Composite materials have many advantages over conventional structural materials, particularly in primary structure. The advantages of composite materials include a high specific strength and stiffness, formability, and a comparative resistance to fatigue cracking and corrosion. However, not forsaking these advantages, composite materials are prone to a wide range of defects and damage during manufacture and in-service. The damage can significantly reduce the residual strength and stiffness of the structure or result in unfavourable load paths. Damage and defects can also reduce the functional performance of the composite component, such as leaking of pressure vessels and liquid tanks.