Determination of in-plane shear characteristics of composite materials with [+/-45 degrees] layup

The shear characteristics of a composite with a [+/-45 degrees] layer layup are measured experimentally by different methods. Investigations were conducted on flat and tubular specimens, The strength and shear modulus were determined by the rail method, the losipescu method, and by applying torsion to thin-wall tubes; only the shear modulus was determined by applying torsion to square plates. Determination of the shear modulus yields quantitatively comparable results, and, at the same time, the scatter of the shear-strength values of the specimens is significant. Maximum strength is achieved on the tubular specimens. The cause of the lower strength values of the flat specimens can be explained by secondary stresses and strains in their effective sections. The influence exerted by the geometry of the specimens on their strength is investigated for specimens tested by rite rail anti losipescu methods. It is shown that ir is possible to increase the strength appreciably by varying the specimen's geometry.