The benefits of Liquid Resin Infusion and RTM are diverse. Reduced CAPEX and OPEX, along with significant efficiency and energy savings can be achieved while also significantly improving manufacturing rate.
As part of this requirement, Composite Integration has collaborated with aerospace clients for more than 20 years, evaluating and developing the key principles necessary to produce very high-quality composite parts in an Out of Autoclave method.
Figure 1 represents an example of the type of process envelope which must be followed to ensure the quality and repeatability required by this sector.
One of the key fundamentals necessary for both measurement and control on liquid processes is pressure. Vacuum level measurement is a given, but careful control of liquid resin pressure is less well understood and has a significant impact on final laminate quality, volume fraction (Vf) and void content.
Pressure measurement is key in various stages of the manufacturing timeline, including pre- infusion, during infusion and post infusion. Information provided from pressure sensors is used at each of these stages to ensure correct management and control of the process.
Innovations over the past few years have led to the development of a reusable ceramic In Mould Pressure Sensor (IMPSTM) capable
of directly measuring resin pressures across diverse temperature and pressure conditions and permits meticulously controlled resin delivery and cure. This allows for exceptional accuracy and consistency in composite part production, which is crucial for both quality and performance.
Figure 2 – IMPS sensor testing and laminate quality experimentation.
In 2024 Composite Integration introduced a redesigned sensor face and a novel ceramic surface coating to improve durability and accuracy over time. These enhancements, aimed at significantly extending the lifespan in a very challenging manufacturing environment, continue to be under rigorous evaluation by their research and development team.
Effective measurement of this parameter is fundamental to the quality of laminate fabrication. It permits careful control of laminate Vf and can support reductions in void content—both common issues that undermine a composite’s performance.
In addition, measurement of resin pressure permits resin delivery equipment to be precisely automated, leading to a simplified, repeatable, and carefully controlled infusion.
Figure 3 - Laminate quality as a function of process pressure control.
Figure 3 above demonstrates the significant impact that precise control over infusion pressure and de-gassing efforts can have on laminate quality.
By adjusting these variables, amongst others, manufacturers can visually assess and optimise the final product, ensuring consistent high-quality outcomes across various production scenarios.
This level of precision is absolutely crucial, from producing small-scale components, right through to large structures such as wing spars.
Verification of these results is carried out using microscopy, to include void content analysis and mechanical ILSS testing.
Figure 4 – Typical microscope images of successfully processed composites in glass and carbon fibre.
Incorporating these sensors into advanced machinery, such as Composite Integration’s CIJECT machines, demonstrates the seamless integration of technology and operational efficiency. These machines autonomously adjust resin feed pressures based on real-time data from the IMPSTM sensors, simplifying tasks for operators and ensuring consistent quality.
CIJECT control software algorithms have been developed over a 20 year period to be industry leading in terms of accuracy of pressure control, ratio control (where applicable) and ability to respond quickly to a wide range of sensor inputs, including up to 24 pressure points simultaneously. The data from these sensors is also logged in CIJECT equipment, along with a multitude of process parameters, providing a deep package of data, essential for quality control and process optimisation.
Looking ahead, the connectivity options for these sensors are set to expand. Composite Integration is introducing an updated multi-way readout unit and a new, compact handheld unit in 2025, enhancing accessibility and versatility. An independent data logging unit, the CIDAQ is already available. These innovations reflect a broader trend towards smarter, more connected manufacturing environments.
The continuous development of in-mould pressure sensing technology underscores the industry’s drive towards more precise and reliable manufacturing processes.
With ongoing enhancements, Composite Integration is helping ensure that the aerospace manufacturing sector meets the highest standards of quality and efficiency. This is paving the way for higher quality, more cost effective parts at higher production rates.