The Responses of Pultruded GFRP Sandwich Panels Filled With EPS Mortar Under Explosions in Succession: Testing and Analyzing

This study experimentally and theoretically investigates the dynamic response and damage characteristics of pultruded GFRP sandwich panels filled with EPS mortar under sequential blast loads. The pultruded GFRP sandwich panel consists of upper/lower 4 mm‐thick skins, a 3.5 mm middle web and seven internal hollow chambers. Two types of EPS mortar with densities of 255 and 460 kg/m 3 were adopted as core fillers, denoted as EGP1 and EGP2, respectively. Dynamic strain and displacement responses, and failure modes of the panels were recorded and analyzed, and a theoretical model based on the first‐order shear deformation theory was established to predict the dynamic response. The results show that the density of EPS mortar significantly affects the blast resistance of the panels. Compared with EGP1, EGP2 exhibits lower peak strain, smaller maximum displacement, and less damage under the same blast loads, presenting better bending resistance and shear strength. Both panels present obvious mechanical anisotropy, with longitudinal strain along the fiber direction much higher than transverse strain, induced by nearly cylindrical bending deformation. The simplified beam model based on the modal superposition method can effectively predict the peak displacement of the panels in the elastic range, and the theoretical results are in good agreement with the test data. The research provides a reliable reference for the protective design of EPS mortar‐filled GFRP sandwich panels under blast loads.