The Effect of CO2 Laser-Induced Microhole Formations on Adhesive Bonding Strength of CFRP/CFRP Joints

There are many different techniques to improve the adhesion between carbon fiber-reinforced plastics (CFRP) which are used in aircraft primary structures. One of the most common techniques is the specific surface structuring of the joining parts in order to obtain mechanical interlocking. In this study, laser-induced surface structuring effect on adhesion strength of CFRP/CFRP joints was investigated by single lap shear tests. Microholes were created by CO2 laser with different configurations in x and y axis for the best mechanical interlocking effect on adhesive bonding. The effects of microhole numbers (309, 625, and 914) and microhole formations (triangle, inverted triangle, frame, and box) on the adhesive bonding strength of the CFRP/CFRP joints were determined by using single lap shear tests according to ASTM D5868-01 standard with 60 kN DARTEC universal test machine. Single lap shear tests showed that microhole structuring has a significant effect on mechanical interlocking for adhesive bonding of CFRP/CFRP joints. Results showed that the shear strength of CFRP/CFRP joints improved at 309 microholes and frame type microhole formations. After mechanical tests, damage mechanisms were observed by using the optical microscope. POLYM. COMPOS., 40:2891-2900, 2019. (c) 2018 Society of Plastics Engineers