Design and Development of Plane Bending Fatigue Testing Machine for Composite Material

Abstract

Fiber reinforced composite materials are finding increasing applications in aerospace structures, naval industry, military and automotive industry, because of their high specific stiffness and strength. Although the fatigue behavior of fiber reinforced composites has been studied for a long time, the fatigue of composite materials is not completely understood as the fatigue in composites is quite different from metal fatigue. From the literature review it is revealed that less number of fatigue life prediction models are available for composite materials and majority of the research work is related to the tension-tension fatigue and tension-compression fatigue but less work is reported in bending fatigue life estimation.In this paper the development of a plane bending fatigue testing machine for composite material is presented. The work is undertaken considering the high cost of the presently available fatigue testing machines. Copan shaped work pieces are used for the testing. Specimens are subjected to repeated fluctuating stresses and the number of cycles is counted till the breakage of the specimen and the results are plotted. The proposed machine is simple in design and economical. An eccentric cam and connecting rod arrangement is done for the fully reserve bending motion of the work piece. The machine is equipped with speed measurement, speed control, force measurement, displacement measurement and fatigue life measurement and data acquisition system.For the validation of the machine, the fatigue testing of some samples is carried out and the results are presented to show the efficiency of the system. The results show that the machine is capable of satisfying the requirements of ASTM standard.