Effect of gelcoat thickness on laminate composite structure and strength

Goh, Chun Hsien (2015) Effect of gelcoat thickness on laminate composite structure and strength. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

The aim of this study was to evaluate the effect of different gelcoat thickness on laminate composite structure and strength. The gelcoat is prepared by hand lay-up method and continue by fabricate the glass fibers reinforced composites on top of the gelcoat with vacuum bagging process. The mechanical properties and interfacial bonding of the various gelcoat thickness on laminate composite were tested by using three-point flexural test and tensile test. A further comparison was made with the corresponding mechanical strength of different gelcoat thickness laminate composite. The fracture behaviour of different gelcoat thickness is monitor under the scanning electron microscope to determine the type failure occur after the mechanical test. From two-way flexural test in mean by placing the samples where gelcoat layer on facing top and bottom position had shown that 0.30 mm was the highest mechanical strength. The gelcoat layer facing top which was facing the compression load had shown decrease 54.39 % and was similar to gelcoat layer facing bottom had decrease 45.07 % when reach 0.40 mm. It was due to higher the gelcoat thickness had increased the brittleness of the laminate composite that sudden fracture occur in facing load. Tensile test was intensive to investigate the interfacial bonding in between gelcoat and laminate composite had indicated 0.40 mm is the highest in sustain the pulling force and compare interfacial bonding strength to clean laminate composite without gelcoat, it had increased 37.94 %. The failure behaviour occur were caused by the delamination of matrix between the plies where the gelcoat still strongly bonded with laminate composite. Despite there are no significant gelcoat thickness specified in previous study, it was not highest the gelcoat thickness better the mechanical strength while suitable thickness is required as design for outermost protection.

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