Optimum Design and Validation of a Graphite Golf Shaft Based on Dynamics of Swing.

A player΄s swing motion is analyzed and the head speed is assumed as a cubic function. Then, swing accelerations and forces acting on a sweet spot of a club head are calculated. Under these forces, the deflections and twists of a shaft with optimum stacking sequences are analyzed right before the impact and at the instant of impact. An efficient optimization algorithm is introduced to optimize the stacking sequence of the shaft and wall thickness that satisfy the strength, weight, flex ratings, a kick point and dynamic torsional flexion using a genetic algorithm and finite element analyses. Unlike steel, the shaft made of graphite/epoxy materials shows many different static and dynamic behaviors during swing, depending on its ply orientations. The cost function is a minimum twist of a composite club shaft and seeks the stacking sequence satisfying flex, kick point and weight requirements. After iterative 28 generations, the optimal stacking sequence for the minimum angle of twist is obtained as [30/45/–30/0/–45]_s and results in the twisting angle of 1.1°. Before the impact, the maximum deflection is 22.6 mm and the largest twist is 0.121°. At the impact, the maximum deflection is −168.991 mm and the largest twist is 0.217°. [ABSTRACT FROM AUTHOR]