End reinforcement of composite cylinders for biaxial testing

Abstract

A detailed theoretical investigation has been carried out into factors affecting external end reinforcement of GRP (glass-reinforced plastic) cylindrical specimens for biaxial tests using axisymmetric solid finite elements. The reinforcement method is intended as a general solution to a wide range of applied axial and hoop stresses in the third quadrant of the stress field. Among the parameters considered were the ratio of hoop-to-axial stress, material employed for reinforcement, thickness, length and taper angles of the reinforcement layers. The assessment of the effective control of high discontinuity stresses at the fixed ends by the end reinforcement was made with the help of the Tsai-Wu strain index distribution and decay length of the bending stresses. The paper also describes the preliminary experimental work to show the effectiveness of an external composite reinforcement method in controlling the strain distribution of GRP cylinders closed by rigid end flanges.