Non-destructive testing/inspection of composite materials - acoustic impact testing, TV holography and shearography

This report provides an introduction to three different non-destructive testing/inspection (NDT/NDI) methods applicable for damage detection in composite materials. A lot of techniques have been developed for metals. However, composite materials often require other techniques, and the damages are often more difficult to detect, due to anisotropic material properties and combinations of materials with different mechanical behaviour and response. More experience is required for inspection and testing of such materials. The three inspection/testing methods covered in this report are acoustic impact testing, TV holography and shearography. Various techniques within the three categories of methods are developed, and for most of these the physical principle behind and the set-up is described. In addition, it is pointed out what types of damages, defects and material imperfections that may be detected with the different techniques, and what types of damages that are more difficult to detect. One NDT/NDI method is not able to detect all types of damages. Hence, there is a need for several techniques that can supplement each other.