Materials in vehicle construction: Consider repair cases!


Whether steel, aluminium or GRP as the base material: When selecting materials in vehicle construction, also consider damage cases in production and their repairs.


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Repair cases for vehicle parts

Damage to truck with dented sheet metal for repair in vehicle construction | insights by LAMILUX

It is well known that it is important to consider the entire life cycle of components or systems when assessing the quality and functionality of a material. Commercial and transport vehicles in particular are inevitably damaged within their individual life cycles during their periods of use.

Accordingly, they have to be repaired or replaced - for example as a result of accidental damage, overloads or regular wear and tear. The better a material is adapted to these load situations initially, the more likely it is that damage can be avoided - although not completely. Therefore, the behaviour of the vehicle materials in case of repair is essential for their choice.

But construction materials can also be damaged during vehicle production itself, for example through improper handling or incorrect storage. This results in waste, which can sometimes be very expensive. But do damaged components have to be discarded immediately or is there a repair option that preserves all functions, the appearance and the durability of the material? In the best case, yes, but not for every material in the same way. In addition, the question arises whether the cost of a repair is proportionate to the resumption of the material in the production process - or whether discarding it as a permanent cost factor is actually cheaper.

When deciding pro or contra material, it is therefore necessary to consider how it will behave in the case of repairs to vehicle parts or maintenance measures. And not only the possible costs, but also the effort and complexity estimated for the use of certain materials for repair cases play a role.

Metals: High susceptibility to external deterioration

The basic decision as to which construction material is used in vehicle construction, for example in the side walls, roof construction or as floor material, is made between metals, wood or plastics. Let's take a closer look at metals in this section. Due to the increasing demand for lightweight construction, aluminium is high on the list of metals. However, steel also continues to be a tried and tested material, as it offers great stability above all.

The disadvantages of steel and aluminium are as follows: Both materials are susceptible to any kind of external impairment. These can occur relatively quickly, especially in the manufacturing process, due to pressure or impact effects. Such hazards already begin during storage or transport of the semi-finished products. Even the impact of other parts or tools or other mechanical impairments can easily lead to dents or bumps in the metals. The effort for smoothing the aluminium or steel bodies is enormous and causes correspondingly high costs. 

Repairing holes and dents in metal in vehicle construction | insights by LAMILUX

In the case of stronger impact or shock effects in the direction of the metals, not only such deformations but also real holes can occur. These not only impair the surface visually, but are also difficult or impossible to repair. Depending on the position and extent of the damage, more or less material has to be removed. If the damage can be repaired with reasonable effort and expense, it may have to be repainted afterwards.

Caution is advised when grinding steel or aluminium, when denting the sheet metal or when using so-called hot straightening. Particular caution is required when using aluminium because the yield strength of aluminium is very low, lower than that of steel.

Accordingly, fractures or cracks in the material can occur more quickly. Special tools are therefore always needed to repair these metals.

The same applies to vehicle bodies made of a multi-material mix. Since, as the name suggests, different materials and joining processes are used here, the repair of the parts is correspondingly more demanding. For example, instead of welding, mainly bonding and riveting methods are used here.  

We have summarized further advantages and disadvantages of steel and aluminium and their comparison with glass-fibre reinforced plastics in a separate article.

Fibre-reinforced plastic: Enormous load-bearing capacity with light weight

Carbon or glass-fibre reinforced plastics (CRP or GRP) are used in vehicle construction primarily for lightweight reasons. But although their weight is so low, their bond is very strong: glass and polyester resin defy external influences such as impacts and the weather. Even the use of road salt leaves GRP cold; it does not corrode or rust.

GRP components are also hard to impress when it comes to mechanical resilience. They withstand punctual impacts or blows, such as the impact of hailstones on the outer skin. Unlike aluminium, for example, this does not leave any marks on GRP.

If damage occurs due to improper handling or accidents, it can usually be repaired quickly and with little effort. For example, in the case of purely visual damage to the outer skin, the affected areas can be filled with an ordinary putty knife and special repair compounds. If the damage extends deeper into the structure, glass fibres can be re-laminated. The affected areas are then sanded in a simple manner for repainting.

Lightweight construction and repair with GRP plastic sheets in vehicle construction | insights by LAMILUX

GRP saves material, process, repair and disposal costs

GRP production on flat web line for material for vehicle construction | insights by LAMILUX

However, the uncomplicated processing of components made of GRP materials is not only evident in the case of repairs to the finished vehicle. Even in the conventional manufacturing process, the handling of composite materials is easier and often quicker than with metals. On the other hand, metals have another advantage:

Accumulated steel and aluminium scraps are usually collected for a fee, whereas GRP scrap has to be disposed of. This applies in particular to production scrap, i.e. edge pieces or parts that are discarded as waste after cutting or as recesses.

But since GRP as a base material can be produced easily, quickly and with a precise fit, the GRP manufacturer can produce individual custom-made products for the components in vehicle construction. What is subsequently omitted in terms of cutting or edge pieces is minimized. The GRP producer LAMILUX can manufacture customized plastic sheets or plastic rolls up to a width of 3.20 metres and in any length. Another factor in the choice of material: Sharp edges, as they inevitably occur when cutting or shearing metal parts, do not occur when cutting GRP sheets.

A conclusion: Thinking holistically about material selection in vehicle construction

When selecting materials for vehicle construction: Consider repair cases! Manufacturers can save material, process and disposal costs by selecting the right material for their application. A precise and holistic consideration - including the repair case in production - is therefore always worthwhile. After all, the properties of each material qualify it for a specific application. We have prepared a series of articles on the respective advantages and disadvantages of steel, aluminium, wood and GRP to help you choose the right material.

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