Tap testing of composites benchmarked with digital shearography

This paper reports on two non-destructive testing techniques employed to detect subsurface defects in composite materials of both the monolithic and sandwich types. Making use of the NDT techniques named in the title of this paper, digital shearography was used to benchmark the results obtained through the tap testing method. The tap testing was performed using the Mitsui Woodpecker WP-632AM, a handheld automated impact instrument that displays the defects' positional data (X-Y coordinates) on a PC in real time. The versatility and ease of use of the Woodpecker is abundantly demonstrated and comparisons with the results obtained using digital shearography on the same test specimens have given an indication of its accuracy.