Extension-shear coupled laminates with immunity to hygro-thermal shearing distortion

Material-independent necessary and sufficient conditions are derived for extension-shear coupled laminate with immunity to hygro-thermal shearing distortion (HTSD) using classical lamination theory. It is proven that no standard form of extension-shear coupled laminate with immunity to HTSD exists. A survey is performed to identify free form of extension-shear coupled laminate with immunity to HTSD that produce maximum extension-shear coupling. This is achieved through a constrained optimization routine, where the constraints are the material-independent necessary and sufficient conditions for laminates with immunity to HTSD. Results are presented for the symmetric laminates that consist of 8-14 plies. Comparisons are made on hygrothermal behavior and buckling strength of extension-shear coupled laminates with and with immunity to HTSD. The robustness of the extension-shear coupled laminates with immunity to HTSD is verified by using Monte Carlo simulation for laminates with fiber orientation that slightly deviates from the theoretically designed direction.