Parametric instabilities of variable angle tow composite laminate under axial compression

Dynamic instability of a variable angle tow (VAT) composite plate subjected to periodic in-plane compressive load is investigated using finite element analysis. First order shear deformation theory was used to model the VAT laminate and the effect of fiber angle orientation on the instability behavior of VAT laminates is studied. Unlike straight fiber composites, the pre-buckling problem of VAT laminate is solved initially to obtain the plate in-plane stress distribution due to the applied uniform compression along the edges. Subsequently, the evaluated stress distributions were used in the equations governing the dynamic instability of VAT laminates. The dynamic instability regions of VAT laminates are determined using Bolotin's first order approximation. The dynamic instability results of VAT plates are evaluated for linear fiber angle distribution and their performances are then compared with straight fiber laminates. Effect of the fiber angle orientation, load parameters, boundary conditions, orthotropy ratio and aspect ratio on the dynamic instability regions of VAT laminate are investigated in detail.