Compression RTM of reactive thermoplastic composites using microwaves and cure monitoring

Thermoplastic-matrix composites are ideal to improve recyclability of composites not to mention easier assembly and repairability. The EC-funded project Recotrans aims in combining the advantages of the Elium acrylic reactive-thermoplastic resin from Arkema with microwave curing and intelligent process monitoring towards sustainable mass production for the European transport industry. Both the microwave heating and the online process monitoring technologies have been successfully used in thermoset-matrix composites, while the new carbon-fibre proof sensors were introduced successfully in a compression high pressure RTM facility. In the present application a microwave heating device has been developed to preheat the liquid resin either after injection and before mould compression or before resin injection in order to decrease resin's viscosity and improve impregnation as well as to accelerate the reaction. Furthermore, through a durable cure sensor installed in the tool, the Optimold cure monitoring system measures the electrical resistivity and temperature of the resin which are directly correlated to the degree of conversion. The use of a preform from recycled carbon fibres makes the implementation of both technologies more challenging as both technologies are prone to carbon fibres so special techniques were used to circumvent the effect of carbon fibres. The first lab-scale trials showed that both technologies can improve performance ensuring the high potential of the Elium resin for high quality thermoplastic CFRPs.