Influence of UHMWPE fiber and Ti6Al4V metal surface treatments on the low-velocity impact behavior of thermoplastic fiber metal laminates

The unique combination of alternate thin layers of metal and complete thermoplastic fiber-reinforced polymer (FRP) gives birth to a new generation of hybrid thermoplastic fiber metal laminates (T-FML), which are considered for high impact resistance applications. T-FML is fabricated by Ti6Al4V metal alloy and ultra-high molecular weight polyethylene (UHMWPE) with infusible liquid methyl methacrylate thermoplastic resin (Elium®). The impact damage resistance of T-FML depends on the interlaminar interface and metal thermoplastic composite interface (MTCI). Higher interfacial properties provide improved stiffness and resistance to the delamination of crack growth in T-FML during an impact loading. Fiber and metal surfaces are modified to enhance the interlaminar interface and MTCI. The fiber surface is treated by a simple deposition of polydopamine (PDA) with the addition of 0.03 wt.% multiwalled carbon nanotubes (MWCNT), and the metal surface is treated by using an electrochemical process. Experimental investigations were carried out on the T-FML composite laminates to determine the low-velocity impact behavior at three different impact energies (43 J, 50 J, 80 J). The results revealed that the non-impacted Ti alloy face sheet on the rear side of the T-FML plays an important role in absorbing the impact energy by creating a single crack in the rolling direction. Also, the single crack growth is suppressed when the MTCI is improved after the fiber and metal surface treatment.