Co-authors​ :

 Muzafar HUSSAIN (UNITED ARAB EMIRATES), Wael ZAKI , Wesley.J. CANTWELL , Muhammad Yasir KHALID (UNITED ARAB EMIRATES), Rehan UMER (UNITED ARAB EMIRATES) 

The demand for lightweight materials and structures coupled with functional characteristics has led to the development of different material systems, one such class of these materials are the shape memory alloys (SMAs). Fiber Metal Laminates (FMLs) are widely used in aerospace industry for enhanced mechanical performance and light-weighting of structures. Several mechanical and electrochemical surface treatment processes such as etching, sandblasting, and anodization etc., are usually carried out in order to enhance the adhesion between the metal surface and the polymer matrix of the FML. In this study, the mechanical properties of NiTi-based smart FMLs are explored. Prior to manufacturing, NiTi sheets were anodized using different surface treatment methods. The wettability of NiTi sheet surfaces after treatment was also analyzed using the contact angle measurements using a goniometer implementing sessile drop method. The anodized surfaces were fully characterized using an SEM to visualize the morphology of the metal surfaces after anodization. The Vacuum Assisted Resin Transfer Molding (VARTM) process was used to manufacture Glass fiber/NiTi FMLs by drilling an array of holes within the NiTi sheets to facilitate through thickness resin flow.
Figure 1(a) shows the experimental setup through which anodization of NiTi sheets was carried out, where NiTi sheets were used as anode. The H2SO4 and HNO3 solutions were used in different concentrations with different applied voltages and currents to investigate the effect of several process parameters on the morphology and wettability of NiTi sheets. Figure 1(b) shows the morphology of the NiTi sheets after being anodized, where fully developed pores are evident on the surface of NiTi. It was also noticed that the morphology of porous surface was highly dependent on the process parameters selected. Figure 1(c) shows the view from the bottom of infusion table while FML was being manufactured using the VARTM process. It can be seen from Figure 1(c) that the holes facilitated the flow of resin through the thickness of the glass fabrics during infusion. Moreover, Graphene Nano-platelets (GNPs) were added to the resin to enhance multifunctional properties and promote adhesion. Finally, several mechanical tests were conducted as per the ASTM standards. It was concluded that anodization, along with adding only a small amount (0.1 wt%) of GNPs in the resin had a positive effect on adhesion and the mechanical performance of the NiTi-based FMLs.