Parametric Study of Surface Imperfections and Small Cutouts in a Composite Panel

摘要

A finite element computer code, STAGS C-1, was used to study the effects surface imperfections and cutouts have on the load bearing capability and the displacement patterns of a graphite-epoxy panel. A nonlinear collapse analysis was conducted on two different ply layups each with five different surface imperfection patterns. In addition three different ply orientations were studied each having two different size cutouts (a two inch by two inch square and a four inch by four inch square). The nonlinear branch of STAGS C-1 uses a energy technique using the nonlinear stiffness matrix that was generated by using the Sanders' strain displacement equations. STAGS did a very good job in calculating the collapse load and displacement of a panel with surface imperfections when compared with experimentally tested panel. The collapse characteristics of composite panels are dependent on the ply layup and size of the cutout. Small cutouts had a displacement pattern that was not expected and is different than the larger cutouts. Changing the vertical boundary conditions on the panel with the small cutout had a negligible effect.