The effect of modified tannic acid (TA) eco-epoxy adhesives on mode I fracture toughness of bonded joints

Two synthesized eco-epoxy components based on TA: (A) glycidyl ether and (B) phosphate ester, are used, as a replacement for the Bisphenol A (BPA) epoxy component, bonding aluminum (Al) carbon fiber reinforced polymer (CFRP). Their effect mode I fracture toughness (GI) is evaluated by Double Cantilever Beam (DCB) testing while using Digital Image Correlation (DIC) in-situ crack tip monitoring. Compared to reference adhesive, an improvement of Al (43%) CFRP (100%) obtained when adhesive B. Moreover, regardless adherend material, stick-slip pattern growth observed. Weak adhesion leads failure vs. cohesive-adhesive in case On contrary, modification has adverse GI (−33%) (−78%) opposed their counterparts.