탄소섬유와 epoxy 수지의 prepreg로 성형된 Cross형 적층판 복합재료에서 unfit ply의 두께가 복합재료의 기계적 성질에 미치는 영향과, unidirectional prepreg 및 fabric prepreg로된 적층판의 기계적 성질의 차이를 비교 검토하였다. 그 결과 unit ply의 두께가 두꺼울수록 면내전단강도는 작아졌으며, 면내전단강도가 작아 질수록 층간박리 현상이 현저하게 나타났다. 또 적당한 층간박리의 발생은 파괴인성치와 층격치를 증가시키지만 심한 층간박리는 오히려 그 값들을 감소시켰다. 그리고 unidirectional prepreg로 성형된 적층판이 fabric prepreg로 성형된 적층판보다 인장강도, 파괴인성치, 파괴일 및 충격치 등의 기계적 성질이 우수했다.

The study was conducted to evaluate reliability of the longitudinal tensile properties of unidirectional carbon fiber reinforced composites. Two kinds of carbon fiber reinforced composites laminates were tested in order to examine the factors of variability and have the information concerning reliability improvement. Temperature dependence of the strength and its variability were investigated by means of testing at two kinds of temperatures. Statistical distributions of the respective mechanical properties were obtained from the tensile tests. As a result, strength of composites was directly proportional to the ultimate strain and was not proportional to the elastic modulus. The fracture behavior in bending of notched plate was studied for a composite material. The uniform bending tests of notched plates have been carried out for a wide range of notch radii. The experiment shows that the nominal stress at failure decreased with decreasing notch radius and it approaches a constant value when the notch radius is less than about 0.3mm. The critical maximum stress is governed by notch root radius alone in the case of a constant thickness of specimen.