Potential of composites with integrated shear thickenning fluids as tuneble damping layer in skis
Tutor / director / avaluadorNeagu, Cristian
Tipus de documentProjecte/Treball Final de Carrera
Condicions d'accésAccés restringit per acord de confidencialitat
Reducing vibrations of sports equipment has recently become of great concern in the sports engineering industry. There has also been a recent interest in better understanding and improving the interplay between the sports equipment properties and the reception of the athlete using the equipment. The aim of this thesis is to show the potential of composites with integrated shear thickening fluids (STFs) as tuneable damping layers in jumping skis to tailor both stiffness and damping. The main goal is to eliminate the first vibration mode of jumping skis during the early flight of the jump. During the first project phase, the regulations for the ski jumping and the actual damping systems being used were identified. Then, the structure and behaviour of jumping skis were analysed. For this purpose, a jumping ski was cut and some of its structural materials were characterised. A three point bending test and several vibration tests were done to a pair of jumping skis to determine the bending rigidity and the vibration behaviour. During the second phase of the project, a methodology of working for integrating STFs into high amplitude and low frequency vibrating structures was presented. Several integration ideas were firstly explained and analysed. A finite element model was built to obtain the optimal placement of the damping systems. Damping layers which contain STF coated rods in a compliant matrix were designed, manufactured and integrated into several jumping skis. A total of nine skis were modified and tested to compare their new properties. One of the integrated damping systems, where the STF is contained in between a thin exterior plate placed on top of the ski and clamped at the binding while allowed to move freely at the other, showed very promising results. The damping of the modified ski was increased by 36.1% for the first vibration frequency and by 103.1% for the second vibration frequency. The other damping designs did not show relevant improvement on damping. The shear strain at the rodmatrix interface was not enough to activate the integrated STF and the volume of STFs was probably too small to absorb all the vibration energy of the ski. Nevertheless, the methodology presented in this work will allow optimisations of systems with integrated damping layers, where the STF is contained at the interface between a stiff rod and a compliant matrix. However the tremendous challenge of finding solutions for manufacturing damping layers with integrated STFs beyond the laboratory scale still remains. In summary, this thesis has provided a method to design and place composites with integrated shear thickening fluids into vibrating structures to act as damping layers.
MatèriesSkiing equipment industry, Vibration, Esquí Equip i accessoris, Amortiment (Mecànica), Vibració
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