Aspects of the use of composite materials in the manufacture of the external walls of internal combustion engine were studied. Costs were lower than expected, suggesting that large scale manufacture would be comparable to, or even better than the cost of making conventional engines. However, the technique for bonding alloy to plastic composite must still be improved. This deficiency caused oil leakage during the 200 hours of durability testing.
Testing also showed direct benefits in several areas. A fibre-reinforced plastic engine with alloy casing is lighter, cheaper to produce, makes less noise and warms up faster than a conventional aluminium engine. The engine uses 5% less fuel and produces up to 20% less hydrocarbon waste than traditional engine constructions.
The plastic composite structure for a composite engine was made in 3 sections and did not include any part of the engine cooling system. Future steps will attempt to combine the composite parts and extend their use to the outer surface of the water jacket.
The main hurdle in the design of the block structure was to fasten the plastic composite structure to the central alloy core. The method chosen was a combination of bonding and boiling, with metallic reinforcing and load transfer plates used in the known high-load areas.
A plastic composite rocker cover and oil pan were produced as direct replacements for their conventional counterparts. These parts were included in the project to monitor performance, material and manufacturing issues of composite.
A fibre-reinforced plastic composite internal combustion engine has been developed with the following characteristics:
The engine produced the same power torque as the all metal version.
Testing indicates a potential for up to 5% improvement on fuel economy. The composite warms up more quickly, reaching its efficient running conditions sooner.
Faster engine warm up time means that the heating system is effective sooner after starting, improving passenger comfort and defrost.
Testing of the new engine against an identical all metal control version showed a 3.1 dBA reduction in the maximum average noise levels. The new material has good damping characteristics.
The project engine weighs the same as its all metal counterpart. It is anticipated that a fully developed design will achieve savings of 10% over a conventional aluminium block, and 30% over cast engines.
A fibre reinforced plastic (FRP) composite internal combustion engine has been designed, manufactured and tested. The aims of the project were 3 fold: to investigate the advantages of introducing plastics to engines, to develop FRP materials for stressed components and the specific application requirements of the automotive industry, and to develop the high volume manufacturing technology for tooling the finished part production of complex and realistic FRP components. Recycling issues and the potential applications to internal moving parts were not within the scope of this project.
Some of the potential benefits of introducing FRP to engines are reductions in weight, noise, vibration and harshness (NVH) and the time to warm up from ambient conditions. Knock on benefits would include reduced levels of exhaust emissions, improved fuel economy and faster vehicle heater response from cold. Volume production studies investigated the effect of injection moulding parameters on process cycle time and moulding quality. They also developed the processes for preform manufacture in terms of forming base sheets, cutting and robotic handling. In parallel, a process parameter investigation of resin transfer moulding and a flow chart of production process flow were made. These enabled accurate cost studies of the complete engine block to be made.
A fibre reinforced plastic (FRP) composite internal combustion engine has been designed, manufatured and tested. The engine design was based on an assembly of 3 FRP components bonded to a skeletal aluminium casting. The FRP components were produced by injecting epoxy resin into random glassfibre preforms positioned in a low cost electroform moulding tool. The skeletal metal core retained the combustion chamber, cylinder, bearing, cooling and lubrication features. A composite oil fan and valve rocker cover were manufactured to investigate new reinforced materials and prototype tooling concepts. The FRP engines produced underwent thermal analysis, durability and noise, vibration and harshness (NVH) evaluation. The engine warmed up 15% faster an demonstrated the potential for a 50% reduction in warm up time by the greater use of FRP. The engine completed a full durability test during which no failures of FRP related components occured. The NVH tests revealed that the maximum average noise levels were 3.1 dBA less than for an equivalent all metal engine. Tests indicate the potential for a 5% fuel economy improvement and a weight saving of 10% to 30% while producing the same power and torque as an all metal engine. There is also the potential for a 20% reduction in engine hydrocarbon exhaust emissions. Volume production in studies investigated the effect of injection moulding parameters on process cycle time and moulding quality. The processes for preform manufacture in terms of forming base sheet, cutting and robotic handling were developed. I on parallel, a process parameter investigation of resin transfer moulding and a flow chart of production process flow were made. These enabled accurate cost studies of the complete engine block to be made.
A specification for the glass mat reinforced resin for use in a fibre reinforced plastic (FRP) composite engine was supplied. The specification included:
basic mechanical properties;
long term behaviour;
On the basis of their anticipated properties, 5 different classes of resin were chosen:
In order to obtain a workable set of candidate resins for resting, one system from each class was selected (except for the unsaturated polyesters, where 2 were selected). This selection was done by comparing product data sheets. Test panels were manufactured using a standard Unifile continuous glass mat material as reinforcement and the following test programme was carried out:
flexural stiffness, strength and strain to failure determination at a range of temperatures;
impact properties determination;
residual compression strength after impact determination;
flexural property determination after conditioning in air, coolant and engine oil;
stress relaxation behaviour;
dynamic mechanical analysis in torsion;
flexural fatigue life determination.
