Comparing Mode I, Mode II and Mixed-Mode I/II interlaminar fracture toughness of glass and carbon fiber reinforced polymer laminates with the same epoxy matrix system

• Quasi-static Mode I, II and I/II toughnesses are higher for GF- than for CF-epoxy. • GF- and CF-epoxy fracture toughness differs most for Mode II and least for Mode I. • Two Mixed-Mode I/II setups at 4:3 ratio are compared for GF- and CF-epoxy. • Fixed-Ratio Mixed-Mode and Mixed-Mode Bending tests yield comparable results. Quasi-static delamination resistance tests under Mode I, Mode II and Mixed-Mode I/II loading are performed on unidirectional (UD) glass fiber (GF) and carbon fiber (CF) reinforced polymer laminates manufactured with the same epoxy matrix. Compared to the CF-, the GF-epoxy laminate has a higher fracture toughness under all loading modes. Fracture toughnesses differ the most for Mode II and the least for Mode I loading. Mixed-Mode I/II fracture toughness is determined in Fixed-Ratio Mixed-Mode and Mixed-Mode Bending tests, performed at the same Mixed-Mode I/II ratio of 4:3. The two test methods yield comparable results for UD GF- and UD CF-epoxy.