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Old 21st January 2021, 13:54   #1
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Different materials used in the making of our cars!

There are several materials used to make our cars which we can see, touch and feel. But some of which we do not see yet contribute significantly for the vehicle to function as intended by the manufacturer. The main materials used for making cars and their parts are steel, aluminum, magnesium, copper, plastics, composites, rubber, glass, fabric/leather and a few more. These materials have been around for quite some time but have evolved greatly and diversely. For example, we call the shell of the vehicle as BIW (body in white) and everyone would assume steel or aluminum in past, but now the naming BIW might imply the shell (as per automotive jargon) be made using Carbon fiber.

The main factors for material selection, especially for the body include thermal, chemical, or mechanical, environmental resistance, durability, ease of assembly and manufacturing. Affordability is an important consideration in vehicle design, which includes factoring in the costs associated with a car’s complete life cycle, including producing, running and scrapping costs which are mostly controlled via regulations at least in Europe. The automotive sector is constantly pushed by the governmental policies to reduce carbon emissions, improve the fuel efficiency simultaneously increasing passenger and road user safety. One solution for the manufacturer is achieve this is via material selection and optimization. There are separate departments under advanced research in every OEM, testing and suggesting new materials to be used on the cars.

Less known to the outer world, there is a significant effort that goes into maintaining a database of materials used by the manufacturer on each model and variant. This is because the ELV (End of life) requirements govern the amount of recyclability and reuse of materials used. There is a list maintained called “IMDS”, which almost all global OEMs, their suppliers use to consolidate the materials used. This list is used to verify the compliance to local and international regulations.

Let me put the materials into certain clusters for ease of explaining. It is important to understand that there are differences of materials selected in different applications and segments, so I will be referring to the cars that most of us use every day in this article.

Different materials used in the making of our cars!-1.jpg

Different materials used in the making of our cars!-4.jpg


Metals and Alloys:


This cluster of materials form the major chunk of the overall vehicle weight and raw material cost. Metals are time tested materials but have had major shift when it comes to improvement of properties thanks to the alloys (adding a combination of different materials to a base metal). To make it easy for the readers, I will start with a summary table before going to the details of each material.

Different materials used in the making of our cars!-3.jpg


Steel:
It is the most common, go-to material for body structure and outer panel design due to its strength, formability, well known process of welding and maintainability. It has a good life with proper treatment and coatings. There are different types of steel in modern car,

Sheet steel
The most used in previous generation for the most part of the body. Even here there are classifications such as cold rolled and hot rolled low carbon steel with different thickness. Typically, the thickness ranges between (0.6 to 2mm) for different parts ranging from Roof, bonnets, doors with lower thickness and load bearing structures like flanges and mounts with higher thickness.

RRST 1405: strength 270–350 MPa, relative elongation @ 36%, thickness 0.6–0.9 mm

UST 1203, 1303: strength 270–410 MPa, relative elongation @ 28–32 %, thickness 0.6-0.9 mm

ST 4: strength 280–380 MPa, relative elongation @ 38 % thickness 1.5-2.5 mm


High strength steels
With the increased focus on safety the application now requires more impact absorbing but strong enough materials to withstand vehicle dynamic stresses. This makes the HSS /UHSS options so viable since achieving similar performance using traditional materials will result in increase in weight. This is due to their property of higher tensile/yield strength. But this comes with a downside of increase in cost (up to 50% more expensive), not only because of the material but also the process involved in manufacturing (Typically HSS/UHSS requires special forming process like hydroforming).

HSS: strength between 210 MPa and 550 MPa

UHSS: strength higher than 550MPa


Different materials used in the making of our cars!-2.jpg

Stainless Steel: -
Yes, SS was used on door handles, even bumpers, exhaust tips, before the plastic parts with chrome coating took away their usage.
Currently only part which I could think off is the seatbelt buckle.

Cast Iron:
I would say this is father of all automotive materials that was used to make almost every part in older days. Its heavy, brittle and not so good for making lighter cars. Gradually got replaced with steel and aluminum, but still used in some rare cases.

Aluminum:
It is lighter (by almost 40% to steel), corrosion resistant, malleable, easily machinable and has good thermal/electrical conductivity. Also, the material can be used as load bearing when extruded. Manufacturers started using aluminum for making lightweight yet stronger shells quite recently for mainstream cars (I remember Audi explaining its space frame chassis during Iron man movie release). The problem with aluminum other than cost is the joining process, it required special welding process as it has very good electrical conductivity. Also, the NVH engineers needed to revisit blackboard as the absorption properties were completely different to that of steel.

Used in sheet and cast form for other applications than the BIW are,

Cast - suspension components, engine & transmission parts, alternator casings, flanges, starter motor housing, heat sinks for electronics and a lot more.
Sheet – Heat exchangers (radiators), door panels and bonnets (specially for pedestrian safety).

In some rare cases, few OEMs are trying to use them to replace copper wiring on non-critical components due to cost reasons – copper cladded aluminum wires. There are many more aluminum alloys with even more applications which are not mentioned here.

Copper:
I would say the least looked upon material in automotive industry, but the most important material when it comes to electrification. So, I am increasing the scope of my article for copper and added certain interesting trends and details.

