Small and large manufacturers of aerospace parts, recognize the problem. Light weight and strong composites can be shaped in complex forms and in many cases they are far superior to their metal counterparts. In theory this renders them into ideal materials compared to the alternatives.
Unfortunately, to get the best performance they require treatment in a high pressure and high temperature oven. In the aerospace sector this manufacturing step is absolutely necessary because they turn the flexible fiber mats used into rock-hard components stronger than steel and lighter than aluminium.
This oven or autoclave allows the resin infused into the carbon-fiber matrix to cure or harden at optimal pressures and temperatures of around 180 °C in an incremental process that can take more than a day. Their operational use also come with hefty electricity bills and many lost hours in the pre- and post-processing of sometimes a single part. Especially for the production of larger parts, like entire wings or airplane and rocket hull structures, this pressure resistant oven becomes a very heavy, critical and expensive piece of equipment, with a large footprint on the factory floor when not in use. Because of their high cost, autoclave manufacturing processes are time-consuming bottlenecks holding up the entire production line.
Because of this, and despite their inherent benefits, composites are still only used in sectors where the high performance of the parts outweighs the costs involved or where use of the weaker non-autoclave version is ‘good enough’. This however is about to change in a drastic fashion.
Thanks to a recent advance in chemistry, a revolution in material sciences engineering is now at hand.
A curing strategy, called frontal polymerization, demonstrated by researchers of the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign, and reported in the Nature issue of 8 may 2018, is able to slash cost and the required time of manufacturing these aerospace grade parts hundreds and even thousands of times. No longer will an autoclave be needed to always get optimal material performance. If the benefits are realized in the field, this would mean small manufacturers and industry start ups can offer expert quality and build large aerospace structures without needing the large upfront capital investment usually required.
As the lead author the report, aerospace engineering professor and lead author Scott White, confided to Phys.org: “This development marks what could be the first major advancement to the high-performance polymer and composite manufacturing industry in almost half a century.”
Nor will the dreamy visions of engineers and manufacturers be limited to the size and affordability of any commercial autoclave in existence. Energy efficient but difficult to manufacture shapes, such as the futuristic blended wing body airplanes (take for example the X48B configuration), with airplane hulls larger than an Airbus 380/Boeing 747, now become possible at far lower price-points (e.g. price of an A320/Boeing 737).
Or as the abstract of the Nature article, reads:
“Frontal polymerization is a promising alternative curing strategy, in which a self-propagating exothermic reaction wave transforms liquid monomers to fully cured polymers. We report here the frontal polymerization of a high-performance thermoset polymer that allows the rapid fabrication of parts with microscale features, three-dimensional printed structures and carbon-fibre-reinforced polymer composites. Precise control of the polymerization kinetics at both ambient and elevated temperatures allows stable monomer solutions to transform into fully cured polymers within seconds, reducing energy requirements and cure times by several orders of magnitude compared with conventional oven or autoclave curing approaches.”
“Precise control of the polymerization kinetics at both ambient and elevated temperatures allows stable monomer solutions to transform into fully cured polymers within seconds, reducing energy requirements and cure times by several orders of magnitude compared with conventional oven or autoclave curing approaches.”
“The resulting polymer and composite parts possess similar mechanical properties to those cured conventionally. This curing strategy greatly improves the efficiency of manufacturing of high-performance polymers and composites, and is widely applicable to many industries.”
This would imply that professionals, but also home fabricators and composite enthusiasts working in a tidy garage, now have the ability to produce parts with professional grade strength and quality, without needing the usual traditional and expensive setup. Hobbyist home construction of e.g. Kit airplanes and less demanding automotive parts would be cheaper, but also and importantly, safer in operational use while being easier, faster and requiring less tooling than metal construction techniques.
This is an exciting development that we are eager to follow up at ONESTAGETOSPACE.COM in future articles and programmatic steps. We congratulate the researchers with their achievement.
For more details and contact details of the researchers, see:
- Original Nature article: Rapid energy-efficient manufacturing of polymers and composites via frontal polymerization: https://www.nature.com/articles/s41586-018-0054-x (Naturevolume 557, pages223–227 (2018), doi:10.1038/s41586-018-0054-x)
Abstract:
Thermoset polymers and composite materials are integral to today’s aerospace, automotive, marine and energy industries and will be vital to the next generation of lightweight, energy-efficient structures in these enterprises, owing to their excellent specific stiffness and strength, thermal stability and chemical resistance. The manufacture of high-performance thermoset components requires the monomer to be cured at high temperatures (around 180 °C) for several hours, under a combined external pressure and internal vacuum. Curing is generally accomplished using large autoclaves or ovens that scale in size with the component. Hence this traditional curing approach is slow, requires a large amount of energy and involves substantial capital investment. Frontal polymerization is a promising alternative curing strategy, in which a self-propagating exothermic reaction wave transforms liquid monomers to fully cured polymers. We report here the frontal polymerization of a high-performance thermoset polymer that allows the rapid fabrication of parts with microscale features, three-dimensional printed structures and carbon-fibre-reinforced polymer composites. Precise control of the polymerization kinetics at both ambient and elevated temperatures allows stable monomer solutions to transform into fully cured polymers within seconds, reducing energy requirements and cure times by several orders of magnitude compared with conventional oven or autoclave curing approaches. The resulting polymer and composite parts possess similar mechanical properties to those cured conventionally. This curing strategy greatly improves the efficiency of manufacturing of high-performance polymers and composites, and is widely applicable to many industries.
News report:
- phys.org: New polymer manufacturing process saves 10 orders of magnitude of energy https://phys.org/news/2018-05-polymer-magnitude-energy.html
