The use of alternative materials for sideguards · 2020. 11. 4. · TRL is committed to optimising energy efficiency, reducing waste and promoting recycling and re-use. In support

The use of alternative materials for sideguards

by G J Couper

UPR SE/084/04 S0131/VE

UNPUBLISHED PROJECT REPORT

TRL Limited

UNPUBLISHED PROJECT REPORT UPR SE/084/04

The use of alternative materials for sideguards Version: Final

by G J Couper (TRL Limited)

Prepared for: Project Record: S0131/VE Integrated Spray Suppression and Safety Guards for HGVs

Client: VTS 7 Division, DfT

Copyright TRL Limited August 2004 This report has been prepared for the Department for Transport, Vehicle Technology and Standards division (VTS) is unpublished and should not be referred to in any other document or publication without the permission of VTS. The views expressed are those of the author(s) and not necessarily those of VTS.

Approvals

Project Manager

Quality Reviewed

This report has been produced by TRL Limited, under/as part of a Contract placed by the DfT. Any views expressed are not necessarily those of the DfT. TRL is committed to optimising energy efficiency, reducing waste and promoting recycling and re-use. In support of these environmental goals, this report has been printed on recycled paper, comprising 100% post-consumer waste, manufactured using a TCF (totally chlorine free) process.

CONTENTS

Executive summary i

1 Introduction 1

2 Strength requirements 2

2.1 Current requirements 2 2.2 Vehicle collision strength requirements 2

3 Current sideguards 4

3.1 S050G/VE Report 4 3.2 TCIS database 6 3.3 Current materials 7 3.4 ‘Typical’ guard 7

4 Investigation of material alternatives 8

4.1 Steel 8 4.2 Aluminium alloys 8 4.3 Advanced metals 9 4.4 Glass Fibre Reinforced Plastic (GFRP) 9 4.5 Advanced composites 11 4.6 Sandwich construction 12 4.7 Recycleability of materials 13 4.8 Cost considerations 14

5 Weight comparison 16

5.1 Current guard weights 16 5.2 Guard deformation 16 5.3 Different strength requirements 18 5.4 Different guard dimension 19 5.5 Non-structural panel guards 20

6 Integration of side and rear protection 21

6.1 Material compatibility 21 6.2 The effect of integration on strength and weight 22

7 Alternative trailer designs 23

7.1 Krone Safeliner 23 7.2 Roadlite 24 7.3 Composit Trailer 24

8 Discussion 26

9 Conclusions 29

References 30

TRL Limited UPR SE/084/04

TRL Limited i UPR SE/084/04

Unpublished Project Report Version: Final

Executive summary TRL was commissioned by the UK Department for Transport (DfT) to investigate the potential benefits of an integrated approach to the design of safety guards and spray suppression equipment for HGVs. The project aims to identify and quantify the potential benefits of an integrated spray suppression and underrun protection structure. In particular the project will aim to assess:

• Safety benefits to vulnerable road users through improved sideguards

• Safety benefits for all road users through reduced spray

• Cost and environmental benefits through improved fuel economy resulting from improved vehicle aerodynamics

As part of this work the project aims to develop a test method for quantifying whole vehicle spray that could be used as a regulatory test.

The project has been split into three modules in order to reflect the above objectives. This report has been written as part of the module of the project studying the potential benefits of improving the underrun protection through improved integration. This report considers the materials currently used in safety guards and identifies alternative materials that could be used in future designs. Materials are assessed based on strength requirements, weight, cost, recycleability and suitability to this application.

Assessment of the weight of a ‘typical’ guard constructed from different materials is used for comparison. The weight penalty of increasing the guard size and strength requirements is investigated.

The main conclusions of the report are presented below.

Comparing a guard that is minimally compliant to the UK regulations with the ‘typical’ guard currently fitted to an HGV shows that current guards are designed to be stronger than required by regulation. This suggests that guards currently fitted are heavier than is necessary.

CFRP is the only alternative material identified that offers a significant weight saving over steel. Based on the material properties assumed in this report, guards constructed from CFRP were 63% lighter than the steel equivalent. The weight saving is more considerable if the strength or size requirements of the guard are increased. By using CFRP it is possible to construct a guard that can withstand a perpendicular vehicle impact at 56km/h which weighs only 23% more than the ‘typical’ steel guard currently fitted to HGVs.

The exact CFRP materials need to be carefully selected to give impact and durability properties as well as strength. Aramid and carbon fibres can be used in combination to prevent brittle failure or damage under low energy impacts such as during loading operations.

The other alternative materials considered were unable to provide a significant weight saving over steel for the design cases considered.

As a non-structural panel covering a ‘typical’ sideguard the alternative materials provide a significant weight saving. GFRP is presently used for this purpose as it adds only 4.2kg to the ‘typical’ guard weight.

Steel is the cheapest available material for sideguard construction. Aluminium and magnesium alloys and GFRP are an alternative at up to twice the cost per component. Titanium is approximately ten times more expensive per component than steel. CFRP cost is dependent on the properties required, but is approximately less than four times more expensive per component than steel. Advances in CFRP processing technology are expected to decrease the cost of production.

Steel and aluminium offer the best recycleability option. Titanium and Magnesium can both also be recycled but at present it is more expensive and less common. Thermoset polymers, which are used in the resins of GFRP and CFRP, are very difficult to recycle due to their chemical structure. The problem is made more difficult as the fibres have to be separated from the resin matrix. Therefore, the only cost-effective recycling process currently available is to grind GFRP and CFRP and use the powder as filler.

TRL Limited ii UPR SE/084/04


Alternative designs can also be used to provide an integrated solution. By placing the trailer frame structure at the outer edges the Krone Safeliner is able to provide an integrated guard with increased lateral protection which is constructed from steel without any weight penalty.

TRL Limited 1 UPR SE/084/04


1 Introduction TRL was commissioned by the UK Department for Transport (DfT) to investigate the potential benefits of an integrated approach to the design of safety guards and spray suppression equipment for HGVs. The project aims to identify and quantify the potential benefits of an integrated spray suppression and underrun protection structure. In particular the project will aim to assess:

• Safety benefits to vulnerable road users through improved sideguards

• Safety benefits for all road users through reduced spray

• Cost and environmental benefits through improved fuel economy resulting from improved vehicle aerodynamics

As part of this work the project aims to develop a test method for quantifying whole vehicle spray that could be used as a regulatory test.

The project has been split into three modules in order to reflect the above objectives. This report has been written as part of the module of the project studying the potential benefits of improving the underrun protection through improved integration.

Improving the performance of safety guards could potentially involve increasing the stiffness of the protection and increasing the area of the vehicle that is covered by the protection. This is likely to lead to increased weight. The objectives of this report are to consider whether the use of alternative materials in the construction of safety guards could minimise the weight penalty associated with that improvement in performance.

This report reviews existing literature and data concerning the materials currently used in safety guards and uses theoretical analysis of material properties and guard designs to identify alternative materials that could be used in future designs. Issues regarding the feasibility of using alternative materials including weight, strength, cost and recycleability are considered as part of this study.

