Theoretical and Numerical Analyses in Hybrid Ti/APC-2 Composite Laminates Due to High Velocity Impact

Abstract

Fiber/metal composites (FMCs) have attracted much attention over twenty years, especially in the applications to aerospace and aeromechanical structures. In addition to their advantages of fiber reinforced composites they also possess superior resistance to cyclic loadings. It is well-known known that conventionally the composite laminates are weak due to out-of-plane loads. Hence, vulnerability against high velocity impact loads is becoming an increasingly critical issue for the design of FMCs in aerospace structures recently. In this study we mainly focus on the theoretical derivations of penetration and perforation in Ti/APC-2 hybrid composite laminates impacted by a hemispherenose cylindrical projectile at high velocities, and verifies the results by numerical simulation, such as finite element method and ANSYS LS DYNA 3D software.Fundamentally, cross-ply [0/90]4s and quasi-isotropic [0/±45/90]2S APC-2 composite laminates are investigated. Then, Ti/APC-2 hybrid laminates are studied as an extensional work based on previous experience. It is quite different from the cases of low velocity impact that the boundary conditions and geometry of laminated plate can be omitted, and the wave propagation model should be used in high velocity impact. Thus, a rectangular composite laminate is analyzed for general purposes. The theoretical process involves first the deformation and failure of face sheets, through-thickness propagation of shock wave into the middle plies of shear failure, fracture of back sheets and perforation finally. Equations of motion for the projectile and effective masses of the face sheets, middle plies and back sheets as shock wave traveling through the whole laminate are derived by using Lagrangian mechanics. The analytical approach is mechanistic involving no detail account of progressive damage due to cracking, delamination and debonding, etc.Analytical predictions of total time of traveling ballistic limit, (perforation of laminate with zero residual velocity), residual velocity, transient deflection and velocities of projectile are determined. They are compared with the results from numerical simulation within acceptable errors. Both methods provide valuable achievements that makes us thoroughly understand the phenomena of high velocity impact in composite laminates.