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Discrete Damage Modeling of complex local failure patterns in laminated composites including matrix cracking, delamination, and fiber failure was performed. Discrete Damage Modeling uses the Regularized eXtended Finite Element Method for the simulation of matrix cracking at initially unknown locations and directions independent of the mesh orientation. Cohesive interface model is used both for Mesh Independent Cracking as well as delamination propagation. The fiber failure mode is modeled by two different methods in tension and compression. Tensile failure is predicted by Critical Failure Volume criterion, which takes into account volumetric scaling of tensile strength. Compression fiber failure is simulated with a single parameter continuum damage mechanics model with non-compressibility condition in the failed region. Ply level characterization input data were used for prediction of notched and unnotched laminate strength. All input data required for model application is directly measured by ASTM tests except tensile fiber scaling parameter and compression fiber failure fracture toughness, which were taken from literature sources. The model contains no internal calibration parameters. Tensile and compressive strength of unnotched and open hole composite laminates IM7/977-3 has been predicted and compared with experimental data. Three different layups, [0/45/90/−45]2S, [30/60/90/−60/−30]2S, and the [60/0/−60]3S, were modeled and tested and showed good agreement with experiment in the case of tensile loading, whereas the compressive strength was generally under predicted for unnotched laminates and overpredicted for open hole laminates.

Meso-scale geometrical changes during transverse compression of aligned tows have a significant influence on resin permeability during infusion as well as on the mechanical properties of the resulting polymer composites. These geometrical changes need to be captured at each and every stage of composite manufacturing and realistic geometrical models verified by accurate experimental data are needed to simulate the changes during forming to predict the mechanical properties of the composite laminates. In the present work, the aligned fibre tows in a dry plain woven glass fabric are simulated by digital element method. A meso-scale compaction study of the tow geometrical changes has been conducted by 3D X-ray computed tomography (CT) under compression loading. The evolution of mesoscale geometrical features such as tow area, thickness, width and waviness has been quantified using high quality CT images. The realistic tow geometrical data by digital element simulation under different compaction levels has been validated by experimental data obtained by CT.

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