Advances in Titanium/Polymer Hybrid Joints by Carbon Fiber Plug Insert: Current Status and Review

• Published in: Materials Vol. 15; no. 9; p. 3220
• Main Authors: Faudree, Michael C, Uchida, Helmut Takahiro, Kimura, Hideki, Kaneko, Satoru, Salvia, Michelle, Nishi, Yoshitake
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 29.04.2022; MDPI
• Subjects: ABS resins; Acrylonitrile butadiene styrene; Adhesion; Adhesive bonding; Aircraft; Bond strength; carbon fiber; Carbon fiber reinforced plastics; Carbon fibers; Chemical bonds; Crack propagation; Crystallites; Electron beams; Electron irradiation; Fan blades; Fasteners; Fiber reinforced polymers; Hot pressing; hybrid joint; Jet engines; Lasers; Literature reviews; Low voltage; Mechanical properties; Plugs; Recyclability; Review; Shear strength; Shear tests; spot-welding; Stress concentration; thermoplastic; thermoset; Titanium; Titanium alloys; Ultimate tensile strength; thermoset; carbon fiber; titanium; electron beam; spot-welding; thermoplastic; hybrid joint
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma15093220

A literature review of up-to-date methods to strengthen Ti/carbon-fiber-reinforced polymer (CFRP) hybrid joints is given. However, there are little or no studies on Ti/CFRP joints by carbon fiber plug insert, which takes advantage of the extremely high surface adhesion area of ~6 μm CFs. Therefore, we cover the current status and review our previously published results developing hybrid joints by a CF plug insert with spot-welded Ti half-lengths to enhance the safety levels of aircraft fan blades. A thermoset Ti/CF/epoxy joint exhibited an ultimate tensile strength (UTS) of 283 MPa when calculated according to the rule of mixtures (RM) for the CF cross-section portion. With concern for the environment, thermoplastic polymers (TPs) allowed recyclability. However, a drawback is easy CF pull-out from difficult-to-adhere TPs due to insufficient contact sites. Therefore, research on a novel method of homogeneous low voltage electron beam irradiation (HLEBI) to activate a bare CF half-length prior to dipping in a TP resin was reviewed and showed that the UTS by the RM of Ti/ CF/acrylonitrile butadiene styrene (ABS) and Ti/ CF/polycarbonate (PC) joints increased 154% (from 55 to 140 MPa) and 829% (from 30 to 195 MPa), respectively, over the untreated sample. The optimum 0.30 MGy HLEBI prevented CF pull-out by apparently growing crystallites into the TP around the CF circumference, raising the UTS amount closer to that of epoxy.