Experimental and numerical investigation of the tension and compression strength of un-notched and notched quasi-isotropic laminates

Un-notched and notched (in the form of through-thickness open holes), quasi-isotropic AS4/3501-6 laminate coupons were tested in tension and compression. Basic lamina properties were also determined experimentally. Numerical analyses using linear elastic and progressive damage approaches were conducted. The linear elastic model either significantly underestimated (first-ply failure approach) or overestimated (last-ply failure approach) the strength of un-notched laminates. The progressive damage approach was able to predict accurately the un-notched strength, providing that the non-linear shear behaviour was accounted for and appropriate failure criteria used. It was also demonstrated that the progressive damage approach could be implemented, with satisfactory accuracy and efficiency, for open-hole strength prediction using basic material degradation laws, a shell element model and widely available commercial FEM software (ABAQUS). This is of practical use for industrial applications. In addition, for the purpose of comparison, a characteristic distance approach was also applied to the open-hole strength problem. It was found that using a linear analysis with a properly defined secant shear modulus this approach gave an accurate prediction, however at least one measured value of notched strength is still required for calibration using this approach.