A novel approach for the three-point flexure test of multidirectional laminates

The complementary energy of a multidirectional laminate is obtained as a function of mechanical and hygrothermal force and moment resultants. Three-point flexure is then analysed assuming that the specimen is in contact with the support rollers at four points. As this problem is statically indeterminate, the redundant force is obtained by applying Engesser's second theorem. Lift-off at supports is assumed to occur when the redundant unknown is zero. The displacement field of a multidirectional laminate in three-point flexure is then obtained by applying Engesser's first theorem, including transverse shear and hygrothermal effects. The displacements related to bending and twisting moments, hygrothermal effects and transverse shear forces are analysed separately.