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Developing a Flexible RTM Tool for Aerospace

Thu, 24 September, 2020


TWI is working in collaboration with Loiretech, Brunel University London, Engineering Technology Solutions and Cranfield University to explore a new and innovative automated composite mould tool technology. TWI will contribute its knowledge to the design of complex composite structures optimised for manufacturing, incorporating state of the art ‘in tool’ monitoring during the cure.


Resin Transfer Moulding (RTM) is a composite manufacturing process. In comparison to alternative processes, it offers great improvements in manufacturing efficiency and, for this reason, is established and increasing in use within the aerospace industry.

The RTM process involves laying dry fibres (reinforcement) into a closed mould tool which defines the part geometry. Resin (matrix) is injected into the tool at pressure, impregnating the reinforcement, and the assembly is then thermally cured under pressure.

The placement of dry fibres presents challenges as fibre alignment is key to a balanced laminate. When fabric fibre is misaligned it results in an unbalanced laminate, which causes internal stress resulting in a distorted laminate that does not meet its designed geometry.                                           

In addition to this, the rate of thermal conductivity through the assembly has a direct relation to matrix polymerisation rates. When local areas are subjected to rapid temperature change this also causes laminate internal stress.

Currently, it is common within the industry that composite mould tools needs to be geometrically adjusted, based on the laminate distortion.

The FLEX project is looking to explore the innovative concept of laminate distortion correction. The FLEX mould tools are designed to monitor laminate stress during cure and to adjust the mould tool geometry. The aim is to achieve increased productivity of correct geometry balanced laminates that meet traceable aerospace quality.


To explore automated distortion correction tooling and offer an innovative solution through:

  • Design of a novel RTM tool with distortion compensation capabilities
  • Reduction in lead time to compensate for mould tool adjustment
  • Efficient thermal management of the tooling operation
  • A methodology for an overall design and evaluation of the production cell

Programme of Work

TWI are currently planning the manufacture of laminate prototypes using the FLEX tool concept. Specimens will be subject to shape analysis, non-destructive testing (NDT), and mechanical testing to establish strength parameters. TWI will compare test results and evaluate between FLEX and existing technology.


Future Developments

TWI is looking towards developing the technology with a potential route to market.


This project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 821488”.

For more information please email: