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 blastloaded 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.