GFRP Stiffened Plate with Square Cutout under Axial and Out-of-Plane Load

The high-strength-to-weight ratio and corrosion resistance properties of glass-fiber-reinforced polymer (GFRP) composites makes them potentially well-suited for application in ship structures, bridges and off-shore oil platforms. These structures are often formed by stiffened plates and are subjected to axial load and out-of-plane load. Cutouts and openings are provided in the plates for access and maintenance. The main objective of this study was to examine the buckling behavior of GFRP-stiffened composite plates with square cutouts under a combination of axial and out-of-plane load up to failure. Four blade-stiffened composite plates without a cutout and four with square cutout were fabricated with stiffeners as a continuous layup of the flange plate using glass fiber and epoxy resin. The initial geometric imperfections were measured, and plate imperfections (Δx), stiffener imperfections (Δsy) and overall imperfections (Δsx) were calculated from the measurements. All fabricated-stiffened composite plates were tested up to failure. The finite element model was developed in ANSYS software and validated with the experimental results. It was observed that GFRP-stiffened composite plates failed by stiffener compression/stiffener tension mode of failure. The presence of out-of-plane loads and cutouts reduced the axial load carrying capacity of the stiffened composite plates.