Studies of Advanced and Composite Structures

This final report summarizes the objectives and accomplishments of the three tasks pursued during a one-year grant from AFOSR to continue ongoing research in development of new bending and buckling therories for beams and plates, oriented toward composite structures, experimental investigation of the effects of delamination on structural response of composite panels, and damage tolerance of isogrid composite structure, a stiffening concept that employs a repetitive equilateral triangular pattern of ribs. Papers, reports, and presentations resulting from this research are listed. In Task 1 a new theory of bending is developed including effects of transverse shear strain, transverse normal strain, and section warping. Included are a dynamic theory for planar bending of homogeneous beams, static theory for homogeneous plates, buckling theory for homogeneous columns, planar bending theory of composite laminates, theory for laminated plates, and a theory for bending and buckling of stiffened plates. Task 2 investigates structural consequences of delamination using a series of quasi-isotropic symmetric ply layup composite panels with single delaminated zones between the central plies, all delaminations of the same size (ten percent of the panel area) but all of different shapes.