Effects of scratch damage on progressive failure of laminated carbon fiber/epoxy composites

Composite structures in practice can be subjected to various types of damage such as abrasion with sharp objects. This damage can result in gouges or damage resembling deep scratches that can impact one or more plies. In this study, the effects of scratch geometry on the delamination of a laminated composite under tensile loading are investigated using experimental and numerical analysis techniques. A numerical approach based cohesive zone models is used to simulate the progressive failure of the composite specimen containing scratches. Scratches at different depths in carbon fiber-epoxy laminates are modeled to study the influence of the scratch tip and its interaction with the stacking sequence. Experimental results show the interlaminar crack propagation has good correlation with the proposed modeling approach for initiation and propagation load levels. These deformation modes are validated with a full-field digital image correlation assessment. The results indicate that the scratch tip location within the stacking sequence is a dominant factor for tension load capacity associated with the scratch depth and geometry and can result in undesirable bending and torsional deformations, further driving the delamination response.

Cohesive/failure of damage progression in scratched composites.
► Modeling capable of predicting initiation and propagation of cracks at damage sites.
► Scratches in symmetric layups cause significant twisting and bending deformations.
► Layup has significant effect on crack initiation load.