| Summary: | 碩士 === 國立雲林科技大學 === 機械工程系 === 106 === With the development of various lightweight materials in automotive industry, the carbon fibre composites have gradually become essential. The carbon fibre composites will slowly replace those light metal alloys in automotive body structure and crumple area. This is because these carbon fibre composites are able to reach the material lightness without reducing the strength. When a car is under an impact in a collision, it is important to increase the absorbed energy. Therefore, it has to have a quality of stable collapse in a crash impact in order to optimize the energy absorption.
This study focuses on the impact test of the carbon fibre composite circular tube. In addition, a polyethylene (PE) foaming material was added into the tube in order to increase the ability for absorbing energy. To characterize the impact behavior, the peak force, the crumple distance, the energy absorption, the specific energy absorption, and the fracture mode are discussed. Two types of tubes with 75mm diameter were used in this research. One was empty tube and the other one was filled with PE foam which will be termed as 75mm empty tube and 75 mm PE tube. For the impact test, the energy was setting to 393 joules and 430 joules. In addition, finite element analysis by LS-DYNA was used to simulate the entire process of the impact. Both the simulation and experiment results were then compared. From the experiment, the results indicate that under the impact energy of 393 joules, the crumple distance of the 75mm PE tube was 0.63mm that is less than that of the 75mm empty tube. The energy absorption is better for the 75mm PE tube. However, this improvement is not good enough. The energy absorption only raises 2.73 joules and the SEA value increases 0.72 (J/g). By raising the energy to 430 joules, the crumple distance of the 75mm PE tube is 1.31mm that is still less than that of the 75mm empty tube. Even though the energy absorption is improved, the effect is not distinguished. The energy absorption only raises 2.05 joules and the SEA value increases 1.42 (J/g). The simulation data is close to the experimental results with the error less than 7%. This shows the reliability of this research.
To summarize the result of experiment and simulation, the 75mm PE tube can raise the energy absorption property and SEA value, but the effect is limited. Furthermore, the result of the fracture mode is not consistent between the simulation figures and experimental results. The simulation fracture mode shows only a radial shape, but the experiment fracture mode shows both the radial shape and the horizontal fracture.
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