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COMBUSS: Novel, multi-zone, self-heated out-of-autoclave composite tool

Autoclave manufacturing is regarded as a benchmark in the production of quality, aerospace composite parts.  However, high accrual and operational costs limit their practicality for smaller-scale companies and are a barrier to production rates.  In the COMBUSS project, a multi-zone, self-heating composite tool was developed to manufacture complex, high-quality, out-of-autoclave, lower wing stiffened, composite panels.

The demand for thermoset composite parts is growing in terms of number, size and complexity as more industries use them in their production lines due to improved properties, therefore, finding better manufacturing techniques is vital.  One of the benchmark manufacturing methods used is autoclave curing which, when applied in the production of thermoset composite parts, ensures high-quality composite components.  Nevertheless, the costs of acquisition, operation and tooling are high.  Additionally, large autoclaves must sometimes be used inefficiently for small parts, which consumes excess energy.  This means that using autoclaves is not sustainable, thus limiting expansion in composites growth.

The aerospace industry is keen to develop and use out-of-autoclave processes, therefore, COMBUSS aimed to speed up manufacturing times and reduce costs without sacrificing quality.  The project succeeded in building a tooling system that incorporated self-heating capability with multiple heating zone, and advanced thermal management, to manufacture business jet, lower wing stiffened panel.  Key objectives of COMBUSS were to design a tool configuration compatible with the desired part, identify an efficient and safe heating method and integration strategy, and balance product quality and energy consumption by developing a thermal management system that controls heated zones individually.

This resulted in the manufacture of business jet, lower wing stiffened panels using carbon fibre reinforced Polymer (CFRP), which minimises the effect of differing thermal properties, and; provides a durable tool that can support and withstand many heating cycles.  The tool was designed and manufactured by project partner OMI S.R.L.

In order to make the tool usable in production lines, the heating elements needs to be well-distributed, fully integrated with the tool material, and safe to operate and maintain.  To satisfy these requirements, heating fabric is used to generate the required heat in multi-zones of the part, and distribute it evenly with proximity to tool and part surfaces.  In addition, its thin and light laminate shape enables a high level of mechanical bonding with the tool.  A thermal management system was created to efficiently control the thermal cure of the resin.  Each heated zone employs a graphical user interface (GUI), temperature data acquisition system and proportional integral derivative (PID) controllers that are also able to receive feedback.

On completion, COMBUSS delivered a multi-zone, self-heating, composite tool for manufacturing high quality, stiffened, lower wing panels parts while reducing costs and energy consumption, compared with autoclave processes.  The heating elements are embedded within a robust tool while being controlled by a thermal management system.

Partners: OMI SRL, as Project Coordinator, and BCC.

COMBUSS received funding from the Clean Sky 2 Joint Undertaking under the European Union's Horizon 2020 research and innovation programme under grant agreement No. 821297.

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