However, this report focuses on sideguards rather than on an all-around integrated solution. This is because an EC-funded 5th Framework project known as VC-COMPAT is currently being carried out in parallel with this project. VC_COMPAT includes extensive research into the performance of both front and rear underrun protection and is likely to make recommendation for changes to the regulatory requirements in those areas. Until that project is concluded and the proposed new requirements are known it is difficult to consider the weight penalties involved and which alternative materials may be suitable to minimise those weight penalties.



2 Strength requirements

2.1 Current requirements The principal requirements of the UK standard for sideguards (Road Vehicles (Construction and Use) Regulations 1986 regulation 51) are:

• 550mm maximum ground clearance

• 100mm minimum rail height

• 30mm maximum inboard of vehicle edge

• Must sustain 2kN loading on any point with not more than 30mm deflection over the rearmost 250mm of the guard and 150mm deflection over the rest

A comprehensive review of UK and EU regulations and vehicle exemptions is included in the “Review of side and underrun guard regulations and exemptions” report (Smith and Knight, 2004) also produced for this project.

2.2 Vehicle collision strength requirements The current requirements are designed to offer protection to pedestrians or cyclists, preventing them from being run over by the rear wheels should they fall against the side of the vehicle. If sideguards were required to protect against impacts from motor vehicles they would need to be much stronger.

There is no evidence of any research into impacts of cars into the side of HGVs, but the crash dynamics can be likened to rear underrun. Rear underrun protection is currently being considered by the EC project VC-Compat and has previously been the subject of international research.

Boucher (2000, 2001) conducted research on the performance of rear underrun protection using full scale testing. Different impact speeds, ground clearances and guard strengths were investigated over eleven tests. One of the guards tested was designed to deflect less than 125mm when subjected to a 350kN uniformly distributed load. It was struck using a small family car with an impact speed of 56km/h and 100% overlap. The peak force transferred to the guard was 293kN. The vehicle suffered serious damage, but there was no intrusion of the occupant compartment.

To provide protection to car occupants in perpendicular collisions with the side of an HGV, sideguards would have to be able to withstand forces of this order. The trailer frame rails may also need to be reinforced to cope with the loads that would be transferred from the sideguards as the loads will be applied transversely, inducing a twisting moment in the rails.

In a review of 1991-93 fatal accident data (Robinson and Knight, 1997) found that;

"The car to side of HGV impacts produced 70 fatalities. The vast majority of these impacted the foremost or rearmost regions of the HGV sides, for which no known and practical HGV-based countermeasures exist. Only sixteen fatalities resulted from impacts with the central section of the HGV side, and just two of those collisions involved a direction of force of less than forty-five degrees to the HGV. This does not contradict the theory that existing sideguards, designed for pedal cyclists and pedestrians, are also effective in glancing impacts with cars, though the data cannot confirm that suggestion. Strengthening the existing sideguards to withstand more substantial impacts (such as 65 km/h at an angle of 60deg) is likely to have saved roughly 5% of the fatalities."

Reviewing the HGV fatal accident database (developed by DfT project S052B/VE) for 1994-96 identified 452 car occupants that were fatally injured in collisions between cars and HGVs. Of these, 44 fatalities were from cars hitting the side of HGVs. Only 15 were from impacts into the centre of the HGV side. Thirty-three percent of the central collision fatalities had an impact direction perpendicular to the HGV, with 40% between 45deg and 75deg. The remainder occurred between



15deg and 45deg. Thirteen fatalities resulted from impacts with the front section of the side of HGVs. Twelve fatalities came from impacts with the rear section of the side of the HGV. Four of the impact locations were unknown. It is possible that a fully integrated sideguard system which extends further forward and covers the rear wheels and the section between the rear wheels and the rear of the vehicle could provide a greater level of protection in all of these impacts. A strong integrated system could also provide enhanced rear impact protection.



3 Current sideguards

3.1 S050G/VE Report Robinson (1996) conducted an extensive assessment of sideguards in a previous TRL project, a principal part of which was to survey sideguards in use. The survey was of 200 vehicles, including 51 foreign vehicles, and recorded sideguard dimensions, configuration and construction materials.

The sample of UK vehicles surveyed contained 137 vehicles with some form of sideguard, made up of 87 rigid vehicles, 45 semi-trailers and 5 drawbar trailers. The drawbar trailers were found to be very similar to semi-trailers and the small number meant they were not considered individually. Table 1

Table 1. Dimensions of UK vehicles sideguards in survey

summarises the dimensions of the sideguards measured on UK vehicles.

Rigid vehicle Semi-trailer

minimum average maximum minimum average maximum

Rail length (mm) 1340 3351 5050 2720 3616 4800

Rail height (mm) 100 111 310 100 111 220

Rail depth (mm) 15 41 70 14 45 120

Rail thickness (mm) 1 2.47 5 2 2.36 3

Distance between rails (mm)

55 203 300 150 267 310

Ground clearance (mm) 260 462 620 280 454 620

Top of guard to vehicle structure (mm)

20 263 500 0 256 560

Front of guard to front tyre (mm)

120 306 1050 - - -

Front of guard to kingpin (mm)

- - - 1750 2649 3310

Front of guard to landing legs (mm)

- - - 0 138 220

Rear of guard to rear tyre (mm)

60 233 400 80 229 320

Guard face to tyre face (mm)

-100 +31 +190 -90 +30 +120

Guard face to vehicle edge (mm)

-160 -20 0 -100 -29 0

Spacing between mounting points (mm)

140 1175 2510 70 1408 3090

Average unsupported length (mm)

- 254 - - 254 -

The foreign vehicles followed the same trends as the UK vehicles with a few exceptions:



• The minimum rail height measured was 30mm

• The average rail thickness was approximately 0.5mm greater

• The maximum distance between rails was 680mm

• The average ground clearance was 516mm and maximum 955mm

• The front of guard to front tyre maximum was 2690mm

Table 2

Table 2. Sideguard configuration

summarises the configuration details of the sideguards on the vehicles surveyed. It is clear that the UK and foreign vehicles follow the same configuration trend with guards constructed from two rails being most popular for both vehicle types. Some foreign trailers (18%) were equipped with tubular type guards, which do not conform to the regulations and were not included in the quoted figures.

UK vehicles Foreign vehicles

Rigid vehicle Semi-trailer Rigid vehicle Semi-trailer

Panel guard 0% 18% 11% 3%

Single Rail 47% 16% 33% 13%

Double Rail 53% 62% 56% 81%

Three Rail 0% 4% 0% 3%

The panel type guards were found to have a lower average ground clearance and guard to rear wheel distance than rail type guards. The gap between the top of the guard and the vehicle structure was usually zero.

The most common fitment arrangement for UK sideguards was using three mounting points, which was used on 51% of rigid and 49% of semi-trailers. Sixteen percent of rigid vehicles and 24% of the semi-trailers used only two mounting points, while the remainder used four or more.

For UK rigid vehicles, 78% of guards were constructed from steel and 22% from aluminium. Of the UK semi-trailers fitter with rail type guards, 78% were steel and 22% aluminium. The foreign vehicles (rigid and semi-trailer combined) with rail type guards were divided as 55% steel and 45% aluminium, indicating a significantly higher use of aluminium.

