Open-hole tensile strength and size effect of CFR polymers

The exact, anisotropic stress distribution of a laminate with a circular opening under uniaxial tension from Lekhnitskii’s theory is compared to Tan’s orthotropic approximation for several failure criteria. The predictions of these methods are compared to an extensive experimental campaign for validation. The campaign makes use of a carbon-fiber-reinforced epoxy unidirectional prepeg to manufacture orthotropic laminates of lay-ups [0]6, [90]6 and [0/90]2s. Lekhnitskii’s solution seems to provide a better prediction than Tan’s approximation in most cases for the tested laminates. This might to be due to the former being a better depiction of the real stress distribution for the orthotropic case. The improvements are negligible for quasi-isotropic laminates from the literature, but the proposed method provides a more general approach to most problems.