Tennis racket shock mitigation experiments

Measured in this study was the effectiveness of two types of retrofits in mitigating shocks in tennis rackets with ideally high grip fixity. The retrofits were a cushioned grip tape and a string implant device. Three types of rackets were investigated: wood, graphite composite, and metal. For low speed ball impact, neither retrofit changed significantly the magnitude and distribution of e, the coefficient of restitution on the racket heads. For moderate ball speeds impacting the rackets along the vertical centerline, three dynamic racket responses were measured: the free vibration damping based on racket head acceleration, the root-mean-square (rms) grip reaction force, and the fast Fourier transform (FFT) of the grip force. These latter experiments showed that the string implant device had a negligible effect on the three dynamic measures of racket response. However, the cushioned grip tape increased racket damping by up to 100 percent, reduced the rms grip force by about 20 percent, and reduced the magnitude of the FFT of this force by about 40 percent.