Study of Elastic Behaviour of Bolted Sandwich Beam With Unidirectional Carbon Fiber Skins

Sandwich materials with reinforced composite skins become currently a relevant choice to obtain both strength and lightweight structures because of their optimal mechanical performances provided by having just a moderate volume ratio of rigid fibers. Therefore, composite sandwiches are strongly recommended for wind turbines blades that need lightweight materials to achieve optimal power efficiency with an increased size. In this paper, a bolted sandwich beam used for wind turbines with skins reinforced by unidirectional carbon fibers is studied through realizing a numerical simulation under commercial software in order to evaluate an analytical model proposed to predict tensile elastic modulus. For that, several simulations of tensile tests were performed for many samples of sandwich beams and their composite skins with a fiber volume fraction of 15% and two reinforcement orientations that are 0° and 45°. The study results approved the analytical approach especially for sandwich specimens where elastic core absorbs shear energy and composite skins influence sandwich rigidity that equals to 4.6 Gpa for the case of a reinforcement orientation of 45° and 11.8 Gpa for 0° fibers inclination. Then, the application of various bolt preloads causes a tensile modulus drop because of concentrations of constraints which requires a suitable selection of fibers angle, tensile load and bolt material to conserve beam rigidity.