The influence of braided structure on bending strength of CFRP pipes with grinding

Golf clubs mainly consist of three parts, namely head, shaft, and grip. It was in the shaft that composite materials are used most. The shaft plays a role of storing up energy during the swing, by way of deforming itself due to bending and twisting moment, and releasing the stored energy at the impact of hitting balls. Shafts can be characteristic in weight, flexural--rigidity, torsional-rigidity, frequency and intensity. Therefore, shafts are considered one of the most suitable sports equipment to apply the excellent characteristics of composite materials to. "Sheet Winding method", using uni-directional (UD) prepreg, is the most widely used process in golf shaft manufacturing. "Braiding method", on the other hand, produces the shafts with three-dimensional braiding structure, using the prepreg with more resin than UD prepreg. This method can only use the limited kinds of carbon fiber. So there is less flexibility in design. However, braided composites are unique and attractive in product line-up, together with their mechanical characters, in comparison with sheet wrapping composites. Braided fabrics are composed of Braided Yarns (BY) oriented diagonally and Middle End Yarns (MEY) inserted into the fabric in longitudinal direction. Therefore it's different in design technique because it's different in the internal structure. Braided composites are unique and attractive with their mechanical character, in comparison with sheet wrapping composites. In this study, the influence on intensity caused by grinding was examined. At first, the influence of amount of grinding in 4point bending test was considered. Next, cantilever bending strength test of golf shaft was performed. And the influence of amount of grinding was clarified about these bending tests.