In aerospace manufacturing and maintenance, repair and overhaul (MRO), there are many nondestructive testing (NDT) techniques for aluminum and steel, but far fewer options for carbon and glass fiber-reinforced polymer (CFRP, GFRP) composites.
Given the multi-layered, anisotropic nature of these materials, flaws like cracks, porosity and foreign bodies can occur on the surface or within a particular layer of fiber or resin with no predictable orientation. Delamination defects can propagate quickly,
Source: NDT
