| Summary: | 碩士 === 中臺科技大學 === 醫學工程暨材料研究所 === 104 === Due to continuing advances in technology, people have higher standard of living, and increasing emphasis on safety, which has led to the fast development of various kinds of shielding equipment. Extreme sports athletes require protective equipment that has high impact resistance. Therefore, this study proposes improving the insufficient impact resistance and lack of monitoring functions of commercially available kneepads.
This study is divided into four stages. In the first stage, highly resilient polyester (HRPET) fiber and low-melting-point polyester (LPET) fiber are blended at different ratios, forming HRPET/LPET nonwoven fabrics. The optimal parameters are then determined based on the mechanical test results. In the second stage, the optimal HRPET/LPET nonwoven fabrics are laminated with woven glass fabrics (WGF), during which the nonwoven fabrics have different basis weights and the lamination angles are changed. The HRPET/LPET/WGF composites are examined for mechanical properties to determining the optimal parameters. In the third stage, two molds of different thickness are used. Vermiculite(Ve) at different sizes is added to flexible polyurethane (PU). A layer of composite is placed in the mold, the PU is added, and another layer of composite is placed onto the PU foam. The HRPET/LPET/WGF/PU composites are made with different thicknesses, and tested for mechanical properties to determine the optimal kneepads. In the fourth stage, an acceleration sensor is combined with this knee pad in order to monitor the impact force and durability. This sensor can link to an APP on a cellular phone, sensing the acceleration rate. When the kneepad loses impact resistance, which leads to an abnormal acceleration, the sensor sends an alarm to the phone which beeps.
The test results indicate that adding an appropriate amount of LPET fiber helps to improve the mechanical properties of the HRPET/LPET nonwoven fabrics as well as the combination of HRPET and LPET fibers. Thermal treatment is used to bond LPET fiber and other fibers, thereby improve the bonding between nonwoven fabrics and WGF. The optimal ratios of HRPET to LPET fibers is 8:2, which results in a tensile strength of 602N and a bursting strength of 477N. The optimal lamination combines three layers of nonwoven fabrics at different basis weights (150, 250, and 350g/m2) with a layer of WGF as 150/250/WGF (0°)/350 composites, which results in a residual stress of 3115N, a bursting strength of 1346N, and a tensile strength of 1069N. In addition, when three layers of nonwoven fabrics and two layers of WGF are combined, the optimal lamination is 150/WGF(0°)/250/WGF(0°)/350 composites, which yields a residual stress of 1232N, a bursting strength of 1560N, and a tear strength of 1020N. Finally, PU foam is added to the composites and the optimal parameters are vermiculite at a particle size of 0.25mm and at an addition of 5%, along with a PU thickness of 10mm. The optimal kneepad is 150/WGF(0°)/VePU/WGF(0°)/250/350 composite, which yields a residual stress of 895N. Combining HRPET/LPET/WGF composites with flexible a PU foam results in extraordinary impact resistance.
The proposed kneepad can has a higher impact resistance than existing extreme sport kneepads. Moreover, the acceleration sensor can detect an excess force or wear on the kneepads, preventing knee injury or pain.
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