On the basis of the results of the test programme, the following conclusions were formulated:
the epoxy composite provides the best overall property set although some questions remain with respect to its long term behaviour in hot, wet conditions;
the modified unsaturated polyster composite approaches the epoxy property profile when unconditioned but after conditioning in collant and oil its flexural properties are importantly affected;
the bismaloimid composite has a good property profile but suffers from collant and oil conditioning;
the phenolic, vinylester and unmodified unsaturated polyster composite do not meet the requirements.
Thus the epoxy resin, EPIKOTE 6007/6507, was selected.
An early study indicated that the most successful approach to the design of the overall engine structure would be to use a central core of conventional metallic materials and composite materials for the outer walls of the engine. It was decided to make the composite structure in 3 sections and to exclude the engine cooling system from these parts. The main challenge in the design of the block structure was fastening the composite structure to the central core. The method chosen was a combination of bonding and bolting, with metallic reinforcement and bad transfer plates being used in areas of known high loads. Various engine components were mounted directly to the composite structure:
auxiliary drive housing.
A variety of fastener options were chosen for these different tasks to enable their relative merits to be compared. These methods included through bolting, bolting into formed in phase and bonded inserts, and bolting directly into the composite material. A composite material rocker cover and oil fan were also produced. These parts were included to examine performamce, material and manufacturing issues. 4 engine block assemblies were produced. The thermal analysis engine was the first to run and initial testing revealed problems which had not been apparent during build, such as timing chain fouls, tensioner misalignment and oil leaks. Actions to resolve these problems were incorporated into subsequent engine builds. The engine was despatched to the University of Nottingham for thermal analysis. The second engine successfully completed a full durability test during which the composite panels were scanned with a dynamic stress analysis system. Analysis of the data showed the surface strains were low and that structural failure would not be invisaged. The third engine was used to evaluate the noise, vibration and harshness (NVH) characteristics. The maximum average noise were 3.1 dBA less than fo r a comparable metal engine. Several actions were taken to publicise and demonstrate the project, including the production of a video and the installtion of an engine in a Ford Fiesta.
The role of the Galvanoform Company was the design and manufacture of the nickel electroformed moulds for moulding component parts of the engine. It was decided to use the resin tranfer moulding (RTM) method in which resin is injected into a closed mould which contains a preform made of fibre. An electroformed mould can be no more accurate in size, shape and in surface finish than the bath master, which is the form onto which the nickel is deposited to form the mould. The bath masters were designed and manufactured by the National Engineering Laboratory (NEL). The manufacture of the moulds was done in line with Galvanoform is normal production processes. The moulds comprised a single layer of sulphanate nickel backed with a layer of copper to improve heat distribution and temperature control. The tooling eventually comprised 2 mould sets, each of 3 parts, on set for the inlet side and the other for the exhaust side, and a third mould for the front plate, which was cut in 2 parts from steel, so as to reduce delays. The mould sets were tested and could be brought together and closed to complete shut off without difficulty. However when, prior to moulding, the first preforms were placed in the moulds, unexpectedly high forces had to be used to bring the moulds together and some distortion and, thus, leaks occured. The cause of this problem was investigated and it appeared that the preforms were too thick for some of the mould cavities. Specific and close tolerances are necessary both in preform thickness and in mould accuracy and these should be related to volume fractions of preform to cavity.
Techniques for the manufacture of fibre reinforced plastic (FRP) engine block components on a volume production scale were investigated including:
preform cutting and handling;
The requirement for high volume production of components demands preforms which fit cavities precisely to inhibit preferential resin flow, therefore laser, water jet and ultrasonic cutting were investigated. Water jet cutting was found to be the best solution. Preforms may initially be preformed to shape such that their profile is only slightly longer than that intended to fit a tool cavity and the small amount of surplus could then be removed by a water jet cutter mounted in a robotic head. Complete preforms are likely to be built up from a number of smaller subpreforms. The use of a robot for building complete preforms has shown that with the use of vacuum techniques for handling the individual subpreforms, a preform can be assembled quickly and accurately into a tool. The various parameters of injection with hot setting epoxy resins were investigated and this work led to the development of a vacuum system for production volumes and development of a resin inlet valve which allows hydrostatic pressure to be maintained during curing yet eliminates all liquid and semiliquid resin in the area of the total injection point. Investigation work using a flat plate tool and a number of different parameter variations has enabled optimum cycle times to be assessed. Cycle times for an unaccelerated epoxy resin system were about 6 minutes. However tests on accelerated systems in the laboratory have shown that the above time could be halved. A full costing for a plant manufacturing 3 seperate components has been produced together with a plant layout.
The first activity involved the examination of the engineering drawings of the Ford LAMBDA engine with the objective of:
familiarisation with all aspects of the structure of the block casting and the nature and purpose of the associated engine components;
identification of those areas of the metal block that could be replaced by fibre composites.
