Fracture toughness in SPCC/CFRP hybrid laminates: Mode I and mode II perspectives

Hybrid composites using adhesive joints are gaining popularity in various industries as their various material combinations can create certain advantages. This research focuses on examining the mode I and mode II fracture toughness characteristics of the combined laminate between Steel Plate Cold Rolled Commercial (SPCC) metal and Carbon Fiber Reinforced Polymer (CFRP) composite processed using adhesive bonding. SPCC/CFRP hybrid laminate composites were manufactured with a variety of manufacturing options (A, B, and C) to find the most optimal method using two types of epoxy and cyanoacrylate adhesives, with two different bonding processes: secondary bonding and co-bonding. Fracture toughness values were measured through the Double Cantilever Beam (DCB) test for mode I and the End Notched Flexure (ENF) test for mode II. The test results showed that epoxy adhesives in the SPCC/CFRP adhesive joints provided better fracture toughness performance, especially when combined with the co-bonding technique. Specimens from manufacturing option C showed the highest G IC and G IIC values of 83.05 and 254.94 J/m 2 , respectively. These values increased by 58.98% and 80.48% compared to manufacturing options A and B in Mode I. Additionally, the G IIC value for manufacturing option C increased by 78.00% and 66.76% compared to manufacturing options A and B. The SPCC/CFRP hybrid laminates showed adhesive failure on the SPCC surface when using epoxy adhesive, whereas adhesive failure occurred on the CFRP surface with cyanoacrylate adhesive for the different manufacturing options. • Hybrid SPCC/CFRP laminates were tested for fracture toughness using epoxy and cyanoacrylate adhesives. • Manufacturing option C (epoxy and co-bonding) showed the highest G IC (83.05 J/m 2 ) and G IIC (254.94 J/m 2 ). • Option C's G IC increased by 58.98% and G IIC by 78% compared to other methods. • Epoxy outperformed cyanoacrylate, especially with co-bonding. • Failure modes varied, with option C showing mainly adhesive failure on SPCC.