Residual Strength Evaluation of Typical Aircraft Composite Structures with a Large Notch

Karayev, K.Z., Minguet, P.J., Lee, S., Balabanov, V., Muraliraj, N., Walker, T.H., Nelson, E.E.

Robbins, D., AIAA 2012-1862, 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Honolulu, Hawaii, 23 – 26 Apr 2012.

The progressive failure analysis (PFA) method, based on the commercially-available software Helius:MCT™, was applied for Residual Strength Evaluation (RSE) of unstiffened notched composite panels using the ABAQUS/Standard finite element code. The analysis parameters and modeling technique (i.e., mesh size and pattern, boundary conditions, etc.) were defined by calibration to test data. The calibration database consisted of eleven center-notch panels fabricated from Carbon Fiber Reinforced Plastic (CFRP) tape. Multiple layups were tested, ranging from very soft to very hard, and were selected to cover the possible range of failure types and damage morphologies. Different notch sizes were also included. Tensile loading was applied to all panels, except one panel where the tensile load was combined with in-plane shear. The resulting FE technique and analysis parameter settings were validated by comparison with additional test data not included in the calibration. The method was also applied to panels fabricated from a different material system. It was determined that the delamination between plies must be simulated to obtain accurate results for hard laminates. In the developed method, delamination is simulated using cohesive elements. Numerous options for the interfaces and dimensions of the cohesive-element region were studied, and critical interfaces were identified. The definition of these critical interfaces is described in the paper. The effect of the cohesive element size will be investigated in the future.