Lightweight Composite Monocoque Heavy Goods Vehicle Trailer

ROADLITE - Manufacture of a lightweight, cost effective, polymer composite road trailer* Matthew Turner


Gerry Boyce 




This paper describes the design, development, manufacture and testing of a lightweight polymer composite Heavy Goods Vehicle (HGV) trailer with the ability to produce flatbed, curtain-sided and boxed trailers. New modelling concepts have been developed to aid the vacuum infusion (VI) of a novel composite monocoque trailer using commercial grades of composite materials to keep cost at a minimum. A mixture of conceptual design, Finite Element Analysis (FEA), prototyping and testing has resulted in the manufacture of a 10 metre composite trailer weighing almost 400 kg less than a conventional steel unit. This equates to a 20% reduction in weight of the steel chassis. Testing has, so far, successfully proven the concept and integrity of the design and has shown benefits of 18% increase in stiffness, 20% reduction in mass and a reduction of 398kg of CO2 per year compared with conventional steel trailers . Key Words: Roadlite, composite trailer, lightweight trailer, polymer composite, transport, HGV 1 Introduction 

•

Road haulage is by far the most important form of transport for

To examine and specify the most appropriate type of processing and materials to be used in the construction

goods in Europe and is expected to grow by 25% over the next 15 years. This growth is in conflict with the environment as 87% of



of the trailer. •

To manufacture and assemble a prototype composite

all goods and freight are transported by heavy goods vehicles (HGV),

HGV for extensive evaluation trials on a test track to

in particular semi-trailers. This accounts for approximately 10% of

quantify its operating performance and functionality.

the total European energy consumption and contributes over 30% of total CO2 emissions as well as producing many other pollutants and causing damage to roads and bridges. As vehicle weight accounts for a significant proportion of fuel consumption and CO2 emissions, the use of lightweight materials and construction techniques are becoming increasingly important.

2 Design 

Market research showed that a 10 m urban articulated trailer was the most appropriate case study due to its need for weight savings. The study also showed that a high proportion of HGV trailer sales

The overall aim of the Roadlite project was to research, develop

are curtain sided (rather than box), and the decision was made to

and demonstrate the manufacture of a new lightweight, aerodynamic,

design a stand-alone chassis onto which different bodies could be

composite, multi-functional semi-trailer to replace the current heavy

attached.

(and labour intensive) fabricated trailer design. In order to design a suitable composite trailer it was first Major objectives of the project included: •

To compute an HGV design, which is lightweight,

chassis that would be replaced. The design of steel trailers to date

aerodynamic and multi-functional (i.e. capable of being

has been a largely empirical process and it was therefore necessary

used as a boxed, flatbed or curtain sided trailer).

to generate the data through analysis and testing.

*Presented at 2005 JSAE Annual Congress 

1) 2 Europrojects LTTC Ltd, 1-3 Fowke Street, Rothley, LEICS, 

necessary to establish the properties and performance of the steel



Firstly, a global stiffness for the standard steel structure was

LE77PJ, UK

calculated. Accelerated dynamic testing was then performed at

E-mail;[email protected]

Leyland Technical Centre (LTC) on their test track. Data from

Web: www.europrojects.co.uk

strain gauges and accelerometers was used to gain insight into the

reaction of the trailer to load in different dynamic situations. The

The design was also modelled by FEA to predict any areas of

final part of the assessment, FEA, was used to validate the test data

concern. A CAD model of the final design is shown in Figure 2

and highlight potential problem areas. Figure 1 shows a screen

below.

shot from the simulation, and it can be seen that one area of high stress occurs at the Goose Neck.

Fig.1 FEA of steel trailer Fig.2 CAD model of underside of composite trailer The outputs of this test data were used to design the composite structure which evolved from design inputs relating to a range of 3 Process Development and Flow Modelling

loads (static, dynamic and deck load).



Very early on in the project it was known that, in order to achieve One of the advantages of composites compared with steel is that

good results and fulfil the required objectives, the composite

the product is produced in a mould and so the depth and thickness of

manufacturing process must be fast, simple and cost effective and

material can be tailored so that the rigidity and strength of the system

yet create composites with consistently reproducible high levels of

matches the operational requirements at any particular position.

mechanical properties. In order to achieve this for large structures, the vacuum infusion (VI) process was chosen as the manufacturing

To compete in terms with cheap steel fabrications, commercial

route.

grades of E-glass and polyester resins were chosen as the composite materials. A monocoque-style concept was designed because it

The main problem with VI was that because it is a one-shot

used the material properties to their maximum benefit. Using the

process, the manufacturer must know, without doubt, that once the

material to its best advantage, the shape of the monocoque was

process is started, the resin will fully infuse and wet-out the fibre

therefore altered to provide stiffness where it was required. This

reinforcement. The University of Nottingham (UoN) investigated

was achieved by changing the section of the trailer in three key

the parameters that affect the infusion process and worked on a

positions: the front section governed by the ISO Gooseneck profile

model to predict the overall infused geometry, time to infuse, and to

and the need for a specified deck height; the mid section which

help in the location of inlet and outlet ports to produce a faster or

carries the majority of the bending load and so is made more rigid;

more consistent moulding.

and the rear section which is governed by the suspension space envelope and transverse loads rather than bending. A mixture of CAD and CAE were used to design the composite structure.

The final design incorporated longitudinal beams to

transfer load; sandwich components; transverse webs to take suspension loads; steelwork for attaching the suspension and legs; attachment points for the kingpin and fifth wheel; load bearers in the shallow front; composite under-run devices and steelwork front and rear to enable attachment of different body styles. Traditional steel legs, suspension and ancillary running gear were designed into the system so that maintenance would not be a problem.

