LOW-VELOCITY IMPACT RESPONSE OF FOAM-CORE SANDWICH COMPOSITES

The low-velocity impact response of foam-core sandwich composites with fiberglass/epoxy face sheets is treated by a combination of computational and experimental methods. Linear elastic constitutive models are used for the face sheets and epoxy bond layer in conjunction with a foam constitutive model that includes nonlinear hardening plasticity and coupling between volumetric and deviatoric deformation. A transient finite-element code, utilizing four-noded uniform strain quadrilaterals, is used to explicitly solve the equations for balance of mass and momentum. The resulting deformation histories are compared to the experimental results and show qualitative agreement. The computed transverse shear stresses are used to correlate ultrasonic measurement of damage in the core/epoxy interface. Comparison of the plate stiffness prior to and after impact illustrates the effect of damage on subsequent behavior.