| Summary: | 碩士 === 逢甲大學 === 紡織工程學系 === 87 === This work examines fabrication and damage behavior of 3D woven carbon/epoxy composites. The major goal was to study the influence of surface loops on their elastic and damage behavior. The results indicate that surface loops almost entirely dictate damage configuration of the materials.
The material characterization includes 3-point bending, compression, and impact tests. With loops, it is found that the flexural strength, compressive strength, and the absorbed impact energy are higher than the non-looped counterparts. When under compression, the most notable mechanism of failure is kink band, forming many V-shaped bands of fiber kinking. When subjected to flexure load, kink bands are also found on the top surface, while fibers break on the bottom surface due to tensile failure. Kinking in the 3D composites can be categorized into two groups: bounded kink and unbounded kink, according to their locations.
3D composites are known to provide multi-directional properties. The surface loops are therefore a necessary part of the fabrics. It was found that surface loops can effectively protect the axial yarns that lie inside the loops. Results reveal that all yarn kinking occurs at locations without the protection of loops. Second, when a crack advances, it avoids the loops which are stronger and circumvents to grow along other directions.
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