Fig.3 CAD model of underside of composite trailer

The permeability of the different reinforcements and infusion media were tested and input into a computer model that was

A gel coat layer was applied into the mould to protect the

specially developed by the University of Nottingham to determine

underlying laminate and provide a good aesthetic surface finish.

the flow front of the resin during injection. Figure 3 shows a

The dry glass fibre reinforcement was then laid into the mould

simulation of a part of the trailer during infusion.

according to the structural design and the drape analysis. A nylon peel ply fabric was laid over the reinforcement to provide a release

The modelling or “forecasting tool” was developed with the intent of allowing integration in an automated control system that would

surface and finally a polypropylene infusion mesh and vacuum bag were applied.

actively ensure that the ideal flow patterns were followed. Conceptually an active control system can use the flow models to

A sequential infusion strategy was adopted which allowed

compare the actual flow patterns to the ideal, forecast the effect of

controllable permeation through the thickness of the laminate. The

different control actions on the flow pattern and, opting for the one

process (shown in Figure 5) was very successful and took an

which better reproduces the ideal situation, act on the mould to steer

accurately predicted eighty minutes to complete.

flow. Work to develop this automated mould filling tool continues. The UoN also developed a drape analysis tool to determine how the fibre reinforcement fills (or drapes into) the tool. Best surface lay-up was determined as well as dimensions of the net shapes to be cut. Four main patterns were necessary to cover the mould surface while minimising overlaps and reinforcement cutting.

4 Manufacture 

To construct the mould tools, a number of cross section computer aided design (CAD) drawings were produced to create profiles that were laser cut from MDF and mounted onto a base, as shown in Figure 4. Wooden battens were secured into the sections and MDF

Fig.5 Main body is infused with polyester resin

sheet was attached to the battens to provide a mould surface. To complete the mould tool, four coats of epoxy primer and six coats of epoxy high-build paint were sprayed onto the surface. This had the effect of sealing the porous MDF, stabilising the surface and providing a smooth gloss finish to aid release of the part from the mould tool.

All of the individual mouldings were joined together to form the trailer and then the ancillary components such as suspension (tandem axle), landing legs and pick-up plate were attached. The final trailer can be seen in Figure 6.

Fig.6 Composite trailer Fig.4 MDF mould during construction

5 Testing

and exhibited no unusual behaviours.



The trailer was tested at LTC, Leyland, UK. The weight of the trailer was 3740 kg, representing a 9.4% (390kg) reduction compared to the benchmark steel trailer.

Maximum static

Strain measurements showed the bending stiffness of the composite trailer to be 18% higher than the steel trailer. Analysis

deflection under full UDL of 23280kg was just 6mm and

of strain data confirmed the visual and video assessment of the

represented an in crease in stiffness of 18% compared with the steel

stability of the load bed, with maximum dynamic deflections of less

trailer.

than +/-5 mm.

This strain data also confirmed that the main

structure was operating well within its strain limits and should Strain gauges were applied to the trailer and strain was measured

therefore suffer no major fatigue problems in service.

whilst the laden trailer completed various manoeuvres and crossed various typical road features. Analysis of the strain data revealed

Given the high stiffness of the composite trailer there would

that the amount of dynamic deflection during these tests was very

clearly be the opportunity to reduce weight further, with a clear

low at a maximum of +4.1mm/-3.5mm compared to the static

potential to reduce fuel consumption, and hence carbon emissions by

deflected shape. The strain data, which was measured at the point

up to 2%.

where maximum strains were expected, showed very low levels of both static (733µE) and dynamic (+1410µE /+338µE) strain for the material and it was obvious from the tests that the trailer was lightly stressed. As a consequence, fatigue failure of the main structure ACKNOWLEDGEMENTS

would be extremely unlikely in service.

This project has been jointly funded by industry (Euro-Projects LTTC Ltd {EPL}, VT Group, LTC Ltd and Southfields Ltd), the 6 Conclusions 

UK Department for Transport and the Engineering and Physical

A 10m urban articulated trailer has been designed as a stand-alone

Sciences Research Council under the LINK Foresight Vehicle

polymer composite chassis onto which different bodies (box or

programme. This programme aims to foster relationships between

curtain sided) can be attached. This design provides a great degree

industry and academia to create components and systems for the

of flexibility in the number of end uses and also utilises the weight

vehicles of the future.

advantages effectively.

The trailer design is based around a

monocoque structure, thus maximising the flexibility of the composite materials in reducing weight. New modelling concepts have been developed to aid the vacuum infusion (VI) process and the trailer has been manufactured using commercial grades of composite materials to keep cost at a minimum.

A mixture of conceptual design, Finite Element

Analysis (FEA), prototyping and testing has resulted in the manufacture of a 10 metre composite trailer weighing almost 400 kg less than a conventional steel unit. This equates to a 20% reduction in weight of the steel chassis. Considering an average train weight of the tractor and trailer with load of 12,740 kg (i.e. a 5T tractor with a 4T load on the trailer), the overall weight saving would be 3%. Typically, this would equate to a fuel saving of around 1.5% on an urban/local delivery duty cycle. A reduction of 400kg in a vehicle travelling 100,000 miles a year equates to approximately 398kgs of CO2 each year per vehicle Testing on the proving ground over a variety of surfaces and with various vehicle manoeuvres showed that the trailer was very stable