On some aspects of the modified TSAI-WU criterion in thin-walled composite structures

For anisotropic materials, Tsai-Wu [J Comp Mater 5 (1971) 58] proposed the failure criterion that takes into account the difference in strength due to positive and negative stresses. Hashin [J Appl Mech 47 (1980) 329] pointed to some internal incoherencies of the function of material effort with respect to stress parameters. The minimum of the External Function does not coincide with the unstressed state. Therefore, the criterion presented by Tsai-Wu [J Comp Mater 5 (1971) 58] has limited possibilities of application for optimization purposes. A modification of the Tsai-Wu criterion, needed in the case of the multi-criterion optimal design of thin-walled composite structures, has been presented. A proposal of the evaluation of the load carrying capacity of multi-layered composites with respect to their failure mode has been put forward.