Composite Materials

· Laminates subjected to fatigue loading can also fail under the influence of these complex stress distributions.
· The top diagrams shows the initiation of ply cracking as a function of the number of load cycles normalized by the number of cycles to failure, the cycle ratio.
· The lower diagram displays the amount of delamination between laminae (as a result of crack propagation parallel to the inter-lamina boundary) as a function of the cycle ratio.

From: Schaffer, et al, "The Science & Design of Engineering Materials," Irwin (1995)