HexPly® XF Surfacing Technology Enabling High-Quality Paint-Ready Surfaces for Prepreg and Infused Components

Q: Could you start by giving us a brief introduction to the HexPly^® surfacing technology? What type of product is it and how does it benefit the composite manufacturing process?

AF: “In composite material terms, HexPly^® XF is a lightweight, non-woven, semi-preg, epoxy resin material that replaces traditional in-mold gelcoats used in the manufacture of composite components such as wind turbine blades. For the end-customer, it is an innovative surface technology that removes the need for gelcoat and the time-consuming refinishing work typically required to obtain a paint-ready surface. In short, we are pleased to report that HexPly XF reduces costs and produces lighter, more consistent parts with shorter cycle times and a cleaner working environment.”

Q: Several challenges exist in the composites world at the moment, from raw material supply chains through to end-customer demand. How have these challenges impacted Hexcel’s product development strategy and which markets are you targeting with HexPly XF?

AF: “That is absolutely right. There have certainly been some challenges regarding raw material supply chains in the glass fiber and chemicals markets during the past months, although we have worked extremely hard to minimize the impact on deliveries to our customers. Coupled with this tightening of availability in the supply chain, demand in the industrial composites sector has remained strong. Hexcel has developed HexPly XF to improve production efficiency, ultimately saving time and reducing costs for manufacturers, which is going to be a key driver for the most successful wind energy OEMs in the future. 

Wind energy is certainly a key market but HexPly XF technology is definitely not limited to wind. We have great feedback on the production benefits of HexPly XF from part manufacturers in both marine and industrial markets, too.”

Q: With Wind Energy production processing being a key driver for the HexPly XF technology, can you give us more detail as to how this new material fits into the blade building process? Is it suitable for prepreg and/or infusion blades?

AF: “We have developed 2 variants of the HexPly XF material, one is compatible with prepreg and the other with the infusion manufacturing processes (typically we are talking about customers curing with mold temperatures > 60˚C for infusion). The prepreg version came first and has been well proven by key wind OEM prepreg users, while the infusion version is the product that we are just launching now.

For both the prepreg and infusion versions, HexPly is the first material applied into the release-agent-coated mold. Easy to handle and supplied in a ready-to-use roll form, HexPly XF can be quickly applied by hand or with semi-automated layup equipment.

One side of the product, clearly indicated by a removable protective film, is the self-adhesive surface finishing side which goes down against the mold surface. Once the HexPly XF material has been positioned, the layup of the blade shell structure (fabric or prepreg layers) can start immediately, and the laminate can be infused. After curing, the blade is easily de-molded with the manufacturer benefitting from a paint-ready surface.”

HexPly XF can be quickly applied by hand or with semi-automated layup equipment.

Q: Outside of the Wind Energy market, could HexPly XF be applied in other composite applications? What sort of component types have been identified and can you give us some examples of HexPly XF success stories?

AF: “HexPly XF can be used just as effectively in other prepreg or infused composite structures. Some of Hexcel’s marine customers have been using HexPly XF to improve the surface quality and reduce time and material costs when fairing and finishing parts for the final paint finish. A nice example of this type of application was seen at a leading UK superyacht builder who was able to significantly reduce the paint preparation time for a large hardtop sun canopy by demolding the part with a pinhole-free HexPly XF outer surface. HexPly XF technology also has the potential to remove the need for a cosmetic barrier coat (typically non-structural layers of chopped strand mat used to avoid print-through in production boat builds), hence saving weight, too.

With XF Technology paint ready surface finish

In addition, XF technology is also well adopted in the automotive sector for the manufacture of high-quality Class A body panels – an application with the highest surface quality standards in the composites industry. Each year, thousands of high-performance cars are built using HexPly XF products, demonstrating the exceptional surface quality performance of HexPly XF. 

XF Technology for aesthetic body panels 

With global production and supply capability for HexPly^® XF’s surface technology, as well as the option to customize the solution – for example in wind energy – HexPly XF for infusion can be produced with the first structural non-crimp fabric ply attached. Hexcel’s latest surfacing technology innovation can be adapted for a massive range of applications.”

Q: How easy is it to incorporate HexPly XF into the production process? We could perhaps imagine that some potential users who are not experienced with prepreg materials might be nervous about a prepreg material and its cold-storage requirements.

AF: “HexPly XF is a very robust prepreg system. Typically, no cold storage capability is required. Customers will require only temperature-controlled storage, which is normally required anyway to store widely used resin components. With an outlife of up to 6 weeks at ambient temperature, HexPly XF provides an easy-to-adopt solution, even for those not currently using prepregs.  With all of the material mixing and measuring done by Hexcel on the prepreg line, HexPly XF is potentially easier to use than a gelcoat, removing the chances of a mixing or application error. In addition, customers will not require investment for the mixing equipment required for gel-coat application.”

Q: How does the HexPly XF surface compare technically with a traditional polyester or vinylester gelcoat?  Does it provide a more durable surface?

AF: “There are several technical benefits to using HexPly XF as a surfacing technology.  Machine-produced prepreg materials are calibrated for thickness online, so not only is HexPly XF lighter than a gelcoat (typically 50% lighter per m² than gelcoat), but it is also more consistent than a hand-applied or sprayed product that is very operator dependent.  This completely uniform surface coating is particularly important in large wind blades, ensuring that weight distribution and balance are maintained, which is critical as rotor diameters continue to increase. The cured HexPly XF surface is also more durable than the gelcoat it replaces, and it minimizes print-through from the reinforcement layer. All of these improvements are achieved while also removing the liquid handling, exothermic reaction and harmful vapor hazards present with shop floor mixed and applied gelcoats.”

Q: From where do you forecast the key financial benefits coming if users are to switch to a HexPly XF solution for their component finishing? Is it purely a production time reduction in the finishing stages or are there other factors?

AF: “We developed HexPly XF to provide a better surface finish to finished composite parts but, of course, we had to demonstrate that it could be cost-competitive and also save time in the overall manufacturing process.  Blade manufacturers can save around 3-5 hours per blade (30-50 man hours) using HexPly XF in an infused blade, so the benefits are significant. HexPly XF’s roll format also means that dedicated mixing equipment used for traditional gelcoats (along with consumables like brushes and rollers) is no longer required. In addition, the working conditions on the shop floor are improved with no need for vented tents or spray booths to protect workers from hazardous fumes during gelcoat application. These additional indirect savings could provide a blade factory with annual cost reductions of up to €1,000,000.

HexPly XF provides our most technical surfacing solution, providing a high quality, pinhole-free, paint-ready surface straight from the mold, for a massive range of large infused or prepreg composite component applications.”

No gel coat needed: ready-to-paint surface & safer process