Buckling and postbuckling response of hybrid composite plates under uniaxial compressive loading

In this study, experimental and numerical investigations of buckling and postbuckling responses of square symmetric plates configured with innovative layup sequences have been conducted under uniaxial compressive loading. Effect of stacking sequences and orientation of fibers on buckling and postbuckling responses of fiber reinforced polymer (FRP) plates made of unidirectional carbon and glass fibers are investigated. Initially, plates with fiber aligned in (0/90) directions are fabricated and tested under uniaxial compressive loading, with simply supported boundary conditions. Later, the plates are modeled and analyzed with FEM based software ABAQUS, and a parametric study is performed with various fiber orientations. The plates considered are plain CFRP, plain GFRP, functionally graded hybrid (FH) and sandwich hybrid (SH). Amongst the stacking sequences, such as (0/90)4s, (-45/+45)4s, and (-45/+45/0/90)2s, the functionally graded hybrid (FH) plate with fiber stacked in (-45/+45/0/90)2s directions showed highest buckling and postbuckling strengths. First ply failure was predicted by incorporating the Tsai-hill failure criterion in the numerical analysis. It is observed that plates with glass fibers in the core region have high strength, and the strength significantly depends on the type of plate and fiber orientation. This type of strength enhancement has been observed in all the plate types, i.e., functionally graded hybrid and sandwich hybrid plates. It is further observed that the numerically investigated results are in good agreement with experimentally obtained values. Buckling and postbuckling responses are also investigated for functionally graded hybrid plates with various shaped and sized cutouts, using similar loading and boundary conditions. Circular, diamond, horizontal ellipse, vertical ellipse, and square shaped cutouts were considered in three different sizes (small, medium, and large). It is observed that plates with a smaller size elliptical shaped cutout aligned horizontally and located at the center of the plate have highest buckling, first failure, and ultimate failure loads.