Predictions of behavior and mode mixture are reasonably good, and dissipated energy due to damage also exhibits good agreement with experimentally obtained energy release rate values.; For thick section composites, the proposed interface model is incorporated into an existing homogenized constitutive model. The interface is treated as one of the layers constituting the repeating sublaminate, which is the basic building block of the thick section laminate. This homogenized model is used to analyze several notched plates and cylindrical shell panels for which experimental results are available, and found to be capable of representing local delamination as well as global structural behavior. |
