Integrated Research on Carbon Composite Materials. Volume II. Structural Mechanics.

摘要

Optimization studies (minimum weight design) OF STIFFENED CYLINDERS SIMILAR TO THE FUSELAGE COMPONENT WERE CARRIED OUT BY TWO DIFFERENT TECHNIQUES. The behavior of composite structural elements was investigated in plate-buckling and post- buckling studies, buckling of stiffened plates with cutouts, and application of shell theory to anisotropic cylinders. Micromechanics studies of fibrous composites included development of a photoelastic technique for analyzing frozen stresses, a discrete element microstress analysis of unidirectional fiber composites, an application of the theory of physically nonlinear elastic solids to composite materials, and an investigation of the multiple circular inclusion problem in plane elastostatics. Failure of composite structural elements was investigated through studies of the failure mechanism for off- axis composites, the fracture toughness of composites, the effect of fatigue and sustained loads of cross-plied composites, the notch sensitivity of cross-plied composites, and the effect of a variety of known intentionally interjected defects on the fracture strength. Multiaxial stress testing of composite cylinders was included. The effects of circular and square cutouts in flat panels and in a stiffened panel, and methods of reinforcement of cutouts were investigated and correlated with predications based on discrete element analysis. (Author-PL)