Book Description

An experimental and analytical investigation was conducted on the buckling and postbuckling behavior of laminated graphite/epoxy plates with ply dropoffs under uniaxial compression. Three types of plates were considered: ply dropoff plates with one or more internal plies terminated along a centerline perpendicular to the loading, flat plates to provide the baseline behavior, and angle change plates where the fiber angle of several plies changes abruptly along the centerline. This latter case isolates the change in material properties without the geometric eccentricities present in ply dropoff plates. An analysis method using a "superelement" formulated with a Rayleigh-Ritz assumed deflection model was developed and utilized to predict the linear buckling response of the plates. Both the experimental and analytical results show that ply dropoffs have a marked effect on plate buckling and postbuckling behavior. In contrast to basic flat plates, plates with ply dropoffs exhibit complex deflection shapes that cannot be characterized by simple modes. The buckling load of these plates was related to the ratio of the longitudinal bending stiffness of the dropped and undropped section of the plates and was bounded by the buckling loads of the flat plates with the layup configurations of the two individual sections. The angle change plates exhibited much of the same behavior seen in the ply dropoff plates but indicated that the change in the other bending stiffnesses can also have an important effect on the buckling behavior.