Measurement and analysis of residual stresses in single fiber composite

This paper deals with the thermal residual stress of carbon fiber-reinforced composite, which arises from the different coefficient of thermal expansion (CTE) of constituents during cooling from the processing temperature down to room temperature. It is studied by experiment and theoretical analysis. In experiment, the real-time electrical resistance detection method is applied to measure the carbon fiber electrical resistance, where the single carbon fiber itself is used as internal sensor in composite material. The axial residual strain and also stress is obtained by the relationship between strain and electric resistance based on its electrical property. To explain the experiment data, a 3D theoretical column model with three phases was established to calculate the unit cell stress field by governing equations and boundary conditions. Result shows the experiment data is approximately close to theoretical model; meanwhile, theoretical model gives more detailed stress distribution, which is difficult to measure, in three directions of all phases.