| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 96 === It is observed that in most mode II fracture toughness testings, it always exists shearing stress and tensile stress at the same time and causes mixed fracture of mode I-II. In order to obtain a pure mode II fracture, this study proposes a shear-box test to measure the mode II fracture toughness of gypsum. A compressive stress is applied to restrain tensile stress at the notch tips of the specimen. Both the effects of notch lengths for double-notched specimens and the loading inclination angle of the testing fixture have been investigated. The results show that when the fracture-width ratio is 0.5 and the loading inclination angle is 70°, a stable condition for the mode II fracture toughness can be obtained from the shear-box test of double-notched specimen. The shear-box test of double-notched adhesive gypsum specimen has been studied. Three adhesives including Epoxy(1:1), Epoxy(3:1) and Unsaturated Polyester Resin(POLY), are used in the test. The shear strength of the adhesive surface of the specimen is measured. The study also utilizes a finite element program, ANSYS, to evaluate the corresponding stress intensity factors. The results show that the adhesive shear strength of Epoxy(1:1) are better than those of Epoxy(3:1) and Unsaturated Polyester Resin(POLY).
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