Durability under fatigue loads

Fatigue damage may initiate and grow along any material interface. Damage modes include fibre breakage, matrix cracking, fibre pull-out, mixed-mode delamination. For compression loading, local or global buckling may also occur. Once a damage has initiated, its growth is driven by strain energy released to create new surfaces. Damage in composites grows progressively and includes multiple damage types. Hence the fatigue durability of composite structures is mostly assured by performing adequate fatigue tests. Different approaches are used to account for the scatter associated with fatigue of composite materials.

These include:

	Life factor approach
	Load enhancement approach
	Specrum truncation