Abstract
Glass fiber reinforced plastic bolt (FRP bolt) has been applied to several equipments or structures, as it has good chemical, mechanical and electrical properties such as a corrosion resistance or a large strength/density ratio. Recently, according to the development of super conducting technology, its fatigue property at low temperatures also has become important.
In this report, the FRP bolt which had a center roving and a braid structure was chosen and its fatigue behavior at R.T. and 77K was investigated. As the results, the following conclusions were obtained:
(1) Although the fatigue strength was hardly dependent on a reinforcement fiber structure in FRP bolt, it was increased at 77K compared with at R.T..
(2) The fatigue fracture of FRP bolt was caused by the initiation and the propagation of 3 types of cracks. The first was on a reinforcement fiber bundle/resin matrix interface, the second was in a reinforcement fiber bundle and the third was in resin matrix.
(3) As these cracks were considered to be initiated depending on stress state, it was clarified that the first type crack above mentioned was formed easily at a high shear stress field.