A basic concept design was produced for a composite engine block that assisted of a metal core casting and 3 fibre reinforced plastic (FRP) moulded components, 2 sides and a front chaincase gallery. Detailed engineering drawings of the metal core casting and the 3 FRP mouldings were then produced. 2 moulds, one for each of the side mouldings, were to be produced by Galvanoform and this entailed that NEL machine 6 bathmasters to allow the electroforming of the 3 parts of each of these 2 tools. This work was beset by problems, particularly a distortion of the bathmaster when it was removed from the machine after the main cutting of the details had taken place. The solution to this problem involved mounting the unmachined slab for the bathmaster after on a steel backing plate. It was decided to manufacture the tool for the chaincase moulding by a more conventional machining route. Detailed drawings were produced for the 4-part moulding tool and it was machined from an aluminium alloy. The chaincase moulding was then manufactured. This involved the progressive development and improvement of a complex preform in Unifilo mat and after extensive preparatory moulding trials, a final moulded component design was produced. A survey was undertaken of the suppliers of sealants and adhesives to identify candidate materials for the assembly of the composite block. In the event, Loctite were invited to advise on these aspects and to supply a suitable system. The actual assembly and bonding of the 3 FRP components to the core casting using the selected adhesive systems was then completed.
In order to investigate the thermodynamic performance characteristics of a fibre reinforced plastic (FRP) composite engine, an experimental facility was established. This consisted of an engine dynomometer installation with requisite instrumentation for performance monitoring linked to a microcomputer data logging and processing system. Also a theoretical 2-dimensional finite difference model of a transverse engine section was developed to investigate how design features dictate local temperatures and heat flow in the engine structure. Theoretical and experimental engine warm up investigations showed that the use of FRP material reduced the effective thermal capacity of the engine block, leading to engine warm up times which are typically 12% less than for a conventional engine. The steady state performance of the FRP engine is very similar to that of a conventional engine. The most severe thermal operating condition was established to be at maximum power. Temperature distributions throughout the engine were determined at this condition by a combination of theoretical and experimental studies. FRP joint temperatures were found to be 100 C to 120 C, demonstrating that the engine design was satisfactory with regard to the exposure of FRP to high temperatures. The scope for the increased exploitation of FRP materials was investigated using the theoretical model. The deployment of FRP materials is limited by metal to FRP joint temperatures. These temperatures can be reduced with an alternative coolant passage design. Cooling system design must be addressed at an early stage in the design of engines with a high FRP content. Theoretically the volume of the metal core component could be reduced by approximately 45% giving a predicted reduction in warm up times in the order of 50%
This project involved the production of the external casing for an engine block of fibre reinforced plastic (FRP) composite material. The production technique employed was resin transfer moulding (RTM), the reinforcement of which was provided by glass fibre which was preformed to the shape and dimensions of the moulded part. The 2 side parts of the engine block, the exhaust side and the inlet side, were produced. First, the bathmasters which had been made by the National Engineering Laboratory were used as a patton to make the preform tools. The side panel preforms were then constructed from a number of seperate subpreforms. To produce one of these subpreforms a number of layers of Unifilo continuous filoment mat were placed together and heated to a temperature of 120 C. They were then pressed between the preform tools and allowed to cool. The excess glass around the preformed shape was trimmed away to leave a stable preform of the correct size. 2 of these thin panels were placed back to back, the flange area at one end of the component was built up from a seperate subpreform while small thicker areas were constructed with suitable pieces of thicker preform material. In all, 6 subpreforms were used to make the exhaust side preform and 8 for the inlet side. These preforms were then placed in the moulds which had been produced by Galvanoform and the liquid resin (EPIKOTE 6007) containing the reactive hardening system was injected into the sealed moulds. Thus, 9 exhaust side and 9 inlet side panels suitable for use as engine block components were produced. As part of the preliminary investigations, a series of flexural fatigue tests were carried out by Vetrotex. 6 resins reinforced with Unifilo glass mat were tested and the epoxy resin, which was subsequently chosen for use, was found to be the best.
THE OBJECTIVES OF THIS PROJECT ARE:
- TO USE FIBRE REINFORCED PLASTIC COMPOSITE MATERIALS IN AN ENGINE DESIGN TO ACHIEVE DIRECT AND INDIRECT FUEL ECONOMY SAVINGS, NOISE, VIBRATION AND HARSHNESS (NVH) IMPROVEMENTS, FASTER WARM UP AND COST SAVINGS;
- TO RESEARCH AND DEVELOP THE MATERIALS TECHNOLOGY FOR POTENTIAL FUTURE MANUFACTURE OF SIGNIFICANTLY LIGHTER AUTOMOTIVE SPARK IGNITION ENGINES BY THE USE OF FIBRE REINFORCED PLASTIC COMPOSITES;
- TO DEVELOP PROCESSES AND TECHNIQUES TO SUPPORT THE MASS PRODUCTION OF PLASTIC COMPOSITE COMPONENTS.
Funding SchemeCSC - Cost-sharing contracts
WV4 6BW Wolverhampton
G75 0QU East Kilbride