To study the stress concentration phenomenon at a crack tip by changing the filler site in polymer composite materials, model specimens for photoelastic test were prepared with notched epoxy resin plate in which a small copper plate or a metal fiber was embedded as a filler. The stress concentration factor was measured under tension and bending by changing the distance between the notch and filler, the filler length, and the notch position of filler from the center to the end. Under tension, the stress concentration factor reduced as the distance between the notch and filler decreased, or as the length of filler increased. When the notch was located at the end of filler, the stress concentration factor reached to maximum. On the other hand, the stress concentration factor reduced as the distance between the notch and filler decreased undor bending. If the filler was located between the notch and the neutral point, the stress concentration factor decreased as the length of filler increased. However, when the filler wasn''t located between the notch and the neutral point, the stress concentration factor increased reversely as the length of filler increased. Finally when the notch was located at the end of filler, the stress concentration factor increased only slightly and maintained constant as a whole.

복합계내 충전보강제의 위치에 따라 crack 선단부에서의 응력집중현상을 고찰하기 위해, notch를 갖는 광탄성용 Epoxy판에 판장과 섬유장 충전재를 함침경화시켜 모형식편을 제작하고 이때 notch 선단과 함침 충전재와의 거리, 충진재의 길이를 변화시키고, 충전재 중심에서 말단으로 notch의 위치를 이동시키며 응력집중계수를 인장하중과 굽힘하중 하에서 측정하였다. 인장하중을 가했을 경우, notch 선단과 충전재사이의 거리가 가까울수록, 충전재 길이가 길어질수록 응력집중계수는 감소하였으며, notch가 충전재 말단부분에 위치할 때 급격히 증가하였다. 한편 굽힘 하중을 가했을 경우에는 notch 선단과 충전재 사이의 거리가 가까워 질수록 응력집중계수는 거의 직선적으로 감소하였으며, 충전재가 중립점을 중심으로 notch에 가까이 있으면 그 길이가 길어질수록 응력집중계수는 감소하지만, 멀리 있으면 오히려 증가한다. 반면 notch가 충전재 말단부에 존재할 때 응력집중계수는 약간 증가할 뿐 전체적으로 일정한 값을 갖는다.

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