Eight UK semi-trailers were fitted with panel type sideguards as follows:

• Three had fibreglass panels fitted onto a conventional rail type sideguard

• Two had fibreglass panels between metal uprights but no horizontal rails

• Two had a combination of rail type guards and flat-fronted storage boxes

• One had a sideguard made up entirely of flat-fronted storage boxes

Although the load requirement in the UK regulation is 2kN, Robinson (1996) found that in reality a substantial proportion of guards were able to sustain higher loads. This was attributed to the need for guards that are able to withstand impacts during loading and unloading of the vehicle.



3.2 TCIS database The TCIS database was interrogated to gain more recent information to supplement the findings of the previous report. The database contains accidents in the UK between 1995 and 2000. 180 cases involving rigid vehicles and 161 involving semi-trailers contained sufficient data. Table 3

Table 3. Dimensional information from TCIS database

to Table 6 contain the information that was available.


minimum average maximum minimum average maximum

Rail length (mm) 1050 3214 5290 1440 3042 5000

Ground clearance (mm) 180 444 830 190 464 720

Front of guard to front tyre (mm)

40 300 1260 - - -

Front of guard to kingpin (mm)

- - - 300 2600 5850

Rear of guard to rear tyre (mm)

10 201 350 40 215 520

Table 4. Sideguard configuration from TCIS database


Panel Guard 2% 6%

Single rail 54% 6%

Double rail 43% 70%

Three rail 1% 8%

Table 5. Sideguard materials from TCIS database

Material type Rigid vehicle Semi-trailer

Steel 67% 71%

Aluminium 32% 16%

Fibreglass 1% 2%

Unknown 1% 2%



Table 6. Sideguard section type from TCIS database


Horizontal Upright Horizontal Upright

Box section 18% 11% 21% 17%

Angle section 3% 23% 1% 14%

Tubular 3% 4% 2% 6%

Channel section 73% 53% 68% 51%

Flat bar 1% 0% 2% 4%

Other 1% 7% 3% 2%

Unknown 1% 1% 4% 6%

3.3 Current materials The information from the previous sideguard research (S050G/VE) and the TCIS database indicates that steel and aluminium are the dominant material types in sideguard construction. Steel makes up more than 65% of all of the guards inspected by these studies.

Inspection of sideguards fitted to brand new vehicles at the recent Commercial Vehicle Show 2004 indicated that a significant proportion of the sideguards fitted were made from aluminium alloy, suggesting that in future there may be a greater number of this type of guard.

Inspection also indicated that the thickness of aluminium alloy and steel sections were very similar at approximately 2 to 2.5mm.

Consultation with bodybuilders and trailer manufacturers indicated that most offer both steel and aluminium alloy guards, with many also offering GRP panels. No other materials were identified as currently being used in sideguard construction for standard rigid vehicles or semi-trailers.

3.4 ‘Typical’ guard Using the information from the previous study along with the data from TCIS it is possible to derive a ‘typical’ guard. This is performed by using the average lengths for components and most popular arrangements identified.

The guard geometry is shown in Figure 1

Figure 1. ‘Typical’ sideguard

. Rails and mounts are channel section, depth 43mm, with wall thickness of 2.42mm.

260mm

235mm

3484mm

Rails & supports 111mm

254mm 254mm 1322mm 1322mm



4 Investigation of material alternatives Several possible alternative materials for sideguards have been identified. In this section the advantages and disadvantages of the materials are described.

4.1 Steel As shown in Section 3, steel is the most popular material for sideguards on vehicles in current use.

Advantages

Very cheap

Easy to manufacture; shape, weld, etc

Good strength, stiffness and toughness

Easy to recycle

Alloy can be varied to give different or enhanced properties

Disadvantages

Corrodes easily so requires painting, galvanising or other coatings

Very high density

4.2 Aluminium alloys Aluminium alloys were also popular in the surveys shown in Section 3.

Advantages

Much lower density than steel

Easy to recycle

Quite high stiffness and strength

Disadvantages

Aluminium production uses large amounts of energy

Original production quite expensive, however recycled material cheaper

Not as durable as steel

The European Aluminium Association (2004) produced literature about semi-trailers produced entirely from aluminium alloy. Using aluminium for the structure allows a significant saving of up to 1500kg over steel for the trailer chassis alone.



4.3 Advanced metals There is a vast range of possible metal alloys that could be used for sideguards, however two have been selected for consideration because they represent materials starting to become more popular in vehicle construction generally.

Titanium alloys

Titanium alloys have become more popular over recent years in sporting goods and are now making it into car production in areas such as high-end vehicle suspension components.

Advantages

High strength and stiffness, even at high temperatures

Low density

Disadvantages

High cost

Difficult to manufacture with; usually cast, although can be welded

Magnesium alloys

Magnesium alloys have been in use for cast components such as wheels for some time, but are now also being used for internal components such as cylinder heads.

Advantages

Very low density

High stiffness and strength

Disadvantages

High cost

Difficult to shape; usually cast

Magnesium is chemically very reactive

4.4 Glass Fibre Reinforced Plastic (GFRP) GFRP has become a popular mass market construction medium, initially through the aircraft industry, then motorsport and then in production cars. It remains limited either to particular components on high volume vehicles (such as bonnets or wings) or for whole body structures in specialist performance vehicles. GFRP is produced by combining glass fibres with a resin.

Advantages

Low density

Relatively high stiffness and strength to weight ratios

By constructing using a mould it is possible to produce complex 3-dimensional shapes repeatedly, allowing aerodynamic designs to be produced, see Figure 2.

Disadvantages

Difficult to shape and join once original moulded shape is produced



Susceptible to damage under impact, repairs can be complicated

Difficult to recycle.

GFRP panels offer a good option for panelled sideguards, but need to be thick to give sufficient strength to be used without a supporting substructure. The survey for S050G/VE found that GFRP panels were mounted on standard rail guards or on the vertical members of such guards. Observation of designs at the Commercial Vehicle Show 2004 showed that newer panelled sideguards can be supported by a lightweight spaceframe structure. This structure is illustrated in Figure 3, which is the same type of trailer as seen in Figure 2.

Figure 2. Aerodynamic GFRP panel sideguard

Figure 3. Spaceframe supported GFRP panels



4.5 Advanced composites Advantages

Figure 4

Figure 4. Specific properties comparison (

compares the tensile strength and modulus of conventional materials with those of carbon fibre reinforced polymers (CFRP) illustrating the benefits. Values have been divided by density to allow a direct comparison.

The size of the bands for CFRP indicate the amount of variation that can occur depending on many different manufacturing parameters, such as, fibre type, resin type, ratio of components, fibre orientation and curing method. The price tends to increase with improved properties.

www.azom.com, 2004)

Figure 4

CFRP also has the advantage that its properties can be tailored to the exact loading requirements of the structure. Therefore it is possible to provide additional strengthening in the load bearing direction, but not have any additional redundancies in other directions and thereby minimising the weight of the structure. However, such tailoring of the construction can substantially increase the complexity and cost of construction.

