단방향 연속 섬유 복합재 횡단면에서 섬유 배열에 따른 응력 분포 변화
Effects of Fiber Arrangements on Stress Distributions over the Transverse Cross Section of Unidirectionally Continuous Fiber-reinforced Composites
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단방향 연속 섬유 강화 복합소재에 대하여 섬유 배열에 따른 응력 분포 양상을 연구하기 위해 단면 형상을 대표하는 체적 요소를 생성하였다. 대표 체적 요소에 횡방향 하중을 가하였을 때, 섬유와 기지재 강성의 차이로 인해 섬유 둘레에서 응력 집중 현상이 발생하며, 섬유 간 좁은 간격 때문에 집중된 응력이 중첩되며 섬유 주변에서 높은 응력이 구해질 것이라 쉽게 예측할 수 있다. 본 연구에서는 섬유 둘레 응력 증감이 단순히 섬유 간 간격 뿐 아니라 섬유의 상대적 위치가 하중 방향과 이루는 각도에 의해서도 결정됨을 보여준다. 정규 육각 구조를가지는 대표 체적 요소의 중앙에 위치한 섬유를 다양한 방향으로 이동시키며 횡방향 하중을 가하여, 섬유 주변 응력이 증가하거나감소하는 양상을 유한요소해석 기법을 이용해 측정하였다. 섬유 간 거리가 최소이면서 두 섬유의중심을 잇는 선분의 방향이 하중 방향과 일치할 때 응력이 최대로 증가하였으며, 섬유 간 거리가 최소라 하더라도 하중 방향에 수직일 때 최대 응력은 오히려 감소한다는 것을 보여준다.
Abstract
Stress distributions dependent on fiber arrangements are studied using the two-dimensional representative volume element (RVE) model for uni-directionally continuous fiber-reinforced composites subjected to transverse tensile loading. It is easily expected that the stresses around the fibers are concentrated mainly due to the stiffness mismatch between the fiber and matrix materials. In this presentation, it is shown that the stresses are not always increased although the distance between two fibers is shortened. The 2D RVE models, originally having a regular hexagonal fiber array, is utilized to study the effect of the fiber locations on the stress distributions. As the central fiber is relocated, the stress distributions around the fiber are obtained through finite element analysis. It is found that the stresses around the fiber are strongly dependent on the fiber distance as well as the angle between the loading direction and the line connecting two fibers.
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