The processing of composite materials into finished parts has generally taken longer than their metallic counterparts but with these materials now making inroads into high volume sectors such as automotive, and ramp-up rates in established markets such as aerospace increasing all the time, the need to increase throughput is becoming essential.
Automation in the form of systems such as automated tape laying (ATL), automated fibre placement (AFP) and resin infusion have been developed to help speed up and make the lay-up process more consistent, but this is just one half of the equation. Just as significant in speeding up production rates is the development of chemical (resin) products and prepregs that cure faster, are more flexible and easier to handle.
Solvay Composite Materials is at the forefront of developing resin systems, processes and materials intended to help reduce cycle times of composite part manufacture, especially in sectors such as aerospace.
Frank Nickisch, Solvay Composite Material’s global director for strategic projects comments: “Nearly all of our product portfolio has automated product forms for the systems we produce whether that is thermoset structural materials, surface materials, thermoplastic composite materials or textiles. We aim to improve the material’s consistency and quality and eliminate defects so that when our customers use them in a fabrication process there are no interruptions or downtime.”
Solvay has developed resin systems and prepreg resin products with rapid cure times such as SolvaLite 760 and 730 specifically designed for hot compression moulding and high volume applications. It also works to develop resins that can be applied with resin infusion technology (RTM) and Vacuum Bag Only (VBO) prepregs for out of autoclave production. The chemical specialist also provides thermoplastic resins and prepregs which can be stamped or moulded in a press for much faster production of parts, with the added benefit of being recyclable.
Rob Blackburn, Solvay application engineering director says: “By embedding the factors of the manufacturing environment within the development cycle of our products, it allows us to observe how that material responds to an automated situation. Automation has to be considered early on in our development cycle, so that we can accelerate how we develop products that give us confidence in their quality and robustness for the market.”
Materials that can be processed without the need of an autoclave have the potential to ease and accelerate production processes by removing what can be a time-consuming operation as parts are loaded and then heated for curing. However, until recently for critical primary structures found in aircraft this was the only option for manufacturers.
Solvay has supplied AeroComposit with its PRISM EP2400 epoxy resin and dry tape textile to manufacture wing structures for the Russian Irkut MS-21 passenger aircraft. These products – now qualified by the United Aircraft Corporation – can be used without the use of an autoclave.
Nonetheless, Blackburn believes the use of the autoclaves for primary structures in aerospace applications still has a long future, especially for the primes and OEMs who have invested heavily in increasing their capacity for the process.
There could however be opportunities for secondary structures to be manufactured more rapidly out of the autoclave. Thermoplastic products especially have potential in this area.
Nickisch states: “There are some semi-automated thermoplastic processes that are reasonable in terms of the throughput that also provide the quality and consistency for secondary structures. We believe there will be more applications like this where thermoplastic composites have a good business case versus metals or existing thermoset composites.
“But for larger primary structures a lot more technology needs to be developed, especially in terms of automation. ATL and AFP doesn’t really exist for thermoplastics at this point and high performing polymers generally require high processing temperatures.”
With most major passenger aircraft programmes and supply chains well-established I ask if there will be many opportunities to develop new rapid product formulations and processes for Solvay?
“There will be upgrades to existing programmes,” Nickisch continues. “It really comes down to whether the new part, material or process is more cost competitive than the existing one. Most importantly does it achieve the production rates required, which is vital in the single aisle market for example, and are there any other benefits that might be considered.
“As long as the new technology provides a lower cost option then the OEMs will want to adopt it. That may mean replacing an existing composite technology with a lower cost composite alternative, or replacing metal if there is a business case.”
Blackburn affirms that an emphasis on collaboration amongst all industry stakeholders is the best way that reduced cycle times can be met by automation.
“Industrialisation is a challenge for our customers, ourselves, our suppliers and the manufacturing equipment manufacturers,” he explains. “It is only by working together that we can achieve what our customers need. We have to become more creative about how we come up with automated systems. We have to go beyond the boundaries that have been established in the industry today. It may be a case of looking at how different robotic systems interact with one another to create a hybrid solution.”
As the composites industry matures it is moving away from the low volume, high-end and R&D production numbers that were once required. This means a whole new approach is needed for composites to reach their full potential.
“If we look at the early uses of composites in the aerospace industry everything was driven by the performance specification of the material,” Blackburn states. “Our aim was to see how we could meet the key properties with the chemical formulations that we could develop and with the fibres that we used.
“That still has to be maintained, but now there is also strong focus on the processing specification so we have a solution that not only meets the performance requirements but is also robust enough for modern manufacturing and automation.”
And Nickisch emphasises as composite manufacturing becomes more demanding, then Solvay has to provide reliable solutions to compete.
“We have to keep a strong focus on our customers’ needs and on the needs of the market so that we develop the right technology for the right application. When we commercialise a new product, advances in manufacturing technology also have to be part of that commercialisation.
He concludes: “We have to deliver reproducibility. It may mean a sizeable upfront investment for us but we have to do it to eliminate any problems that may be in the product before it is fully introduced into the market. Industry does not have time for failures. Once our products are in the market they have to deliver reliability.”