Determination of anisotropic geometrical parameters for the electrical characterization of carbon/epoxy composite during oven curing

Cure monitoring is an important tool for ensuring manufacturing reliability and reproducibility of composite parts. Among a variety of techniques, electrical measurements are used. However, electrical values are affected by cure cycles and by the rheological and geometrical parameters during curing. All these parameters must be taken into account to establish electrical models. The present paper proposes to study the changes in the geometrical parameters of an oven-cured composite made of T700/M21 prepregs during curing. For this work, microstructural analyses (in the three orthotropic planes) were carried out using specific curing, i.e. by releasing the vacuum at characteristic points (time and temperature). The following parameters were measured (manual and automatic approaches): ply, inter-plies and global thicknesses; percolation parameters; and volume and surface ratios (fibres, matrix and voids). The parameters obtained will be used in future works to define an electrical model for real-time control of the cure process.