Experimental Results for Bending and Buckling of Rectangular Orthotropic Fiber-Reinforced Plastic Plate Structures

Solid unstiffened, sandwich, and hat-stiffened rectangular orthotropic fiber-reinforced plastic (FRP) plates were tested in uniaxial in-plane compression and out-of-plane uniform pressure. The two short edges of all plates were clamped, whereas the two long edges of the unstiffened and sandwich plates were simply supported and the same edges of the hat-stiffened plate were left free. Unstiffened plates reached global buckling at about 688 kN (155 klb); however, the plates did not collapse up to the machine load limit of 1334 kN (300 klb). Sandwich plates never reached the overall elastic buckling load; they collapsed in local buckling byface sheet delamination and core shear failure at loads of about 939 kN (211 klb). Hat-stiffened plates exhibited local buckling of the outer unsupported flanges at a load of about 356 kN (80 klb). All hatstiffened plates collapsed under uniaxial compression due to a combination efface sheet to stiffener delamination followed by hat-stiffener local buckling at loads of about 939 kN (211 klb). The stresses and deflections due to out-of-plane uniform pressure were compared between the unstiffened, sandwich, and hatstiffened plates from pressures of 6.895 kPa (1 psi) to 34 kPa (5 psi). With the plates under uniaxial compression and out-of-plane uniform pressure simultaneously, there was a general decrease in buckling and collapse with an increase in out-of-plane uniform pressure.