新型夾具應用於複材單疊混合接頭之機械性能探討

• Main Authors: WEI-HWANG LIN, 林偉煌
• Other Authors: MING-HWA JEN
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/26381210784060243280

博士 === 國立中山大學 === 機械工程學系 === 88 === This research is concerned on the investigation of mechanical properties by tension fracture and fatigue for mixed joints made of composite materials by adopting innovative grips designed on the single-lapped tension theory. The result has been later compared with that by using the conventional grips in addition to a corrected end tabs. It is known that the tension or fatigue test of a single-lapped joint causes a specimen not self-collinear. A conventional correction is adopted to solve this problem by using end tabs of suitable thickness or rebinding the specimen after it is slightly inclined. Therefore, the actual load is much different from the theoretical load. Further, the tension of a single-lapped joint must keep both end centers of the specimen collinear with its lap center. This can not be succeeded the conventional method. However, the innovative grips can achieve this goal and obtain more precise and reliable results than those by the conventional method. Sixteen-layer laminates of graphite/epoxy were used as adherends, including cross-ply and quasi-isotropic laminates. After drilling a hole in the center of overlap, we inserted a bolt or a rivet with adhesive at the interface to form a rigid mixed joint. Our main work was experiments, such as tensile test and tension-tension fatigue test at stress ratio=0.1 and frequency=5 Hz, the environmental effects of moisture and temperature were neglected. The mechanical properties of mixed joints, obtained by both conventional MTS grips and new model grips, were compared and the real strength and life of mixed joint would be clarified. From the parametric study systematically we can achieve the important results as follows. No matter what grips were used, the fracture strength and fatigue strength of cross-ply joint are larger those of quasi-isotropic joint. Comparing mixed joint with single-lapped joint, we find that the tensile strength of mixed joint is lower, but its fatigue strength is lager. In mixed joints, the bolted & bonded joint is always stronger than the riveted & bonded joint due to the mechanical fastening. In the consideration of clamping force, the mixed joint with more clamping pressure will possess higher resistance to fatigue and fracture. Similarly, any mixed joint with longer overlap will become stronger no matter what grips used. However, the mixed joint will approach a constant value of strength asymptotically with the increase of overlap. Generally speaking, both strengths of fatigue and fracture obtained by using new model grips is lower about 10% than those by MTS grips. Hence, we overestimate the strength about 10% by using traditional grips for a long time. That provides an important reference for design and application. And a rotatable rivet is provided. This rotatable rivet contains inner threads in order to prevent the shank and the socket of rivet from breakaway. Therefore intensifying the binding stress of the working pieces and improving the working safety.