Like GFRP, CFRP is created on a mould which can be any shape, allowing aerodynamic structures to be produced easily.

Disadvantages

Cost is the principle disadvantage of CFRP construction. Production of the fibres is a complicated process. Moulding to a shape and tailoring properties requires a labour intensive process.

CFRP, particularly those with a high modulus, can be very brittle and therefore cannot withstand any significant impact loading. Failure of CFRP results in small shards, which could present a significant danger to other road users in the event of such shards being left on the carriageway. Failure can also result in large amount of dust and small particles which could present a significant inhalation risk to those in the immediate area. To prevent brittle failure it is necessary to introduce an aramid layer which significantly improves the fracture properties of the composite. Aramid fibres are completely synthetic and have a much higher toughness but their strength is lower, as shown in . Therefore, the hybrid product needs to be designed to give a compromised solution, which increases costs. It is common to designate carbon and

http://www.azom.com/



aramid hybrids as CFRP and this convention will be used for the rest of the report unless otherwise stated.

Repairs to CFRP can be difficult to perform while ensuring the integrity of the structure is properly maintained.

CFRP cannot be welded so must either be constructed with metal fixings included, or drilled using specialist equipment. Aramid fibres require different specialist equipment due to their specific properties.

4.6 Sandwich construction Sandwich construction involves the use of two facings usually, but not exclusively, made of one material, attached to either side of a core material. The core material is usually much weaker and less dense than the facings. The benefit of this type of construction is that there is an increase in the strength and stiffness of the structure with a lower weight penalty. Table 7

Table 7. Benefits of sandwich construction

demonstrates the benefits.

Bending Stiffness 1.0 7.0 37.0

Flexural Strength 1.0 3.5 9.2

Weight 1.0 1.03 1.06

Facings can be constructed from any material capable of being formed into a sheet, but aluminium alloys, GFRP and CFRP are the most common. The advantages and disadvantages of each material are as described in the sections above.

The two most popular core materials are honeycomb and foam. Foam is relatively cheap but honeycomb offers a more predictable behaviour when crushed because the structure is more regular. This means that honeycomb is more popular for most structural applications. Honeycombs are most often constructed from aluminium alloy or aramid fibres. Core materials are cheaper than facing materials because their properties contribute less significantly to the behaviour of the overall structure. Manufacturing costs of sandwich structures are high if CFRP facings are used.

Sandwich panels can be susceptible to damage from point impact loads. Impacts can often leave the surface undamaged but cause localised crushing of the honeycomb or failure of the adhesive interface between the two. This can result in the structure not behaving in the predicted manner under loading. In aviation applications, where this technology is common, any significant impact has to be examined using non-destructive testing (NDT) techniques such as X-ray or ultrasound, to ensure that the integrity of the panel has not been compromised. Such behaviour means that honeycomb sandwich panels are less suitable for an environment where impacts are common such as fork-lift operations in loading bays.

A research project by TNO (1996) identified the use of 1mm thick aramid facings with a PVC foam core as a good combination capable of resisting the separation of the facings from the core. They believe that this panel can resist small impacts such as those occurring during loading operations.



4.7 Recycleability of materials The European Commission is currently considering a proposal for a directive to replace the current framework Directive 70/156/EC for European type-approval. The proposal aims to extend principles of whole vehicle type-approval currently used for cars and motorcycles for the approval of other vehicle types such as goods vehicles. It is thought that the procedure could be operational in 2007. It is possible that the End of Life Directive 2000/53/EC requirements would be applied to goods vehicles at this point. The End of Life Directive sets out minimum re-use and recycling requirements for the materials used in vehicle construction. Currently the requirement for cars when the directive is enacted at the beginning of 2006 is that 80% of the vehicle by mass must be recyclable at the end of its life.

Although sideguards make up a small proportion of the weight of a rigid vehicle or semi-trailer it is worth considering the recycleability of the proposed materials to determine the impact that the use of alternative vehicles may have on meeting end of life requirements.

Table 8 presents the percentages of materials in use in products which can economically be recycled (www-materials.eng.cam.ac.uk/mpsite/materials.html).

Table 8. Percentages of materials that can currently be economically recycled

Material Recycle Percentage

Mild steel 80-90

Aluminium 80-90

Titanium 55-65

Magnesium 55-80

Most polymers 15-40

GFRP / CFRP 2.5-5

It is clear that the metals can be recycled more economically than polymer based materials. Steel and aluminium are currently recycled and reused with a high recovery rate throughout the world. Aluminium recycling is a particularly efficient process because it requires only 5% of the energy of making the primary metal. Many other materials are highly dependent on an increased demand for the recycling facilities to lead to a reduction in the recycling costs.

Recycling polymers can create notable technical difficulties. Thermoplastic polymers can be recycled quite easily by grinding them down and remelting, but thermoset polymers are very difficult to recycle due to their chemical structure. Recycling processes such as pyrolysis or hydrolysis are required and these are expensive (DeRosa et al, 2004). Technology is currently being advanced in this area and the cost of recycling thermosets is expected to decrease in future. Only thermosets are suitable for sideguards because they are much stronger than thermoplastics. Epoxy and polyester, the two most popular resins for GFRP and CFRP, are both thermosets.

Composites present an additional challenge because there are two different materials which must be separated before the recycling process can take place. GFRP is more readily recycled because it is possible, although difficult, to isolate the glass fibres from the resin more easily than with carbon fibres. At present the only form of recycling that can be performed cost-effectively with CFRP is to grind it up for use as a filler material, which is very inefficient given the properties of the base materials (Das, 2001).

The difficulties described above can be exacerbated when considering a composite sandwich structure. These structures can have different core materials, facing fibres and two different resins that all have to be separated before recycling can take place. This results in a very expensive and complicated process. Again grinding into filler is the only cost-effective option currently available.



4.8 Cost considerations The information available on the costs of composite technologies for automotive applications is very limited. Specific cost estimates for a given composite or production method cannot necessarily be generalised to all uses of that technology.

Ashby and Jones (1996) quoted the costs in Table 9

Table 9. £/kg of selected materials

based on trading prices in May 1994.

Material £/kg

Steel 0.25 - 0.35

Aluminium alloy 0.9 - 1.2

Magnesium alloy 2.2 - 3.3

Titanium 3.2 – 4.0

CFRP 3.5 – 8.0

GFRP 1.3 - 3

A comparison with current steel and aluminium prices, which are readily available, showed that these values are slightly out of date, with aluminium alloy trading at 0.84 £/kg on the 20th May 2004. However, they still provide a good relative comparison between common materials and possible alternatives, although it should be noted that these prices relate only to the materials and do not include the cost of manufacturing a finished product.

The Environment News Service (1999) gives the costs of some materials that are, or could be, used in vehicle manufacturing. Most steel used for automotive application costs well under 0.60 £/kg, while most alloys of aluminium cost more 1.20 £/kg. Extremely lightweight titanium and carbon fibre are significantly more expensive and can cost more than $8 per pound. As before, these costs are for raw materials and do not reflect the cost of the finished components.

