On the metal thermoplastic composite interface of Ti alloy/UHMWPE-Elium® laminates

Abstract

Thermoplastic fiber metal laminate (T-FML) is a new hybrid composite material, which is a combination of sandwiched metal and complete thermoplastic fiber reinforced polymer (FRP). Due to its superior properties contributed from the unique combination of metal and FRP's, it has been applied in various advanced fields, like aerospace, and automotive. However, poor adhesion between inhomogeneous material surfaces of fiber, metal, and matrix in T-FML makes the whole system weaker. In this work, the Ti6Al4V (titanium alloy) and ultrahigh molecular weight polyethylene fiber (UHMWPE) reinforced thermoplastic (Elium®) polymeric composite were combined together to form a T-FML. Fiber surface functionalization by PDA (polydopamine) coating with MWCNT (Multiwalled carbon nanotubes) has been adopted to enhance the bonding between the fiber and matrix. Ti6Al4V metal surface treatment by anodization with postprocessing of etching and annealing process has been adopted to enhance the interfacial bonding between metal thermoplastic composite interface (MTCI). The double cantilever beam test was utilized to evaluate the G1C (Mode I interlaminar fracture toughness at MTCI) for the T-FML sample with fiber surface functionalization and metal surface treatment. The result shows, after metal surface treatment, the average G1C can be immediately increased from 0.25 kJ/m2 (pristine titanium alloy with pristine fiber) to 1.57 kJ/m2 for surface-treated titanium alloy with pristine fiber. The PDA only coating for UHMWPE fiber enhanced the G1C from 1.57 kJ/m2 to 1.84 kJ/m2. PDA fiber surface functionalization with MWCNT coating enhanced the G1C further to 2.54 kJ/m2.