Reducing energy consumption when consolidating composites

Sirris has developed a technique for drying oven forming of thermoplastic composite materials that saves nearly 60% in energy consumption.

In order to reduce the carbon footprint of thermoplastic composites, and in the framework of its Product Development HUB Hybrids Lab, Sirris has developed and validated a vacuum bag consolidation method that is particularly economic for this type of material. Indeed, energy savings of up to 60% have been demonstrated.

The concept involves the dissociation of thermal cycle phases, an operation made possible via the acquisition of a thermo-efficient drying oven based on an innovative concept. Sirris had a bypass installed at the base of the machine door, hence enabling different cables and pipes to be passed for controlling the vacuum and temperature, using thermocouples. These elements are connected outside of the drying oven.

The following pictures illustrate the concept:

Whereas a standard vacuum consolidation cycle implies the entire system to be connected in a cool state, inside the oven, the device developed by Sirris enables the drying oven to be preheated, consequently maintaining its temperature levels over several forming cycles.

This offers an unquestionable advantage, given that the heating phase is the most energy-consuming for it involves, not only the product requiring consolidation, but the oven itself.

The drying oven can be unloaded hot, and parts cooled outside, hence further reducing the total cycle time and providing an oven interior already fit for a new cycle, a new part, etc.

The following photographs illustrate the handling operations for consolidating a thermoplastic composite cycle saddle.

The technique’s efficiency has been proven:

  • Producing a cycle saddle via a standard sequence - heating, stabilisation at the desired temperature (i.e. 220°C for 1 hour 30 minutes in our case), then controlled cooling (of 3 hours 30 minutes) - consumed 34.2 kWh and the entire cycle took 6 hours.
  • The sequence production of 4 saddles with one single heating operation, a lengthy but low energy-consuming temperature level, no active cooling, since this is done outside the drying oven, took 7 hours and consumed 56.8 kWh, i.e. 14.2 kWh/produced part.

The ratio of these 2 values is 14.2/34.2 = 0.41 in other words an energy gain per part of 59%!

This demonstration was conducted within the framework of the MACOBIO ERDF project.