Parametric study on factors influencing the stiffness of honeycomb sandwich panels using impulse excitation technique

Metallic thermal protection systems are used to protect the airframe and pay load from aerodynamic and aerothermal heating in hypersonic cruise vehicles that are powered with advanced scramjet engines. Metallic thermal protection systems is a composite structure that contains honeycomb sandwich panels at the top and bottom and a variety of thermal insulating materials placed in between them. Several design factors influence the structural and thermal performance of the honeycomb sandwich panels. Panel bending stiffness is one important structural property that is generally estimated using a destructive 3-point or 4-point bending test. In this study, a numerical model based on the impulse excitation nondestructive evaluation technique has been developed to estimate the effect of various design parameters that affect the bending stiffness of the honeycomb sandwich panels. The results obtained are analyzed using standard statistical procedures. A major advantage of this method lies in evaluating the panel stiffness at the design stage without resorting to actual fabrication of the panels for destructive testing.