Background

For maximum mechanical performance, composite materials must be cured at high temperatures. For manufacturers, this process is energy-intensive and uses expensive equipment such as an autoclave or oven. Rapid heating reduces time and energy use but risks triggering a runaway exothermic reaction. Such inherent overheating results in scrapped parts, damage to equipment or even fire. For a large, high lag system, applying too much power at the wrong time in the cycle may make an exotherm unavoidable, but that may not actually become apparent for up to 30 minutes at which point it is too late to avoid. As a result, composite curing processes are highly conservative, using very slow heating rates and long isothermal dwells.

The University of Sheffield’s Advanced Manufacturing Research Centre (AMRC) researchers have developed a code (CureAll) which controls the curing process based on a prediction of its future state, allowing the temperature profile to run as close as possible to the exothermic limit without ever exceeding it.

Technology Overview

The CureAll code is a package of Python objects and functions which analyse both the composite material and its surrounding system, fitting a large set of parameters. This parameterisation allows the code to make predictions of the future effects of control inputs. The code has been validated for real-time control of cures on the oven and heated tooling equipment.

The solution can be used offline, to simulate pre-cure or to review data post-cure, or it can be used online, to provide real-time control.

Benefits

CureAll saves time and energy by allowing rapid heating without the risk of triggering a runaway exotherm. An aerospace-grade carbon fibre pre-preg panel which (would normally take 5 hours 30 minutes to cure) was cured in 1 hour 15 minutes, saving 78% of the cure time and 46% of the energy.
Part quality maintained or even improved. In the above work, the void content was lower and the interlaminar shear strength and glass transition temperature of the panel were higher for the more rapidly cured part than the part cured in a conventional way.
The parameterisation of material and system are automatable and variations in the parameters could provide a further metric for quality control.
Hardware is agnostic. Inputs can be thermocouples, Resistance Temperature Detectors (RTD) or dielectric sensors. Outputs can be used to control ovens, autoclaves, heated presses, heated tooling or microwave, resistive or inductive heating.

In order to safely run close to exothermic limits on high lag equipment, a predictive system such as CureAll is essential.

Applications

The code is currently tailored to the needs of curing high-temperature epoxy resin-based materials. These are typically used in the aerospace sector although are increasingly being applied in automotive and renewable energy. The code can also be developed for other chemistries.

Opportunity

Software development and distribution partner.

CureAll: Predictive Composite Cure Optimisation

IP Status

Seeking