Abstract
Laminate configurations of some composite plates for practical use can be considered to be quasi-orthotropic. In the present paper experimental results on tensile strength of laminates with loaded and unloaded circular holes are described. The plates are made of carbon fibre reinforced plastics and can be considered to be either quasi-isotropic or quasi-orthotropic. The experimental results are compared with the calculated first failure strength. The calculations are made by applying Lekhnitskii's stress expression for orthotropic plates with circular holes and Zhang and Ueng's approximate stress expression for orthotropic plates with pin-loaded holes. The calculated strength is much lower than the experimental one as expected. Some consideration about the discrepancy is given.