Determination of the mechanical properties of composite materials by tensile tests. II. Strength properties

A new data evaluation scheme is presented for the measurement of tensile strengths at different angles. The method is applicable for all composite materials that follow the Tsai-Wu failure criterion. It is general in the sense that it can be used for both triclinic and monoclinic or higher symmetry materials. With this method, tensile strength data at different angles can be made consistent. It is also shown that the shear strength can be determined by tensile tests if in addition a biaxial test and two or three compression tests (for, respectively, monoclinic or higher symmetry and triclinic materials) are performed. As an example, the method is applied to a glass/epoxy woven fabric composite and two types of knitted fabric composites. The best test angles to determine the strength parameters for these materials happen to be the same angles that were optimal for the determination of the elastic properties. (Author)