The spread of carbon composites in mass series applications has prompted a need to rethink end life and find new uses for recycled materials
The carbon fibre reinforced plastics (CFRP) are experiencing a second coming of age thanks to technological and market developments in two key sectors – aerospace, with the advent of the Boeing 787 Dreamliner (manufactured in part in Italy by Alenia Aermacchi), and automobile, with BMW launching the production of the i3 series, small cars manufactured in medium volumes, featuring a CFRP passenger compartment.
The mechanical properties and light weight of the materials are highly appealing to the transportation sector, where fuel savings need to be balanced with high passenger safety standards. Its success is easy to explain: replacing metals with composites can save between 20% and 40% in weight without significant loss in mechanical performance and only minimal limitations to the automation process.
This significant leap in volumes compared to the past on the one hand drives the development of increasingly fast, automated and economically-viable processing technology; on the other, it poses new challenges in recovering and recycling the materials used, especially in the automobile sector, where environmental appeal and stricter standards pose continual obstacles for styles centres in designing new models.
Thanks in part to increased consumption of CFRP, it is not hard to find carbon fibre scrap from manufacturing and, to a lesser extent, recycling, sold at a much lower price (as much as half) compared to virgin product, because it is classified as special waste and, as a result, it is very costly to dispose of. This has prompted manufacturers to reuse scrap in production, developing special formulas and plants in instances where they can identify final applications for reclaimed materials.
This is what the European research project CRESIM (Carbon Recycling by Epoxy Special IMpregnation) aims to do, sponsored by Life+, and whose partners also include the Italian Cannon group. Researchers are aiming to develop technology for processing composite materials derived from as much as 100% recycled carbon fibre, guaranteeing mechanical and aesthetic performance comparable, if not equal, to that of the virgin material.
Research in Italy
As part of the European project, Cannon has the task of developing two processes suitable for impregnating different types of reinforcements in recycled carbon fibres, characterising such parts and developing applications that might have not only a place in purely technological terms, but also deliver economic benefit. One of the researchers’ tasks is to formulate highly reactive resin for demoulding finished parts within 200-300 seconds after impregnation.
The research is being conducted in Cannon’s R&D Center for Composites in Caronno Pertusella (near Milan, Italy), following installation of a high tonnage press fitted with large high-temperature platens. In the future, the machine will mount moulds supplied by clients for application development tests.
The station incorporates two 6-axis anthropomorphic robots, who handle recycled fibre reinforcements and control the mixing heads used in the closed mould injection or open mould laydown stages. The polyurethane-based reactive resins or the epoxy resins are handled by two instantaneous high-pressure and low-capacity Cannon blenders operating in fully self-regulated mode and closed-loop electronic control.
Two impregnation techniques
Cannon has used its experience in the field of short stroke and injection-compression presses to perfect two different methods for the open-mould impregnation of recycled carbon fibre mats:
• Estrim SLD (Spray Laydown): the epoxy resin is sprayed by an airless system, applied in a flat and triangular pattern directly on the surface of the fibre reinforcement, covering every square centimetre and using only the quantity of liquid required for the different parts of the finished piece.
• Estrim LLD (Liquid Laydown): the epoxy formulation is laid over the carbon fibre mat in liquid films, of varying width, typically from 40 to 120 mm. This technique almost entirely prevents any air from being included during impregnation, even in the case of large pieces. The carbon fibre reinforcement is preformed to the structure – generally with slight relief, 3D layer – of large car parts such as roofs, engine hoods, underbody parts, fenders and doors.
Satellite dish for mobile TLC
The first industrial results of the CRESIM project were recently showcased at JEC in Paris, the European composites show, where Cannon exhibited a satellite dish produced by Loson (based in Rescaldina), a manufacturer of carbon fibre reinforced parts for civil and defence purposes. Also collaborating in the project were Ferrari Carbon from Milan, supplying the recycled fibre, and DMC from Carate Brianza, which designed and made the moulds. The satellite dish, designed to be assembled in the field for civil or military communications, consists of seven equal parts and has an overall diameter of 130 cm. It can be transported in a large backpack and assembled in just minutes at the site of operations.