フェノール樹脂積層板の回転曲げ疲労試験

Abstract

A rotating bending fatigue test was conducted for the phenolic resin laminates. The purpose of this test was to investigate the effect of the difference of base cloth and of cut out direction of test piece (parallel to the warp or woof of the cloth) on the fatigue strength.In the fatigue test of high polymer material, it is generally known that specimens produce a considerable heat. The problem of this heat producing has not been analyzed, because of the difficulties in measuring the temperature of rotating beam specimen. Therefore, we coated thermopaint on the surface of the specimens in all the fatigue tests so that the temperature might be measured, and obtained, for the high polymer materials, S-N curves different from those for metallic materials.Main test results obtained are as follows: Rotating bending fatigue limits of phenolic resin laminates show no great difference among laminates of various cotton cloth. The fatigue limit of fiberglass cloth laminate is about twice as high as the former. Between the specimens cut out from the laminate parallel to the warp and woof of the cloths, it is difficult to determine which is more endurable.The S-N curve of cotton cloth laminates consists of two curves for the smaller and larger total numbers of revolution. This is due to the internal heat producing phenomenon of specimen. The effect of internal heating on the fatigue strength is remarkable for the smaller total number of revolution (N<105-106), and is not for the larger one (N>105-106). Accordingly, at a fatigue endurance limit (N=107), its effect seems to be negligible.