フィラメント・ワインディング・パイプの静的および疲れ曲げ強度

This paper presents the results of analysis and tests conducted on the static bending strength of carbon fiber filament-wound (F.W.) cylindrical pipes and also the results of tests on fatigue flexural strength of the same F.W. pipes. The relation between the winding angles of F.W. pipes and their fracture strengths under pure bending is investigated. The analytical method of the fracture strength of F.W. pipe is as follows; the threedimensional stress components referring to the plane including fibers are analysed, taking account of the elastic failure prior to the overall fracture and then are compared with the fundamental strengths corresponding to the four kinds of fracture mechanisms of unidirectional fiber reinforced composites. As the results of the analysis, the fracture modes under pure bending of the helical winding pipe are determined in relation to its winding angle; 1) Winding angle α=0°∼10°, Fracture caused by compression stress in the fiber direction. 2) Winding angle α=15°∼30°, Fracture caused by tensile stress normal to fibers. 3) Winding angle α=35°∼50°, Fracture caused by shear stress. 4) Winding angle α=55°∼90°, Fracture caused by tensile stress normal to fibers. The static and fatigue flexural tests are done on carbon fiber F.W. pipes in which helical winding angles are α=15°, 25°, 35°, 45°. By using a newly-devised chuck, the fatigue test of the F.W. cylindrical pipe was carried out successfully. The bending fracture test results on the fracture strength and fracture modes coincide with the analytical ones. The flexural fatigue test results which showed that the ratio of the flexural fatigue strength at 107 cycles to the static bending strength are about 0.3 for the helical winding angle α=15°, 25°, and about 0.2 for α=35°, 45°.