Since lightweight metals are, by definition, less dense than steel the weight of metal required for a given component is lower. Some lightweight metals are stronger than their conventional equivalent so the volume of metal required is lower as well. Therefore, the price per component is a more useful comparison than simply looking at the price per kilo of a metal.

The Office for Technological Assessment (1995) found that the average car costs 2.70 £/kg to manufacture, of which £0.50 goes on materials. On a weight-for-weight basis GFRP, aluminium and CFRP cost roughly 3, 4 and 20 times as much as carbon steel, respectively. However, on a part-for-part basis they cost only 1.5 times, 2 times and 4 times as much as steel.

Cole and Sherman (1995) discuss the differences in production costs between materials. Cast aluminium and magnesium components are generally cheaper to produce than cast steel components but wrought aluminium and magnesium parts are usually more expensive to produce than their steel equivalents. Although magnesium costs more per kilo than aluminium, the cost for a given volume is comparable. However, machining costs for magnesium are much lower so for some components the finished component can be cheaper than its aluminium equivalent. They estimate that any weight reduction that can be achieved at a cost of less than 1.09 £/kg has a good chance of being incorporated into a vehicle.

Gaines et al (1996) discuss the benefits of using magnesium, as an alternative to either steel or aluminium. By weight, magnesium costs 5 to 6 times as much as steel and 1.7 to 2.8 times as much as aluminium. The price is also unstable. However, magnesium is 36% lighter per unit volume than aluminium and 78% lighter than iron. Therefore, on a volume and component basis the price differential is considerably reduced, with the price per unit volume of magnesium being 10% to 80%



above aluminium and from 20% below to 30% above steel. Magnesium may also have lower fabrication and joining costs. They conclude that "the total life-cycle cost of a magnesium part may actually be lower than that of one made from another material."

Das (2001) conducted an extensive review of the cost of polymer composites for the US Department of Energy. Previous research cited reported cost increases of a Body-in-White design of 62-76% and when using GFRP or CFRP instead of steel, while another reported increase of 41% to 73% for CFRP. The higher cost is primarily due to higher raw material costs and higher labour costs. The higher variable costs suggest that the materials are better suited to low-volume applications. It is found that below 55,000 units per year composite Body-in-White production is competitive with steel.

The cost of finished composite components is highly sensitive to the production methods used. Conventional production is very labour intensive as the lay-up of the materials is done by hand. Currently there is a large amount of development work being performed on the manufacturing process to decrease time and cost. One such process being developed is Programmable Power Preform Process (P4) which is a fully automated production method. Applying this could provide a 40% reduction in costs for GFRP (Chavka and Dahl 1999) and an 85% reduction for CFRP (Reinhart 1999).



5 Weight comparison

Using the ‘typical’ sideguard identified in Section 3.4 as a basis it is possible to compare the materials to determine the effect on the weight and strength performance. By consideration of a range of configuration and strength requirements it is possible to determine under what circumstances alternative materials provide substantial weight benefits.

Standard material properties have been assumed as shown in Table 10

Table 10. Material properties

, below.

Material Young’s Modulus, E

(GPa) Density (kg/m3)

Steel 200 7800

Aluminium 70 2700

Magnesium 50 1800

GFRP 30 1700

CFRP 110 1600

Titanium 115 4500

CFRP and GFRP are not isotopic materials because their behaviour is dependent on the orientation of the fibres. However, they can be constructed in a quasi-isotropic fashion by orientating several layers at different angles. For the purposes of this analysis quasi-isotropic construction has been assumed.

5.1 Current guard weights Table 11

Table 11. Weights of ‘typical’ guard constructed using alternative materials

presents the weight of the ‘typical’ sideguard when constructed from the alternative materials. This assumes that the same section geometry is used for all materials.

Material Weight (kg)

Steel 33.1

Aluminium 11.4

Magnesium 7.6

Titanium 19.1

CFRP 6.8

GFRP 7.2

5.2 Guard deformation The amount the guard will deflect under loading is calculated using simple beam bending theory. Three possible deformation mechanisms for the guard have been identified which are outlined in

. The symbols on the diagram denote the points of application of the loads perpendicular to a Figure 5



vertical plane passing along the vehicle’s longitudinal axis. The maximum allowable deflection for each case is based on the limits of UK legislation. Deflection of 150mm is allowable except over the rearmost 250mm, which is limited to 30mm.

Figure 5. Schematic of load cases

To analyse this problem the following assumptions have been made:

• Simplified failure mechanisms assumed.

• The flexural rigidity of the sections (EI) remains constant.

• Twisting moments induced in beams are ignored.

• Fixings and the trailer frame do not fail. In reality they may have to be modified.

• In cases 1 and 2 it is assumed that the vertical supports remain rigid.

The regulation 2kN load is applied at each of the load case positions on a ‘typical’ guard constructed from each of the materials. The resultant deflections are shown in Table 12.

Table 12. Deflections of guards of various materials under 2kN load

Deflection (mm)

Material LC1 LC2 LC3

Steel 6.1 4.3 7.0

Aluminium 17.3 12.2 20.1

Magnesium 24.2 17.0 28.2

Titanium 10.5 7.4 12.3

CFRP 11.0 7.7 12.8

GFRP 40.4 28.4 47.0

Horizontal member deflecting more than 150mm under loading midway between supports

Horizontal member deflecting more than 30mm under loading at end

2.

Support deflecting more than 30mm under loading at lower end

3.

1.

Maximum allowable deflection



This shows that the current guard geometry in any material except GFRP would meet the maximum deflection limits, as it exceeds 30mm under load case 3. Therefore, although the GFRP option was shown to be lightweight in Table 11 it insufficiently strong.

5.3 Different strength requirements The possibility of increasing the strength of a sideguard to resist the forces associated with collisions with cars has previously been considered but rejected on the grounds of cost and weight penalties. This section considers whether the use of alternative materials could permit lighter guards to meet the current requirements or to improve the strength of sideguards without imposing an excessive weight penalty.

The strength requirements of the guard have been modified to determine the weight of a guard constructed from the different materials under the following load conditions:

• 2kN representing the current UK regulatory requirement.

• 45kN as estimated by Robinson (1996) for a 50km/h vehicle impact at a heading 30deg to the trailer.

• 300kN from rear underrun protection work, representing a 90deg collision at 56km/h.

It is possible to identify the section sizes that would be required to avoid failure under different load magnitudes.

In Table 12 it has been identified that for every material type considered, loading of the support (load case 3) produces the greatest deflection. This case is therefore deemed to be the most critical and is the only mechanism considered for further analysis. The maximum deflection permissible is set as 30mm and the thickness of the material calculated to give this deflection.

The intent was to keep the standard channel section shape and vary the material thickness. However, under the higher loads this section was insufficient for some materials so a square box section design was considered. The box section offers a much more efficient shape for resisting higher loads, however for the GFRP this was also insufficient so a solid section was used. Box and solid sections were 111mm wide, the same width as the channel. The section selection process is illustrated in

. Figure 6

Figure 6. Section selection process

Calculate material thickness for channel section

Calculate depth of solid section required based on width of 111mm

Calculate thickness for box section with outer dimensions of 111x111mm

If thickness is greater than 43mm no longer channel section, so:

If solid section of 111x111mm insufficient:



Table 13

Table 13. Variation of section size for different materials

presents the results of the analysis. The weight calculated assumes that the entire guard is constructed from the same section as the support. If this were not the case then each of the three failure modes previously identified would need to be considered to ensure that the other sections were sufficient.

