How do I inspect my structures for damage & quality control?

Defects or damage can be introduced:

• during manufacture (e.g. embedded voids or inclusions)
• during installation (e.g. handling damage or accidental impact during positioning or transport)
• during component service life (e.g. fatigue damage, impact damage, overload)

The method for checking for damage during service intervals should be assessed at the design stage for complex safety critical components. In some cases, continual monitoring of the component stiffness is practical and this can also be used as a method to identify the introduction of damage into a component. The most used method is visual inspection looking on the outside surfaces for matrix or fibre damage, dents, or seepage if the structural purpose is fluid containment.

Non destructive testing refers to a collection of testing techniques that can be used to inspect for damage without further damaging the component. They can be used to determine both the nature and extent of any damage. NDT techniques allow components to continue to be used in service if no critical defects are located. The development of these techniques has been pushed forward by the aerospace industry where composites are used in many safety critical applications. For safety critical applications, inspection schedules must be set and maintained.

Often, damage in composites is difficult to assess from a surface inspection alone. NDT techniques are of great assistance when working with laminated composites where delamination and internal cracking are possible failure mechanisms. Commonly used forms of NDT include:

	Ultrasonics
	X-ray
	Thermography
	Shear interferometry
	Lamb Waves