Microbuckling elastic modelling approach of a single carbon fibre embedded in an epoxy matrix

Carbon fibre alignment defect inside of an epoxy matrix is examined by the use of microscopy and video recording. The initiation and the growth of a fibre waviness defect was monitored during the cure of the matrix. The observations established that fibre defect appears during the hot stage of the epoxy matrix thermosetting reaction. The objective is to evaluate the possibility of a fibre microbuckling mechanism to explain the observations. A first elastic microbuckling model is proposed. Analytical expressions of the necessary elastic load for the appearance of a fibre buckling instability and its associated wavelength are established. The compressive load applied onto the fibre has been evaluated by using finite elements calculations based on mechanical characteristics of the materials. Comparison between the critical microbuckling load and the applied load onto the carbon fibre during the cure is in coherence with the observations. The associated wavelength is discussed.