Channel Section Hollow square Section Solid rectangular

section

Material Load (kN)

Thickness (mm) Mass (kg)

Thickness (mm) Mass (kg)

Section depth (mm)

Mass (kg)

Steel 0.5 7.5

Aluminium 1.6 7.6

Magnesium 2.3 7.2

Titanium 0.9 7.6

CFRP 1.0 2.8

GFRP

2

4.0 11.9

Steel 0.5 14.7

Aluminium 1.4 14.8

Magnesium 1.9 13.9

Titanium 0.8 14.8

CFRP 0.9 5.5

GFRP

45

3.4 22.5

Steel 3.4 103.1

Aluminium 12.3 119.6

Magnesium 23.3 134.0

Titanium 6.4 109.2

CFRP 6.7 40.8

GFRP

300

126.4 217.5

Design optimisation has not been conducted to provide the most efficient section shape. Results are only intended to provide an indicative comparison of possible relative values for the different materials. Full analysis of the stresses is required to ensure that no materials reached their yield or failure point.

5.4 Different guard dimension Using the minimally compliant 2kN guard dimensions calculated in Table 13 it is possible to calculate the weight of guards of different sizes. This allows it to be determined whether alternative materials may provide a greater weight saving if there was to be future dimensional requirement legislation.

These cases are presented in Table 14. The following cases are considered:



• Guard extended to the rear of semi-trailer (guard 9m long) with additional supports at current spacing

• Ground clearance of guard reduced by 100mm

• Ground clearance reduced by 100mm and a third rail added to maintain a low rail spacing

Table 14. Effect on guard weight of configuration changes

Weight (kg)

Material Standard

Guard

Full semi trailer guard

100mm lower

100mm lower with

3rd rail

Steel 7.5 18.2 7.6 10.5

Aluminium 7.6 18.6 7.8 10.7

Magnesium 7.2 17.7 7.4 10.1

Titanium 7.6 18.5 7.7 10.6

CFRP 2.8 6.9 2.9 4.0

GFRP 11.9 29.1 12.2 16.7

5.5 Non-structural panel guards It was identified earlier that it is common to attach panels to standard sideguards to give a smooth surface that is more aerodynamic and safer for vulnerable road users. Table 15

Table 15. Weights of non-structural panels made of different materials

considered the weights of a 1mm thick panel constructed for fitting over a ‘typical’ guard. A panel to fit the full length of a semi-trailer is also presented.

Weight of panel (kg)

Material Standard

panel Full semi

trailer panel

Steel 19.5 50.3

Aluminium 6.7 17.4

Magnesium 4.5 11.6

Titanium 11.2 29.0

CFRP 4.0 10.3

GFRP 4.2 11.0



6 Integration of side and rear protection This report has focussed on the use of alternative materials to reduce, or minimise any increases in, the weight of sideguards as part of recommendations to improve the performance of sideguards. Rear guards have not been considered in detail because considerable work on rear guards is being carried out in a separate EC funded project (VC-COMPAT) and the recommendations from that work are not yet known. However, there are two issues associated with alternative materials, weight and performance that can be introduced at this stage.

6.1 Material compatibility Side and rear guards have very different strength requirements. As such, it is possible that the optimum material in terms of weight and stiffness will, therefore, be different for sideguards and rear underrun protection. If an integrated solution where the two components are physically joined is then implemented there could be issues that arise from combining of different materials.

6.1.1 Corrosion Galvanic corrosion can occur when different metals or metal alloys are coupled together. If the materials are dissimilar, that is separated on the galvanic series, there can be a flow of electric current from the cathodic material to the anodic material.

The flow of current away from the anodic material causes it to degrade, while providing increased protection to the cathodic material. If the anodic component is much smaller than the cathode the process is accelerated leading to very fast corrosion of the anode. Equally, if the cathodic component is smaller than the anode the corrosion becomes less significant.

For current to flow the surfaces must be bridged by an electrolyte (electrically conductive liquid), which rainwater and spray would provide.

The further apart on the galvanic series that the two materials are, the more readily that the corrosion will take place. A separation gap of at least 0.1V is required for the corrosion to take place.

Based on Figure 7, below, combining some aluminium alloys and steels would not cause corrosion, but some would, depending on the particular alloys used. Titanium could potentially be combined with many steels without corrosion, but coupled to aluminium alloy may be unsuitable. Given the extreme position of magnesium in the galvanic series it would be very difficult to couple with any of the other materials without corrosion occurring.



Figure 7. Galvanic Corrosion Series (www.azom.com, 2004)

CFRP and GFRP do not corrode so there would be no problems in coupling them with any of the other materials.

6.1.2 Manufacturing issues Some manufacturing problems could be encountered if different materials are used for the side and rear.

Joining different materials can present difficulties. Sideguards and rear underrun protection devices are often welded together but this may not be possible between different materials due to different melting points and behaviour when heated. For bolted connections additional design is required and titanium and magnesium alloys may need to be cast accordingly. This would be dependent on the materials to be joined, and it is believed that although the construction may be complicated none of the issues are insurmountable.

In many automotive applications in which CFRP or GFRP are currently used they are mounted onto steel or aluminium spaceframes (as shown previously in Figure 3), therefore construction using such methods are relatively standard practice.

6.2 The effect of integration on strength and weight One of the acknowledged problems with rear underrun guards is that they are often not sufficiently strong to prevent underrun in the type of collision that they were designed for. This can be particularly

Volts

http://www.azom.com/



true for low overlap collisions with guards where the ends of the rail are unsupported. The EC 5th Framework project VC-COMPAT aims to identify new strength requirements for rear underrun protection that could solve this problem. Within the present regulatory structure, the additional strength will have to be engineered into the rear underrun guard itself thus causing an increase in weight, assuming the same materials are used. However, if an integrated design of safety guard is considered where a sideguard behind the rear wheels is structurally connected to the outer ends of the rear underrun guard then the sideguard will contribute to the strength of the rear guard. In this case, the rear guard itself can be designed with slightly less strength and, therefore, slightly less weight than if it is considered as a stand alone unit without any loss of performance.

It is not possible to quantify the weight that could be saved at this time because the new proposals for the strength of rear underrun guards have not yet been developed and it is not known how strong a sideguard is likely to be in the longitudinal vehicle plane rather than the lateral plane that it is designed for. However, this is an issue that should be considered when studying the results of the VC_COMPAT programme and considering any proposals for changes to the regulations as a result of either project.

7 Alternative trailer designs In addition to the use of alternative materials in standard trailer and sideguard construction, it is also possible to use different designs as illustrated by the following examples.

