Papers by Author: Hermawan Judawisastra

Abstract: Glass fiber reinforced polymer (GFRP) is a common composite material used for wind turbine blades because of its good strength to weight ratio. This paper describes the design process of GFRP material for a low wind speed (LWS) turbine blade. The wind turbine analyzed in this study is a 3-blades horizontal axis wind turbine (HAWT) with NACA 4415 airfoil and rotor diameter of 5 m. Parameters for the blade are thickness of skin and spar, lamination angle, and stacking sequence of the laminae. The design approach uses Carpet Plot Method based on Tsai-Hill failure criteria. Materials analyzed in this study are unidirectional E-glass fiber/epoxy composite and plain weave woven roving WR200 E-glass fiber/epoxy composite. There are 15 material configurations analyzed using a finite element software. The result shows top five of the composites configuration consisting of minimum 3 plies of 0°/90 direction fiber for the skin and ±45° direction fiber for the spar. The optimum configuration is [(0/90)]3 for the skin and (±45) for the spar both using plain weave woven roving WR200 E-glass fiber/epoxy composite. This configuration has margin of safety of 1.42 based on maximum principal stress and maximum deflection of 346 mm which is 0.14 of the total blade length. The predicted overall weight of the blade is 1.52 kg.

Abstract: In this research, the influence of processing temperatures and fiber chemical treatments to mechanical properties of polypropylene (PP) waste – kenaf fiber composites was investigated. Results from experimental and theoretical calculation of composite tensile strength were compared. The composites were made of PP wastes and unidirectional kenaf fiber, and manufactured by hot press molding. The processing temperature variations were 175 oC, 185oC and 195 oC. The chemical treatment used were alkaline and permanganate treatment. Kenaf fiber – PP composites were successfully made with the void volume fraction less than 5%, maximum fiber volume fraction 48% and maximum longitudinal tensile strength 110 MPa or 238% higher than PP’s strength. For non- and alkali treated fiber composites, 185oC was the optimum processing temperature. Elevated processing temperature up to 195oC could decrease composite strength due to the degradation of fiber-matrix interface. The effect of permanganate treatment did not significantly affect the composites strength. However, the improvement of interfacial properties at elevated temperature was found by the use of permanganate treatment.