Composite materials offer significant improvements in fatigue behavior, impact performance and damping coupled with high stiffness and strength. Due to these properties and an increasing demand for high performance cutting-edge sports equipment, more scientific and engineering research is now being focused in the field of recreation. The use of stiff, lightweight composite materials has created many novel features in golf clubs, baseball bats and skis; features generally not possible with conventional materials. The performance, user comfort, and fatigue life of these products are strongly related to their dynamic characteristics. Design decisions relevant to these issues should, therefore, be made based on an understanding of the dynamic characteristics through modal parametric studies.
This paper discusses the vibration response characteristics of some commercially available hockey sticks with wooden, aluminum and graphite shafts, when subjected to short duration impact loads. Using an instrumented impact hammer, a complete modal survey is initially conducted on these hockey sticks to study their dynamic behavior. A comparative study of the modal parameters (natural frequency, damping, and mode shapes) of the different hockey sticks provides valuable information for design optimization and to validate the accuracy of a finite element model. In addition, a refined two-accelerometer technique has been utilized to perform vibrational energy level tests (on the blade portion of the hockey sticks) to obtain the flexural and torsional vibration level distribution and to map out the sweet spot locations. Results indicate that this combined strategy of using both approaches provides a better understanding of the vibration performance characteristics of hockey sticks. Work is currently in progress to extend this technique for characterizing golf clubs.