Analysis of circular fiber metal laminate plates with curvilinear fiber under low velocity impact loading

In the present study, the behavior of circular plate made of fiber-metal laminates with curvilinear fiber subjected to low velocity impact is investigated using an analytical method. The composite layers are made of glass-epoxy that placed between two layers of Aluminum 2024-T3. Differential equations of motion are formulated using the spring-mass model and appropriate initial conditions for loading and unloading stages. The deformation of aluminum were idealized as rigid-perfectly plastic and the composite layers as linear elastic. Using the principle of minimum total potential energy, applying the Von Karman strain and by neglecting the contribution of the in-plane displacements and bending strain energy, the nonlinear relationship between the contact force and deflection is derived. Also, a method for calculating the average stiffness of the plate is developed and employed to estimate the internal damage due to delamination. The effect of the layup and geometric parameters of the plate and the impactor on the plate response is investigated. Different functions are examined to describe the shape of the deformed plate under loading and the results are compared with the experimental data for validation purpose. Furthermore, an investigation of the possible performance improvements of a composite plate under impact loading through the use of the variable stiffness concept with curvilinear fiber is presented. The analytical results indicate the alteration in load paths and favorable stress distributions within the variable stiffness laminates. However, the maximum deflection and the contact force of variable stiffness laminates are similar to the conventional, constant stiffness ones.