Implementing surface treatment and adhesive variations for bonded joints between composite gfrp and aluminum at 200 °C

Abstract

Bonding dissimilar materials, specifically Glass Fiber Reinforced Polymer (GFRP) and Aluminum 6061 T651, at elevated temperatures, such as in fire accidents is challenging, where structural integrity and reliability are critical. We studied how surface roughness treatment affects the joint strength of three common adhesives in aircraft (Click Bond CB394-43, Loctite A9396, A9394) at 200 °C. The GFRP, composed of Gurit Prime 37 epoxy resin and E-Glass 7781 fibers produced through vacuum infusion with dimensions following ASTM D5868 standards, was lap shear tested with 2 mm/s stroke. Findings showed a substantial enhancement in joint strength due to surface treatment, sanding with 100-grid sandpaper for 20 seconds in parallel with the fiber direction, for all adhesives. A9396, A9394, and CB394-43 exhibited remarkable improvements of 1091.67 %, 45.92 %, and 30.09 %, respectively. The strain at break showed significant increases of 51.61 %, 121.95 %, and 100 %, respectively. Both surface-treated and untreated A9394 samples showed the highest strength among the adhesives. A9396 exhibited lower strength than CB394-43 without surface treatment, but it outperformed when surface-treated, highlighting its response to surface modification. Adhesive viscosity influences penetration on material surfaces, with A9396 being stiffer than the other adhesives. The analysis of ISO 4287 Ra values revealed that surface treatment led to increased roughness on the Aluminum surface while reducing roughness on the GFRP surface. These results offer valuable insights for optimizing GFRP-Aluminum bonding under elevated temperature conditions. Adjusting surface roughness significantly improves the interaction between Aluminum and GFRP with adhesives, resulting in enhanced joint strength. This knowledge can be applied in various engineering applications, particularly in industries where the performance and reliability of bonded joints are critical under high-temperature environments