Unification of strength scaling between unidirectional, quasi-isotropic, and notched carbon/epoxy laminates

An investigation into size effects and notch sensitivity in quasi-isotropic carbon/epoxy laminates was carried out. The purpose is to draw a complete picture of the strength scaling in unidirectional, quasi isotropic, and notched carbon/epoxy laminates. A link was established between the strength scaling of the unidirectional and quasi-isotropic laminates. Efforts were made to understand the relationship between unnotched and open-hole strengths. For very small holes, the notched strengths approach the unnotched strength limit. A scaling law based on Weibull statistics was used to predict the unnotched laminate strengths. For very large holes, the same scaling law in conjunction with a detailed 3D ply-by-ply FE analysis with matrix cracks in the 90 degrees plies and delamination cohesive interface elements was used to predict the large notched strengths. A good agreement between the modelling and experimental results was achieved. The effects of 90 degrees matrix cracks on unnotched and notched strengths were also studied. (C) 2016 Elsevier Ltd. All rights reserved.