Comparison of the static and dynamic behaviour of carbon fibre composite golf club shafts

Golf shafts are characterized and sold by manufacturers on the basis of their static properties; however, their performance is controlled by their dynamic proper-ties. This paper discusses the relationship between dynamic and static stiffness for a range of carbon fibre composite (CFC) shafts. In particular, the influence of 'seams' (specific orientations of the shaft with differing mechanical proper-ties) on static and dynamic stiffness is considered. Vibrational frequency analysis (quasi-static testing) was used to locate the seams, and bend testing was used to determine the static stiffness of the low (seam) stiffness and high (90 degrees to seam) stiffness positions. Dynamic stiffness values were determined by firing a golf ball from a gas cannon at a target attached to the end of the shaft and measuring the resulting deflection for different golf ball speeds. It was found that the dynamic stiffness values over a range of strain rates were similar to the static values for the sheet-laminated shafts indicating that there is no strain rate dependency for these shafts over the strain rates tested. However, for the filament wound shaft, a significant increase in dynamic stiffness, compared with the static value, was seen. This was related to the different CFC microstructure of this shaft. It was also found that the presence of seams resulted in statistically significant differences in static stiffness with respect to shaft orientation for a number of sheet-laminated shafts, whereas there was no difference in dynamic stiffness values.