Overview
The main limitation of the current Liquid Composite Moulding (LCM) manufacturing technologies in the fabrication of high quality, affordable and highly integrated aerospace structures lies in their inability to combine the available information (accurate simulations, measurements, experience and knowledge) dealing with the integrated process (resin flow and cure) in a global control system. Future developments require the refinement and integration of existing control approaches.
The following principal and measurable project objectives were envisaged:
- Development of a robust and tool-mounted integrated dielectric sensor cluster to follow the resin local flow (speed, direction) and cure progress accurately and reproducibly.
- Development of an integrated process monitoring system with knowledge-based adaptable monitoring strategy and smart actuators, capable of reducing scrap components by 50%.
- Development of intelligent and optimal on-line flow control validated on the mould filling of high temperature curing composite materials.
- Integration of process (flow and cure) simulation tools to process monitoring systems and injection control equipment capable of reducing LCM product development costs by 40%.
- Guidance of a composites production process through an optimal path for attainment of prescribed component properties, capable of reducing the overall process cycle by 50%.
The project aimed to develop a revolutionary control system applicable to the production of composite materials through a wide range of LCM methods. The COMPROME system utilised the dielectric signal for sensing resin flow and cure processes and consists of:
- an integrated, durable and tool-mounted dielectric sensor;
- a modular monitoring system with embedded knowledge;
- a process control strategy;
- a global integrated process control (IPC) system;
- the manufacturing aerospace components with cost-effectiveness and improved quality.
The objectives were achieved by integrating sensing principles and fabrication practices for compiling a prototype control system linked with industrial Resin Transfer Moulding injection control equipment. The project was organised into nine technical Work Packages:
- Work Package 1: Development and testing of flow sensors for resin direction and speed measurement.
- Work Package 2: Development and testing of integrated (flow and cure) sensors linked to material models for real-time evaluation of process parameters.
- Work Package 3: Development of flow control system with identification parameters and process optimisation tools.
- Work Package 4: Development of an integrated control system, utilising integrated sensors and smart monitoring strategies.
- Work Package 5: Realisation of process control through the development and positioning of process actuators.
- Work Package 6: Development of a global integrated process control system (IPC) for the global consideration of the component size.
- Work Package 7: Implementating the developing technology step-by-step at lab-scale.
- Work Package 8: Pilot-scale implementations at industrial users' manufacturing sites.
- Work Package 9: Certification and exploitation issues.
Each work package dealt with a single item in the development plan.
Funding
Results
A dielectric monitoring system has been developed for the real-time sensing of composite manufacturing processes of reactive thermoplastic materials. In addition, optimised durable non-intrusive interdigitated dielectric sensors have been designed and manufactured for the sensing of resin arrival, viscosity changes as well as material transformation and crystallisation. The dielectric sensors receive the appropriate AC stimuli from the monitoring system while the feedback is recorded and processed by the system providing real-time material state-based information (viscosity, degree of reaction etc.). The system and the sensors were used successfully to monitor the infusion of glassfibre with CBT oligomers and their reaction to form PBT at the end of the process.
Main Project innovations were:
- integrated, durable and tool-mounted dielectric sensor cluster;
- multi-sensor real-time monitoring system;
- interfacing composites process simulation tools with actuators and the monitoring system;
- intelligent guidance of the manufacturing stage at a predefined path of global process conditions towards given final state.
Technical Implications
Benefits to aerospace industry:
Continuous and robust monitoring of material properties in Liquid Composite Moulding (LCM) processes by means of permanently attached in-mould sensors and linked process simulation tools.
The in-mould sensors led to increased cost effectiveness through:
- reduction of scrap,
- shorter process cycles,
- efficient process development,
- elimination of post-process testing.
The linked process simulation tools guaranteed the improved quality:
- composite materials with 'process signature',
- secured closed mould filling procedures,
- increased production reliability.