Experimental investigation of strength criteria for S-glass, E-glass and graphite fiber composite plate

Investigated are the Tsai-Hill and Tsai-Wu strength criteria for unidirectional S-glass, E-glass and graphite fiber reinforced composite plate specimens subjected to off-axis tension and compression. Off-axis shear is analyzed by using a circular specimen. The specimen contains almost collinear slits and antisymmetric cut-outs such that their orientation can change with the local axis to produce different combination of normal and shear action. Uniformity of the two-dimensional stress distribution in the center portion of the specimen is checked photoelastically. The stress coefficient F₁₂ in the Tsai-Wu criterion is determined experimentally for a normal extension and pure shear stress field; it is used to analyze the more general situations of off-axis tension, off-axis compression and off-axis shear. The results agreed well with experiments. Similar findings are obtained for the Tsai-Hill criterion except for the case of off-axis shear where large deviations occurred between analytical and experimental results.