Post impact repair of in-situ polymerisable thermoplastic based carbon fibre composite and its assessment under compression after impact loading

This work investigates the impact response, associated damage, the feasibility of repair and strength recovery of infusible thermoplastic based carbon fibre reinforced composites. Impact behaviour of the laminates is studied using drop tower impact tests at three energy levels i.e. 40 J, 30 J and 20 J resulting in delamination as the primary damage mode at lower energy levels with evidence of fibre breakage at 40 J. Repair is performed by thermally re-consolidating impact damaged specimens under vacuum at a temperature above the glass transition temperature of the matrix. X-ray micro computed tomography (CT) scans and ultrasonic C-Scans reveal significant post repair re-consolidation. Compression testing using compression after impact (CAI) fixture resulted in a retained strength of 78 %, 88 %, and 93 % for impacts at 40 J, 30 J, and 20 J respectively. Post-repair compression strength using CAI tests, recovered 85 % of the pristine strength for 40 J impacts and close to 100 % of pristine strength for both 30 J and 20 J impacts. Thermography during CAI testing revealed a difference in the location of damage initiation under compressive loading for impacted and repaired specimens. The overall results highlight the potential for effective on-site repair and strength recovery using a relatively simple thermal re-consolidation procedure.