Nearly all the advocates of fibre reinforced polymers (FRP) shy away from talking about the many elephants in the room and there are enough of them that is beyond crowded. IDTechEx
do not see these downsides as insurmountable barriers and instead look at the problems as opportunities and hotbeds of innovation.
This article will highlight the downsides and some of the most promising technical solutions for FRP parts. For detailed analysis, including company profiles and full supply chain assessments for synthetic and natural fibres, see the primary-interview led report from IDTechEx - "Composites 2017-2027: Innovations, Opportunities, Market Forecasts
Cost and manufacturing
The first, and most obvious, thing to state about composite parts is that they are too expensive and that the manufacturing is not quick or easy.
For the more expensive fibres, such as carbon, the cost will gradually come down both as the scale and associated infrastructures increases and manufacturing costs are reduced. Plasma oxidation ovens, from 4M and Teijin, will start to be used in the near-future and provide a more energy efficient process. These improvements will allow the heavy tow carbon fibre variant to creep towards the much-quoted $5/lb threshold - the apparent gateway to higher successes.
Stepwise changes in the cost could occur for carbon fibre through alternate feedstocks. This includes the use of PAN-textile that came out of ORNL
and is being commercialised by LeMond composites, the potential for a lignin precursor
and alternate routes to mesophase carbon pitch from Advanced Carbon Products
. Although these are still a way from being out of the pre-commercialisation stages and the potential property variations have yet to be fully established, they remain ones to watch closely.
As was discussed in a previous article
, manufacturing FRP parts is multi-faceted and there is a constant pressure to increase the speed and automation, allowing for higher volumes and a deskilled workforce. Variations of the classic RTM and compression molding are ever present and fast-curing resins are constantly being improved so as to not be the limiting factor.
Automated robotic arms have been used for a long time and hold advantages including reduced wastage, skipping sections of supply chains and sophisticated versatile design strategies. The fibre patch placement from Cevotec (photo) or the roving applicator from Voith
demonstrates that there are many progressive steps in this industry.
Fibre Patch Placement from Cevtotec (left) and compression molding with induction heating from RocTool.
Source: IDTechEx and RocTool.
There are multiple physical and chemical property advantages with FRPs, but no fibre comes without serious limitations; the most common being poor impact resistance, no vibrational dampening, and moisture absorption. Research does go into improving these, mostly through post-synthesis processing, but the more realistic next step is utilising hybrid parts.
One solution is to combine two different fibres to benefit from their individual properties; some notable examples include the use of UHMwPE (branded Dyneema) from DSM
or using basalt mineral fibre (branded Filava) from Isomatex both in combination with carbon, primarily to improve impact resistance and in the latter example to also reduce cost.
The other strategy is to use the composite part in combination with something else entirely. This can involve joining the part with a dissimilar metal and minimising the use of the composite to only where it is required. Adhesion-free joining through chemical processes or laser ablation from companies such as MEC
group and Daicel
, respectively, have been gaining increased attention in this area. Alternatively, the part can be overmolded with a thermoplastic, and manufacturing techniques like the FiberForm technology from KraussMaffei have helped facilitate this.
Breakdown by type of core material used in a composite sandwich part.
Sandwich parts and fibre metal laminates have been exploited for a reasonable while, but there is still lots of room for innovations and large changes. For the sandwich core, the main types are foams and honeycombs, but there are smaller categories such as balsa wood and resin-infused variants. IDTechEx predict foams to get a greater share of this growing market over the next 10-year period. This is largely down to the additional properties they can provide for the larger growth markets (notably energy and automotive sector) and significant innovations. Examples of these innovations include the in situ foamed PMI called ROHACELL from Evonik
, stiff PET foam produced from waste bottles from Armacell, and new foaming techniques that allow different materials, such as nylon, to be foamed from Zotefoams.
An important area to consider is how these composite parts are repaired. The difficulty here is not only that viable solutions need to be found, so that confidence in their structural integrity can be assured, but also how the associated infrastructure must change to accommodate this. It is not reasonable to assume that a click-out-and-replace strategy is going to be satisfactory for the long-term.
There are emerging solutions to this, such as research from DLR involving an inductive
heating patch, portable in a suitcase, is beginning commercialisation shortly and the ongoing Composite Adaptable Inspection and Repair (CAIRE) project is making progress. Even further ahead and still at the early university research stage, is the exciting opportunity for self-healing structures primarily using vascular networks or embedded microspheres.
As volumes increase to substantial levels and first-generation high-volume products begin to be retired, the question arises as to what happens at the end of their functioning life and how can the environmental impact of manufacturing processes be minimised. Life Cycle Assessments (LCA) is the phrase on most people lips within this industry right now.
One solution is to improve the recycling, there is approximately 24,000 tpa in CFRP waste every year and approximately half of this comes from prepreg off-cuts. The most viable recycling solution to date is pyrolysis, but there are others that may have potential. ELG Carbon Fibre are the leaders in recycling CF and are planning on dramatically increasing the number of pyrolysis plants from 1 to 4 before 2025. This ramping up is important as the market will get crowded quickly, and in the future this large surplus of waste may not satisfy everyone's needs. Carbon Conversions and Vartega are the most promising start-ups, the former having gained investment from Hexcel
, but young companies are not alone as large players start to turn their hand to this field.
The LCA can be taken a step further by considering the complete manufacturing process, this is mostly driven by economic advantages with the environmental impact as a bonus. As discussed earlier, the use of robotic arms minimises the wastage of fabrics or prepreg material and similarly, the use of reusable vacuum bags, such as those developed by Alan Harper Composites, are gaining traction for the same reason of minimising waste.
Repair kit in a briefcase from DLR with induction patch attached to a wind turbine in the background (left), recycled CF contribute to the iStream from Gordon Murray Design (centre), chopped flax fibre composite in aerospace dolly cart (right).
and Gordon Murray Design.
Biosourced resins are an important step and remove the impact of their petrochemically-sourced counterparts, but fully biodegradable is another and the greater goal. Pond, who use starch-based feedstocks, and Arctic biomaterials, developing biodegradable glass fibres embedded in PLA, are just two examples of promising innovative companies in this field. Although the market may not be economically ready right now the high-volume end-users are circulating with intent, particularly if anticipated legislation demands makes these the only viable solutions.
Finally, natural fibres obviously lend themselves nicely to this cause and there is substantial growth expected. The most excitement is around the family of bast fibres, which IDTechEx anticipates having a market value exceeding $140m (for the fibres in composite parts) by 2027. The role of flax and hemp are the main materials, and as an example of the new markets these are entering an image of an aircraft trolley cart as manufactured using short flax fibres by ecotechnilin is displayed.
To find out more about all these innovations, companies and market dynamics see the new report on "Composites 2017-2027: Innovations, Opportunities, Market Forecasts" at www.IDTechEx.com/composites