7.1 Krone Safeliner Krone Trailers have produced the Safeliner, which is constructed with a truss frame structure rather than using central beams. Consequently the sides of the trailer are comprised of the load bearing structure and thus are both fully enclosed and capable of sustaining higher loading than is required for regulatory side and rear guards. The wheels are also enclosed by the structure. The manufacturers have performed tests which demonstrate that the side structure is able to deflect a vehicle approaching at a 30 degree angle and a speed of 60km/h. The car experienced serious front end damage, but the trailer was scarcely damaged. Tests have also been conducted to ensure that a pedestrian or cyclist that falls against the side of the vehicle just slides off and clear of the vehicle (Schimmelpfenning et al, 2002; Schenck, 2000). The ground clearance of the Safeliner is 270mm, considerably below the 550mm regulation height in the UK.

Despite this enhanced ground clearance and strength, the weight is approximately 7,080kg and 7,800kg for a 13.6m trailer with 3 axles in curtainside and box construction respectively. This is comparable with similar trailers constructed in the traditional manner.

Figure 8. Krone Safeliner trailer



7.2 Roadlite The Roadlite project (www.roadlite.co.uk) is a very recently completed Foresight Vehicle project to develop a trailer made from a polyester/glass mixture. The trailer uses the material in thicknesses from 2.5-10mm with additional strengtheners of hollow carbon fibre sections. At present a 9.75m trailer has been constructed to prove the concept. The trailer offers a considerable weight saving over conventional steel construction. The outcomes of the project could provide useful input about the suitability of thermoplastics in trailer construction.

7.3 Composit Trailer The Composit trailer (www.composittrailer.com) is constructed in Belgium and the US using composite materials for most parts. The trailer is shown in Figure 9, below.

Figure 9. Composit trailer

Figure 9

Several manufacturing methods are used for this trailer. Two main I-beams are constructed from protruded GFRP with a high fibre content to ensure high strength. The trailer box is constructed using sandwich panels of glass, carbon and aramid fibres in an epoxy resin, with a polyurethane foam core. This is not unusual in body building, but the facings of the panels have additional interlinking using Z-shaped pins which go through the panel which serve to stop debonding of the panel under impact. Components such as the kingpin, axles and landing gear are standard non-composite items because the weight saving would not have justified the cost of design and production in composites.

As shown in , the trailer can include side underrun protection that covers the trailer wheels. This is hinged at the top to allow easy access to the wheels and underneath the trailer.

The weight of a standard high-volume Composit trailer is 6000kg. An equivalent aluminium alloy trailer would weigh 8500kg and steel 11000kg. This is reported to correspond to a 10% reduction in transport costs in comparison with similar trailers.

Other advantages of the trailer documented by the manufacturer include:

• Corrosion resistant

• Easy to perform small repairs

• High fatigue resistance

• Good insulation

• Better grip due to the damping effects of the composites

• Greater internal capacity as the sidewalls of the box are thinner than standard

http://www.roadlite.co.uk/http://www.composittrailer.com/



The manufacturer reports that the trailer is approximately 15-20% more expensive than a comparable aluminium trailer (www.trailer-bodybuilders.com).

No reports of the in-service advantages and disadvantages of this trailer were found during this review. This means that concerns such as the resistance of sandwich panels to impacts during loading could not be considered.

http://www.trailer-bodybuilders.com/



8 Discussion This section brings together all of the information about each of the identified alternative materials. Table 16 summarises the findings.

The weight of the ‘typical’ guard using the current dimensions was calculated to be 33.1kg and 11.4kg for steel and aluminium respectively. This can be compared with the weights of guards designed to minimally comply with the UK regulation as calculated in Section 5.3. The minimally compliant guard made from steel is 7.5kg and made from aluminium is 7.6kg. This indicates that at present sideguards tend to be over-engineered and are much heavier than they are required to be in order to meet the strength requirements in the regulations.

Steel guards have many features that make them the most common type currently in use. The primary reason is production cost, with steel guards being the cheapest to produce. Steel is very strong, which is able to counteract the major drawback of its high density. Another benefit is that it is easily recycled. Where the strength benefits of steel are not utilised it is a poor choice of material. This is illustrated by its high weight as a non-structural panel fitted on top of a conventional sideguard.

Aluminium sideguards are also commonly used. A ‘typical’ guard constructed from aluminium is considerably lighter than the steel equivalent, however, the minimally compliant aluminium guard is actually slightly heavier than its steel equivalent because of its lower strength properties. The low density of aluminium makes it suitable for the non-structural panel guard cover. Aluminium alloy is slightly more expensive than steel. As with steel, aluminium is easily recycled.

The other alternative metals, magnesium and titanium alloys, have been found to provide few benefits in this application. Magnesium can offer only a very small weight saving over steel, while a titanium guard is heavier than the steel equivalent. Magnesium may be useable as a non-structural panel guard cover, however manufacturing such a panel may not be cost effective. Magnesium and titanium alloys can be readily recycled, but lack the infrastructure that is in place for steel and aluminium meaning the amount recycled at present is lower.

GFRP is found to be a very ineffective material for constructing guards from due to its very low strength requiring a large section size. However, it is ideal as a non-structural panel mounted on top of a sideguard and in the vehicle survey this was the most common material used for this purpose.

The high strength and low density of CFRP allow substantial weight savings over steel. This saving occurs over all load cases considered, from a 4.7kg saving for the minimal UK regulation guard to a 62.3kg saving for a guard designed to withstand a perpendicular car impact, when compared to the steel equivalent. CFRP also provides the lightest option for non-structural panels. Panels constructed using only carbon fibres and resin fail in a brittle manner which is unsuitable for safety guards. Therefore, it is necessary to include aramid fibres which are less strong but more ductile and prevent the brittle failure mechanism, increasing the complexity and cost of construction. CFRP can also suffer damage, such as delamination of the layers, when subjected to low energy impacts. Again, correct selection of the fibre and resin properties can prevent this. The cost of CFRP is highly dependent on the constituent materials but is up to 4 times more expensive per component than steel. Technology is currently being developed to use mass production techniques for CFRP with the intent of decreasing production costs.

Currently recycling GFRP and CFRP is not economically viable as it is difficult to separate the fibres from the resin matrix. The processes to recycle the thermoset polymer resin are also very expensive. Advances in recycling technology are required before recycling of these composites becomes economically viable.

When considering the results of this study the assumptions made in the calculations of guard strength must also be considered. By assuming constant EI material, yield or ultimate failure is not accounted for. The assumption of basic beam bending rather than more complex behaviour has also been made. For a more comprehensive analysis methods such as finite element analysis would be required.



The effect of integrating side and rear guards cannot be fully evaluated in terms of the materials used and the weight penalties or savings at this time. However, a preliminary review identified that some problems could be encountered with corrosion and joining if different materials were used for side and rear. These were not considered to be insurmountable. There could also be benefits in terms of weight if guards are integrated by allowing the sideguard structure to form part of the strength required for the rear underrun protection.

Alternative design strategies can also be used to provide an integrated solution using current materials. By placing the trailer frame structure at the outer edges the Krone Safeliner is able to provide an integrated guard with increased lateral protection which is constructed from steel without any weight penalty compared with traditional trailer designs.

