BIAXIAL BUCKLING OF THIN LAMINATED COMPOSITE PLATES

Finite element (FE) method is presented for theanalysis of thin rectangular laminated composite platesunder the biaxial action of in – plane compressive loading.The analysis uses the classical laminated plate theory(CLPT) which does not account for shear deformations. Inthis theory it is assumed that the laminate is in a state ofplane stress, the individual lamina is linearly elastic, andthere is perfect bonding between layers. The classicallaminated plate theory (CLPT), which is an extension ofthe classical plate theory (CPT) assumes that normal to themid – surface before deformation remains straight andnormal to the mid – surface after deformation. Therefore,this theory is only adequate for buckling analysis of thinlaminates.A Fortran program has been compiled. New numericalresults are generated for in – plane compressive biaxialbuckling which serve to quantify the effects of laminationscheme, aspect ratio, material anisotropy, fiber orientationof layers, reversed lamination scheme and boundaryconditions.It was found that symmetric laminates are stiffer than theanti – symmetric one due to coupling between bending andstretching which decreases the buckling loads ofsymmetric laminates. The buckling load increases withincreasing aspect ratio, and decreases with increase inmodulus ratio. The buckling load will remain the sameeven when the lamination order is reversed. The bucklingload increases with the mode number but at different ratesdepending on the type of end support. It is also observedthat as the mode number increases, the plate needsadditional support.