Acoustic emission monitoring of repaired composite laminates

This paper presents the results of an experimental investigation conducted to study the strength of different repair technique on impact damaged glass fibre reinforced plastics (GFRP) using the acoustic emission technique. ASTM D3039 tensile specimens (250 mm x 18 mm x 2 mm) fabricated using bi-directional glass fibre and epoxy resin are impacted at low energy (1.89 J) so as to produce a limited yet visible amount of damage. Subsequently, the damaged region is repaired using different methods. These include the bare removal of impacted region ("dressed" sample), taper sanded ("scarf") repair or the application of single lap technique. Subsequently, the impacted and differently repaired samples have been subjected to tensile loading to failure monitored using acoustic emission to evaluate the quality of repair obtained, in particular distinguishing between the different failure modes obtained during post-impact tensile tests, namely matrix cracking, delamination and fibre breakage, according to the classification information obtained in previous literature. This allows understanding which mode of failure is dominant in each case and possibly proposing which might be the most suitable repair method for these laminates.