Determination of the mechanical properties of composite materials by tensile tests. I. Elastic properties

Elastic constants as measured by means of tensile tests at different angles, are interrelated by the transformation rules. Based on these rules, a new data evaluation scheme is proposed to make tensile test data consistent. It also offers a way to measure the shear modulus and the shear-extension coupling constants by simple tensile tests. The method is applicable for all types of anisotropic materials. For strong anisotropy, the end-constraint effect can be accounted for in an iterative way. As an example, results are shown for a glass/epoxy woven fabric composite and for knitted fabric composites with monoclinic and triclinic symmetry. Next, the optimal test design is looked for: which tensile tests have to be performed to get the best estimate of the elastic constants? This problem is addressed both theoretically and by means of simulations for the case of woven and knitted fabric composites.