| Summary: | 碩士 === 逢甲大學 === 紡織工程所 === 95 === In this study, the composite sandwich panels are stitched with Kevlar yarn. Skins of these sandwich structures are plain glass fabrics and the core is polyurethane foam. These sandwich panels are molded by hand lay-up methods and cooperated with vacuum bagging process. The flexural properties, impact behaviors and compression after impact properties of stitched sandwich structures are studied. The effects of the stitched parameters in this study such as stitch spacing, stitch density and linear density of stitch yarn on the relevant mechanical properties as described above are investigated and compared with unstitched structure.
Results show that, the flexural properties of composite sandwich panels are increase with stitch spacing reducing. Compared to the unstitched sandwich panels, the flexural strength of stitched structures are increased up to 23 % in the case of the samples with 0.5mm stitch spacing. The impact failure force increases with the reducing of stitch spacing as well and the impact failure force increased up to 9.4％ which compared to the unstitched sandwich panels. And the impact energy absorption; however, increases about 62.3 % as the stitch spacing is 25 mm, compared to the unstitched sandwich panels. Besides, the debonding area of bottom skin of composite sandwich panels can be constrained by the stitching yarns.
As far as the compression after impact properties are concerned, compared to the unstitched sandwich panels, compression strength before impact and compression strength after impact for the stitched sandwich panels are increased apparently. The increasing of linear density of stitching yarn is the better way to raise compression after impact properties. The compression strength after impact of samples with linear density of stitch yarn of 340 tex is increased about 33.1％ in average.
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