An experimental investigation into size effects in quasi-isotropic carbon/epoxy laminates with sharp and blunt notches

Abstract

An experimental investigation into size effects in notched [45/90/-45/0] 4s carbon/epoxy laminates is carried out. The in-plane dimensions of the quasi-isotropic laminates are scaled by up to a factor of 8. Larger Scale 16 specimens with only their width and notch length being doubled were also tested as a further comparison. Interrupted tests and X-ray Computed Tomography (CT) scanning are carried out to study the damage at the crack tips. Sharp centre-notched tensile tests are compared to open-hole tests of the same notch length (hole diameter), material and stacking sequence. A similar strength reduction scaling trend is found for both configurations at the small sizes, except with higher tensile strength for the centre-notched specimens than the open-hole specimens. However, there is a cross-over point when the sizes increase, with the sharp notched results approaching an asymptote based on Linear Elastic Fracture Mechanics (LEFM), and the open hole results approaching an asymptote based on Weibull theory.