Hierarchical anisogrid stiffened composite panel subjected to blast loading: Equivalent theory

Hierarchical anisogrid stiffened panels (HASPs) have two-level stiffeners. The primary stiffeners improve the global stiffness of the HASP and the sub-stiffeners enhance the local stiffness of the mono-cell skin supported by the primary stiffeners. A smearing method was proposed to homogenize the HASP into a homogenous panel, based on two-step equivalences of extensional rigidities and bending rigidities. Dynamic responses of blast-loaded HASPs were analyzed based on the homogenous panel and the mode superposition method and validated by finite element (FE) analysis. Commonly the HASP vibrates like a homogenous panel and the theoretical prediction is accurate. Local mono-cell vibration appears only when the skin and the sub-stiffeners are weak enough. The model was applied to analyze the blast response of a composite protective door. Failure criterion based on maximum strain was proposed to predict the peak blast pressure the HASP can bear. The equivalent theory has good accuracy, providing a feasible way to analyze blast responses of HASPs.