A comparative study on the adhesive bonding strength of unidirectional, 4-Harness Satin weaved and plain weaved carbon fibre reinforced polymer after KrF excimer laser pre-treatment

Abstract

Several types of carbon fibre reinforced polymers (CFRP) are available based on the appearance of the carbon fibre laminates. In this study, three distinct types of CFRPs, namely, unidirectional (UD CFRP), 4-Harness Satin weaved (4HSW CFRP) and plain weaved (PW CFRP) were selected to compare the bonding strength performance of specific CFRP/CFRP adhesive joints after KrF laser pre-treatment. KrF excimer laser with top hat beam profile was utilized. This treatment increased the Sq and Sdr values significantly for all three CFRP types. KrF laser affected the matrix polymer C-N bonds and converted the tertiary and secondary aliphatic amines to secondary and primary amines, respectively, after de-polymerization. Single lap shear stress (SLSS) test revealed that the average adhesive bonding strength achieved respectively for UD CFRP, 4HSW CFRP and PW CFRP after KrF laser pre-treatment were 32.80, 23.97 and 35.21 MPa which were 104.34%, 47.24% and 39.72% higher than their pristine counterparts. Repeatability of the SLSS results were more for weaved pattern CFRPs. Adhesive failure reduced drastically and presence of cohesive failure, thin layer cohesive failure and fibre tear failure were prevalent in SLSS for all considered CFRPs. Comparison of all results showed that the best performance was obtained for PW CFRP.