Ph.D. (Engg): Numerical Studies on the effect of core metal type and thickness on the mechanical behaviour of fiber metal laminates

Fiber Metal Laminates are materials that combine metal properties with Fiber Reinforced Plastics (FRP) to improve mechanical performance. This research investigates the impact of core metal type and thickness on the tensile and impact behavior of FMLs. Initially two types of FML were modeled: GFML based on GFRP and HFML based on CFRP and GFRP. Numerical simulations were performed to predict FMLs’ behavior under low-velocity impact loading. Results showed that hybridization of CFRP with GFRP increased maximum force but reduced maximum displacement and energy absorption. Studies have shown that GFRP and CFRP layer positioning and thickness along the laminate the can enhance contact force and energy absorption, but enhances the delamination at material interfaces. The importance of optimal stacking sequences is evident as hybridization also causes enhanced delamination. The study also, examined the effect of the core metal layer thickness on low-velocity impact behavior of FMLs. It found that adding a thicker aluminum layer to the middle of the laminate improves energy absorption and reduces permanent displacement due to higher plastic dissipation. Laminates with thicker aluminum cores also show superior impact resistance, making them suitable for impact-prone applications. Initial studies found that the metal layer in the fiber metal laminates plays a dominant role in achieving the desired properties. Hence, the present study focuses on the role of core metal type and its thickness on the tensile, low velocity, and high velocity impact behavior of fiber metal laminates. Aluminum 2024 T3 – GFRP-based FML with a titanium 6Al 4V core layer and Titanium 6Al 4V – GFRP-based FML with an aluminum 2024 T3 core layer are considered to study the effect of the core metal layer and its thickness on the tensile and impact behavior of fiber metal laminates. Tensile simulations were performed for different core metal layers with varying thicknesses ranging from 0.8 mm to 2 mm at the core position of the laminate. The results show that aluminum-based FML with a titanium core improves elastic modulus, yield strength, ultimate tensile strength, and failure strain compared to titanium-based FML with an aluminum core. In addition, the deep neural network has been used to predict the stress-strain curve of FMLs, focusing mainly on the thickness of the core metal. The DNN results closely match the FEA results. In continuation, numerical simulations were carried out to study the effect of the type of core metal and its thickness on the low-velocity impact behavior of fiber metal laminates. The results showed that an increase in the thickness of the titanium core in aluminum-based FMLs reduces the energy absorption capacity and the plastic dissipation energy while increasing the maximum force and displacement ratio. The study shows that titanium as the core layer is recommended when the thickness of the titanium layer is less than the total thickness of the aluminum layer. In addition, numerical simulations were also carried out to evaluate the influence of the core metal type and its thickness on the high-velocity impact behavior of FMLs. The results indicated that the ballistic velocity increases with increasing thickness of the titanium layer. Laminates with thicker titanium layers showed higher impact resistance and energy absorption. This thesis establishes an approach to tailoring FMLs by describing the relationship of fiber hybridization, core metal type, and its thickness to achieve desired FML properties. The findings demonstrate the development of innovative hybrid materials with superior impact resistance, tensile strength, and energy absorption, confirming their suitability for demanding engineering applications.

Speaker: Sadananda Megeri  

Research Supervisor: Narayana Naik G