Application of Tsai-Wu criterion to notched and unnotched composite laminates under torque loading

This work deals with the behaviour of composite laminates under static torque loading. The stress distributions in notched and unnotched unidirectional composite laminates based on an analytical study and a finite element calculation are discussed. The Tsai-Wu failure criterion is applied locally in three-dimensions to predict the initiation of damage and sites of local failure are detected by in-situ observations of the fracture surfaces in the scanning electron microscope (SEM) that confirm this prediction. With the help of the schematic model of acoustic emission, each type of damage mechanism and their development process during twisting are described empirically and phenomenologically. These investigations give a better understanding of the damage process and provide useful information in establishing quantitative representation, including the controlling factors and mechanisms for composite laminates subjected to torsion.