| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 101 === The face/core interfacial crack behavior of the sandwich beams with glass/polypropylene faces and aluminum foam cores was experimentally studied in this thesis using mixed-Mode bending (MMB) method. The effects of the mixed Mode at the crack tips and the core heights on the critical loads and the critical strain energy release rates at the interfaces of the studied sandwich structures under the static loading were investigated first. The mixed Mode at the crack tips can be adjusted by changing the length of level arm of the MMB configuration. The finite element method was employed to determine the Mode-mixity at the crack tips, which was expressed using the phase angles. Secondly, the relationship between the crack propagation rate and the range of strain energy release rate for the studied pre-cracked sandwich beams was experimentally determined. The effects of the mixed Mode at the crack tips and the core heights on the crack propagation rates were also studied. In this study, the beam theory was used to obtain the compliance of the pre-cracked specimen under MMB, and correspondingly the strain energy release rate can be determined. Experimental results show that in the static tests, the critical loads and the critical strain energy release rates decrease as the phase angles at the crack tips of the studied specimens increase. In the fatigue tests, the crack propagation rate of the sandwich specimen with thinner core height is less than that with thicker core height. Furthermore, the ratios of the tensile Mode to the shear Mode at the crack tips have slight effect on the crack growth rates of the studied sandwich specimens.
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