Induction heating of carbon fiber composites: Investigation of electrical and thermal properties

Carbon fiber reinforced plastics, CFRP, are attractive materials not only because of their strength and stiffness but also because of their electrical conductivity and high thermal conductivity and diffusivity. One application where induction heating of CFRP is particularly interesting is tools for fast thermal cycling, beneficial in many industrial processes, for example in composite manufacturing. The electrical properties make it possible to heat with induction and the high thermal conductivity allows fast heat equalization. In order to control inducting heating of CFRP it is desirable to know the electrical and thermal properties of the composite. This work presents developed experimental methods that are used in an investigation of how the thermal and electrical properties of CFRP structures are affected by the fiber properties and composite structure. The experiments and simulations show that fiber type and fiber volume fraction are of great importance for the electrical and thermal properties. The relation between fiber volume fraction and equivalent resistivity is nonlinear and the experiments indicate that a fiber volume fraction exceeding 60% is necessary to achieve a fairly isotropic resistivity and uniform induction heating pattern.