Experimental assessment of drilling-induced damage in impacted composite laminates for resin-injection repair: Influence of open/blind hole-hole interaction and orientation

An experimental study of drilling-induced damage in barely visible impact damaged (BVID) carbon fibre reinforced polymer (CFRP) laminates where small circular holes were intentionally drilled into the impacted zone as an intermediate step of the resin-injection repair process was described. In-plane compression testing was conducted to determine the mechanical properties of BVID specimens containing open/blind, single and binary holes. Binary-hole specimens at fixed distance apart were tested in parallel or normal to the applied uniaxial force. As expected, BVID specimens experienced significant diminution of property value (compared to pristine ones). No dependence of mechanical properties on hole-hole orientation was observed. Owing to the large hole-hole separation, this significantly mitigated the hole-hole interactions, even though the predicted stress concentration (around the holes) level was above the residual strength. Interestingly, single/binary-hole BVID laminates generated counter-intuitive laminate stiffening effects that the stiffness was significantly higher than that of undrilled BVID specimens.

Automated summary

Experimental study showed that drilling-induced damage in BVID CFRP laminates led to significant reduction in mechanical properties, but single/binary-hole BVID laminates could generate counter-intuitive laminate stiffening effects.