Cure Monitoring of Composites Using Heat Flux Sensors

Principle

Heat flux sensors facilitate contact less monitoring of transfer of heat in metallic tools. As heat is generated by almost all thermosetting materials at the time of their reaction, the sensor is sensitive to the cure reaction. This information can be used for end of cure detection with proper treatment in real time.

Positioning of Sensor

The heat flux sensorssensor determines the internal mold heat flux, which is closely linked to exchange of heat between the tool and the material. The sensitivity of the sensor is good enough to make measurements without any direct contact with the material to be cured. The sensor should be placed in the mould at a 1 mm distance from the surface. The precision of tooling for the housing is weak as there is no direct contact with the material. The sensors do not undergo wear and can be retrieved when the mould is cold.

The signals given out by the sensor are analyzed in real time by an electronic device. The device can also detect end of cure and send an electrical signal to the press so that the cure cycle is stopped automatically. The system thus adapts to the reactivity variability of the processed part.

Typical Results

Manual processes have more variability compared to automated ones. They present variability of ±20% in reactive cure times, leading to a 10% increase in global productivity.

Possible Extensions

A computer connection to the system permits signals data-logging and settings procedure. It makes trials traceable and enables analysis of production drifts. Statistical process control (SPC) software module enhances data handling efficiency and can be utilized as an automatic precise data feeder for day-to-day monitoring of production.

Benefits

State-of-the-art engineering aids such as the use of heat flux sensors achieve the following:

• Better piloting and control tools design, generally without direct contact
• Optimization of production cycles as well as ensuring quality
• Decrease variable costs to enhance profitability

Applications

Heat flux sensors find applications in SMC, BMC, RTM, RIM, injection, liquid casting, and rotomoulding in the automotive, electrical, and building sectors.

About TFX-SA

TFX-SA design and implement in-line material control solutions.

Tfx-Technology® products, also known as Thermoflux are :

• Thermal sensors (Heat Flux sensors or Heat Flow sensors) : there is no mastership over the quality of your products without thermal control. Heat spreads and vehicle information! It is therefore possible to control a product without direct contact.
• Monitoring and control systems
• Industrial acquisition and post processing software
• Traceability of technical operations performed everyday

This information has been sourced, reviewed and adapted from materials provided by TFX-SA.

For more information on this source, please visit TFX-SA.