3. Translaminar fracture toughness in composites

3.1 0° ply fracture toughness versus laminate fracture toughness

As previously mentioned, toughness in multidirectional laminates depends significantly on the orientation of the fibers within each ply. Ideally, we should be able to determine the toughness of each type of ply, for example 0°, 90°, 45° and – 45° in the standard cases, and then trace the toughness of the laminate back to homogenization. This is the approach adopted in classical laminate theory, which allows us to pass from the stress flows imposed on the laminate to the stresses in each ply