Overview
Composite materials offer the designer the ability to manufacture lightweight structures coupled with high strength/stiffness and excellent corrosion resistance. Composite materials are widely employed in the manufacture of work and leisure boats. However, these composite materials are predominantly based on room temperature curing resins such as polyester, vinylester, etc., which emit a solvent during processing and are difficult to recycle.
In recent years, the same materials have been increasingly used for road vehicles such as cars, trucks and semi-trailers. The key problem addressed by this project is the manufacture of large surface area structures (e.g. boat and semi-trailers) utilising liquid thermoplastic composite resins, which contain no solvents and which polymerise within the mould to form high performance environmentally stable structures that have better results over conventional thermoset resins. These thermoplastic structures are easier to recycle into short fibre reinforced components for reuse across a wide range of industries.
European dimension of the problem
According to the EUROPA website, within the EU 44% of goods are transported by road. Road traffic contributes to 23% of EU CO2 emissions (2006) and is expected to rise in 2010. In 2001 road freight travelled 1395 billion tkm and emitted CO2 at a rate of 0.178 kg/tkm. The composite trailer produced on this project is expected to deliver 10% (~1.5% from weight and 8.5% from aerodynamics) CO2 and directly proportional fuel savings. If all freight within the EU could realise efficiencies of 10% then a total CO2 saving of 24 831 000 tonnes could be made.
The strategic objectives were to provide sustainability in the European transport and other manufacturing sectors through:
- The development of advanced composite materials that are:
Thermoplastic; tough; durable; emit no VOCs; have a high strain to failure; have excellent fatigue, impact, water and chemical resistance; have high fibre volume fraction and thus can reduce component mass; have low density and high specific mechanical properties; are low cost and totally recyclable.
- This novel high volume fraction thermoplastic composite material will be used to produce complex components using new manufacturing processes that enhance sustainability through:
Emitting no volatile organic compounds and improving safety through component and design integration; production of high quality structural products that will reduce component weight, consumable, fuel and energy consumption and greenhouse gas and toxic emissions; enabling a cleaner manufacturing environment through the use of inert, dry resins; automating the manufacturing process and reducing the cost and complexity of tooling whilst increasing their flexibility and functionality.
Detailed product specifications for a 13.6m flat bed semi-trailer and an 8m boat hull formed the focus of the project against which the developed thermoplastic composite case study applications were measured. The low melting point and low viscosity thermoplastic PBT oligomers were then developed. These compounds included the catalyst, pigmentation and fire resistance compounds. The PBT oligomers were supplied in a form suitable for incorporating with continuous fibre reinforcement fabrics. All the necessary fibre-coupling agents and sizes necessary to achieve good fibre-resin interfacial strength were developed, as well as techniques to incorporate the PBT oligomers into the fibre fabrics for ease of handling and use during processing trials.
The optimum processing windows (time, temperature, pressure) and process conditions for achieving good wet-out of the fibres and low voidage were successively determined, as well as the mechanical properties of test laminates moulded under optimum conditions. These data were used to design the 13.6m semi-trailer and 8m boat hull. In order to validate the design, critical sections of the semi-trailer and boat hull were moulded and tested (critical sections include measuring the pullout strength of inserts and joints, etc). Having determined a design, prototype moulds for the semi-trailer and boat hull was produced. The semi-trailer and boat hull case study structures was manufactured and tested. Throughout the course of the project, techniques to recycle and reprocess all the thermoplastic composite materials produced during all the various processing steps (including the final moulded parts) were developed.
Funding
Results
Project's actual outcomes are:
- A novel thermoplastic resin was developed which allows the manufacture of high volume fraction components through modified versions of the traditional moulding processes of RTM, VI and vacuum bag moulding.
- A novel thermoplastic composite 'pre-preg' was developed and used to produce very large, complex components.
- Traditional moulding procedures were modified to accommodate this novel material resulting in enhanced manufacturing procedures, where dry inert raw materials are used, there are no harmful VOC emissions and the use of hazardous chemicals is vastly reduced.
- Improved product sustainability though employment of durable, corrosion resistant materials that increase product life cycle and can be recycled into new products at the end of life.
- Reduction of green house gas and fuel usage in the road transport sector through employment of weight saving high volume fraction composite materials.
- Design & manufacture of a 13.6m fully functional PBT composite, flat bed, tri-axle, semi-trailer.
- Intelligent tooling manufactured that allows for complete freedom in axle-configuration (ie position and number).
- Trailer geometry that provides; improved aerodynamics; structural rigidity (ie 2nd moment of area); and a vertically stackable shape allowing multiple trailer chassis to be manufactured in batches and stored/transported in a single trailer foot print before fit-out.
- Manufacture of a lightweight 5m Dory boat hull combining PBT composite and other recyclable thermoplastic composite materials.
Technical Implications
This project has brought together the wide range of technical and industrial skills required to economically produce high volume thermoplastic composites. These skills have been implemented to produce the world's first recyclable composite semi-trailer. Four of the partners will continue with further research in the applications and processing of PBT composites, and use this to develop sustainable products in the future. Two of the partners will continue to promote the composite semi-trailer concept and potentially develop further advanced prototype and eventually commercialised products.
Policy implications
Completion of this project and dissemination of the results will provide legislators and policy makers with evidence that technical solutions exist for more stringent emission regulations, and tougher end of life vehicle directives to be applied to the road transport sector.