Mechanical characterization of angle-ply composite laminates by differential Moire method: The influence of specimens' length-to-width ratio

The influence exerted by the specimen proportions on the measured performance of angle-ply [+ 45 degrees/- 45 degrees](s)composite laminates is studied. Three kinds of specimens are considered, having different length-to-width ratios, made with glass/epoxy unidirectional or fabric laminae. The static tensile characteristics are measured by means of load cells, electric strain gauges and through the Moire fringes method. The strain fields are analysed and the effects of stress concentration at the laminate-free edges are evaluated, as well as their influence on the strain distribution and themeasured strength and stiffness. The results are summarized as diagrams ofultimate load and elastic modulus versus length-to-width ratio of the different specimens investigated. These diagrams allow the designer to evaluatethe influence exerted by specimen proportions on the measured performance,as well as to compare characteristics which are heterogeneous, as obtainedwith different kinds of specimen.