Co-authors​ :

 James UZZELL (UNITED KINGDOM), Laura Rhian PICKARD (UNITED KINGDOM), Ian HAMERTON , Dmitry S. Ivanov (UNITED KINGDOM) 

Conventional manufacturing processes for thermoset carbon fibre-reinforced polymer (CFRP) composites such as autoclaves, ovens and hot press systems exhibit low energy efficiency. This inefficiency arises from the conductive heating mechanism involved in heat transfer from either tooling or surrounding air. Heating of such tooling requires significantly more energy to heat than the composite itself due to its significant thermal mass. Moreover, the application of heat at the laminate surface either from tooling or via air circulation causes a thermal lag in which heat must pass through bagging consumables and is reliant on the inherently poor through thickness thermal conductivity to travel from the surface at which heat is applied to the laminate centre. To overcome this requires excessively long curing cycles which increase energy usage.
A promising alternative for achieving both time and energy efficiency in composite processing lies in electromagnetic (EM) induction. EM induction offers the potential for direct and localized heating of carbon fibres, minimizing energy wastage. The heating generated within a CFRP laminate through induction is volumetric, reducing losses as heat escapes to the environment or accounting for thermal lag. Inductive heating occurs when internal eddy currents are induced within electrically conductive or magnetically susceptible materials in the presence of an alternating magnetic field. In CFRP composites, induction heating is caused by induced eddy currents heating due to the resistivity of the fibres and contact resistance at inter-ply and intra-ply junctions.
The current limitation to induction heating is the non-uniformity of temperature distribution both in plane and through thickness due to the inherent non-isotropy of the fibres within plies of a laminate. This causes a significant difference between the in-plane and through thickness heating potential governed by the electrical and thermal conductivities of the laminate. Due to this, the fibre layup and material architecture have significant impact on the susceptibility to EM fields, heating intensity and the uniformity of the temperature distribution. To counteract this temperature nonuniformity a novel coil geometry has been designed and is presented in a paper by Uzzell et al. [1] utilising a structure of multiple cells to induce several localised heating regions, reducing the impact of low in-plane thermal conductivity. The results of this paper indicate significant potential improvements in temperature homogeneity in plane as can be seen in Figure 1 allowing further developments for energy efficient applications.
In this study, the induction heating setup demonstrated in the paper has been utilised to cure CFRP plates in contrast to conventional curing using a convection oven. The energy required for these curing cycles has been monitored and compared. The results will be used to demonstrate potential energy savings possible using induction heating.