Adhesively bonded single lap joints with GFRP and CFRP composites in maritime conditions: A comparative study

Abstract

Composites consisting of two or more different macroscopic structures are becoming increasingly popular. This study investigates the long-term effects of single lap-joined GFRP and CFRP specimens on the material after exposure to seawater. Seven-ply GFRP and eight-ply CFRP composite materials were used under dry (without immersion in sea water) conditions and by hand lay-up method. Both GFRP and CFRP samples were 0/90 oriented twill braided. In September, sea water at 23.5°C temperature in Izmir province (Selçuk/Pamucak) region was kept in different containers for 1 month (30 days), 2 months (60 days), and 3 months (90 days) separately for GFRP and CFRP composites. They were cut for single lap joints according to ASTM D5868-01. Axial impact tests and moisture retention percentages were performed. Three-point bending tests were then performed in accordance with ASTM D790. Moisture retention rates (%), axial impact tests, and three point bending test specimens were kept in seawater with 3.3%–3.7% salinity for 1, 2, and 3 months. As a result of the three-point bending tests, it was observed that the Young modulus of the GFRP single lap joints decreased by 5.94%, 8.90%, and 12.98%, respectively, compared to the dry joints held for 1, 2, and 3 months. It was observed that the Young modulus of the CFRP single lap joints decreased by 1.28%, 3.39%, and 3.74%, respectively, compared to the dry joints held for 1, 2, and 3 months.