Unpublished Project Report Version: Draft

Table 16. Alternative materials summary table

Weight of vehicle impact resisting guard

Material

Weight of guard based on ‘typical’ dimensions

(kg)

Weight of guard

minimally compliant

to 2kN load (kg)

Weight of minimally compliant full length semi-trailer guard (kg)

50km/h at 30deg

56km/h at 90deg

Weight of panel

covering ‘typical’

guard (kg)

Approximate cost of

materials (£/kg)

Approximate cost ratio of

typical component

Recycleability

Steel 33.1 7.5 18.2 14.7 103.1 19.5 0.30 1 Good

Aluminium alloy 11.4 7.6 18.6 14.8 119.6 6.7 1.15 1 – 2 Good

Magnesium alloy 7.6 7.2 17.7 13.9 134.0 4.5 2.75 2 Moderate

Titanium alloy 19.1 7.6 18.5 14.8 109.2 11.2 3.60 10 Moderate

GFRP 6.8 11.9 29.1 22.5 217.5 4.2 2.15 1.5 Poor

CFRP 7.2 2.8 6.9 5.5 40.8 4.0 6.25 1.7 - 4 Poor



9 Conclusions

1. Comparing a guard that is minimally compliant to the UK regulations with the ‘typical’ guard currently fitted to an HGV shows that current guards are designed to be stronger than required by regulation. This suggests that guards currently fitted are heavier than is necessary.

2. CFRP is the only alternative material identified that offers a significant weight saving over steel. Based on the material properties assumed in this report, guards constructed from CFRP were 63% lighter than the steel equivalent. The weight saving is more considerable if the strength or size requirements of the guard are increased. By using CFRP it is possible to construct a guard that can withstand a perpendicular vehicle impact at 56km/h which weighs only 23% more than the ‘typical’ steel guard currently fitted to HGVs.

3. The exact CFRP materials need to be carefully selected to give impact and durability properties as well as strength. Aramid and carbon fibres can be used in combination to prevent brittle failure or damage under low energy impacts such as during loading operations.

4. The other alternative materials considered were unable to provide a significant weight saving over steel for the design cases considered.

5. As a non-structural panel covering a ‘typical’ sideguard the alternative materials provide a significant weight saving. GFRP is presently used for this purpose as it adds only 4.2kg to the ‘typical’ guard weight.

6. Steel is the cheapest available material for sideguard construction. Aluminium and magnesium alloys and GFRP are an alternative at up to twice the cost per component. Titanium is approximately ten times more expensive per component than steel. CFRP cost is dependent on the properties required, but is approximately less than four times more expensive per component than steel. Advances in CFRP processing technology are expected to decrease the cost of production.

7. Steel and aluminium offer the best recycleability option. Titanium and Magnesium can both also be recycled but at present it is more expensive and less common. Thermoset polymers, which are used in the resins of GFRP and CFRP, are very difficult to recycle due to their chemical structure. The problem is made more difficult as the fibres have to be separated from the resin matrix. Therefore, the only cost-effective recycling process currently available is to grind GFRP and CFRP and use the powder as filler.

8. Considering integration of side and rear underrun protection could potentially offer weight benefits by utilising the strength of the sideguard to contribute to the strength of the rear guard, thus saving weight. However, where differing materials are used between the two components some problems may also be encountered due to corrosion and difficulties in joining.

9. Alternative designs can also be used to provide an integrated solution. By placing the trailer frame structure at the outer edges the Krone Safeliner is able to provide an integrated guard with increased lateral protection which is constructed from steel without any weight penalty.




References Ashby M and Jones D (1996). Engineering Materals 1: An Introduction to their Properties and Applications.

Chavka NG and Dahl JS (1999). P4 Preforming Technology Development Utilizint E-Glass and Carbon Fibres. Proceedings of SAMPE-ACE-DOE Advanced Composites Conference. September 1999, Detroit.

Cole GS & Sherman AM (1995). Lightweight Materials in Automotive Applications. Materials Characterization, 35 pp3-9.

Das S (2001). The cost of automotive polymer composites: a review and assessment of DOE’s lightweight materials composites research. US Department of Energy Report ORNL/TM-2000/283.

DeRosa RL, Telfeyan E and Mayes SJ (2004). Expanding the Use of Recycled SMC in BMC’s. Proceedings of GPEC 2004, Society of Plastics Engineers Environmental Division, February 2004, Detroit.

European Aluminium Association (2004). Moving up to aluminium: The future of road transport

Environment News Service (1999). EnvironmentNews/news/list/hemp.shtml /news/list/hemp.shtml.

Gaines L, Cuenca R, Stodolsky F and Wu S (1996). Potential automotive uses of wrought magnesium alloys. Argonne National Laboratory, USA.

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Reinhart T (1999). The Potential of Orientated, Discontinuous Carbon Fibre Preforms for Low Cost High Performance Aerospace Structures. Proceedings of SAMPE-ACEE-DOE Advanced Composites Conference. September 1999, Detroit.

Robinson B (1996). The assessment of Heavy Goods Vehicle sideguards. TRL Unpublished Project Report PR/VE/206/96 produced for S050G/VE.

Robinson B and Knight I (1997). Fatalities from accidents involving heavy goods vehicles – past trends and future solutions. TRL Unpublished project report.

Schenck P (2000). Outside Frame Avoids Side Underride, Trailer / Body Builders, 1 February 2000

Schimmelpfenning K-H (2002). Aerolight Projekt., EVPSN 2 – Workshop “Heavy Good Vehicles” May 28-29, 2002, Munich, Germany.

Smith TL and Knight I (2004). Review of side and underrun guard regulations and exemptions. TRL Unpublished report number PR SE/057/04.

TNO (1996). Design of an ultra leightweight composite semi-trailer. http://www.clc.tno.nl/projects/recent/trailer.html. Accessed on 6th May 2004.

www.azom.com (2004). Accessed on 20th May 2004.

www-materials.eng.cam.ac.uk/mpsite/materials.html. Accessed on 20th May 2004.

1 Introduction2 Strength requirements2.1 Current requirements2.2 Vehicle collision strength requirements

3 Current sideguards3.1 S050G/VE Report3.2 TCIS database3.3 Current materials3.4 ‘Typical’ guard

4 Investigation of material alternatives4.1 Steel4.2 Aluminium alloys4.3 Advanced metals4.4 Glass Fibre Reinforced Plastic (GFRP)4.5 Advanced composites4.6 Sandwich construction4.7 Recycleability of materials4.8 Cost considerations

5 Weight comparison5.1 Current guard weights5.2 Guard deformation5.3 Different strength requirements5.4 Different guard dimension5.5 Non-structural panel guards

6 Integration of side and rear protection6.1 Material compatibility6.1.1 Corrosion6.1.2 Manufacturing issues

6.2 The effect of integration on strength and weight

7 Alternative trailer designs7.1 Krone Safeliner7.2 Roadlite7.3 Composit Trailer

8 Discussion9 Conclusions

Documents

The use of alternative materials for sideguards · 2020. 11. 4. · TRL is committed to optimising energy efficiency, reducing waste and promoting recycling and re-use. In support