Before we start, did you know?
1. The body of the 1921 Rolls Royce Silver Ghost is completely copper.
2. The Tesla Roadster is also the first commercially available automobile powered by an electric motor powered by a copper rotor.
3. In 1948, the average family car contained only about 55 wires amounting to an average total length of 150 feet. Today's luxury cars, on average, contain some 2000 copper wires adding to few kilometers in length.
4. Exxon added copper in their lubricants to make engines run smoother and last longer.
5. There are copper-carbon bushes and for dry lubrication applications.


Different materials used in the making of our cars!-cu1.png

Copper is in my view a superman of the material world; over the years its properties have made copper to have a vital role in many of the applications. Some of the properties include, thermal and electrical conductivity, corrosion resistance, malleable, lubricative, solderability, creep resistance. There are many alloys of copper that is used in auto industry especially brass.

Mostly copper is seen as just an electrical application material where the main component is wiring harness and connectors. Typically, in 2020 an ICE vehicle uses anywhere between 3 Kgs to 6 Kgs of copper for wiring harness and adding more features means more wires and more copper. But the use of copper can be optimized be selecting different grades. Electrolytic-tough pitch is the most common type used in wiring. Oxygen free copper is also used in special applications to reduce the resistance. Apart from wiring, it is also used in PCBs (Printed circuit boards) and electronics, components like alternators and motors, brake lines (Copper-nickel), alloys in gearbox components as coatings, new generation of radiators replacing aluminum.

Different materials used in the making of our cars!-harn.jpg

With the increase in EV penetration the copper content used in vehicles will only be going up and more research will be on making more cost effective and less resistance copper alloys.

Magnesium:
It is the lightest of all the metals that are currently used in automotive industry with density of just 1.74 g/cm3, which translates to being 30% lighter than aluminum and 75% than the steel. There are some complications in using magnesium and special design considerations are required due to its drawbacks compared to aluminum when it comes to fatigue, ultimate tensile strength but structural properties generally are comparable. It is used mainly on steering wheel core, instrument panel structure, wheel rims and transfer case.

Lead:
Major chunk goes to battery and in older vehicles solders on PCBs and electronics. It is one of the six most hazardous materials on which restrictions are imposed. Slowly this material will be phased out due to advancement of the LI and other chemistry batteries and also the lead free solder(already in use).

Gold:
Yes, there is gold in your car and it is not the same as you think where rose gold or white gold panels are used on ostentatious cars. There are plating requirements for the connector terminals and relays of safety critical ECUs and also some elements on PCBs where processors are assembled.

Please stick on to this thread for sometime and check on the weekends for update on other materials(Plastics - a vast subject).Also, feel free to add your posts explaining somethings that I have missed.

Source and Credits: Various research papers, Google images and official websites of AIS, Copper.Org, Copperalliance.

Last edited by saikarthik : 26th January 2021 at 19:30.
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Old 26th January 2021, 16:13   #2
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re: Different materials used in the making of our cars!

Rubber


In 1839, Charles Goodyear vulcanized rubber, and patented it thereby modifying the mechanical properties of natural rubber which had its limited use expanded to new horizons.

Rubber in general classification reminds us as flexible, energy absorbing, cushioning material. There are literally dozens of types with specialized properties for every demanding application but, there are few common properties which are

• Electrical insulation
• Chemical and grease resistance
• Excellent resistance to petroleum and oil
• Hot and cold temperature sustainability
• High tear strength and elasticity
• Ozone resistance

Some important specifications to consider while selecting any rubber material for any application are: Density, hardness, elongation @ break, compression set, temperature range and tensile strength


They are generally classified based on material type: Natural Rubber (NR) and the synthetics Ethylene Propylene Diene Monomer (EPDM), ,Styrene-butadiene Rubber (SBR), Nitrile (NBR), Silicone, Fluoroelastomer (FKM), Butyl (IIR).

Applications generally include:
1. Tires, mud flaps, dust covers, mats
2. Vibration arresting & Dampening - bushes and mounts
3. Sealing - O rings, grommets, plugs, beading, gaskets
4. Padding and anti-slip - Pedal pads,
5. Insulation - electrical isolation and temperature seals
6. Routing - ducts and hoses,
7. Covers - battery terminal cover, rubber boots on electrical connectors and spark plugs
8. Consumables - A lot of sealants include molten rubber
9. Other - Valves, trays, heat shrinks, bellows, belts etc...

Some of the process involved in making them are compression mounding, extrusion, dipping.


Different materials used in the making of our cars!-rub-1.jpg

Special focus is given to the rubber materials used for NVH design and you would have noticed few patches stuck on the panels or holes for no reason and sealant over use like an aftermarket job. The former is called butyl patches and they arrest the noise from seeping into the car. They are often found with a layer of aluminum foil in the places where there is heat.

Different materials used in the making of our cars!-interior-car-nvhbottomb.jpg

Last edited by saikarthik : 26th January 2021 at 18:02.
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Old 26th January 2021, 17:18   #3
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re: Different materials used in the making of our cars!

Glass


Automotive glass is very different from the ones which we use in our buildings. The application demands the glass to withstand constant vibration, flex of the body, varying temperatures (gradual and shock), impact on collision. So, a specialized solution is needed integrating all aspects according to the requirement.

There are different types of glass dictated mainly by the component placement and usage. But mostly 2 types used are laminated and tempered.

Different materials used in the making of our cars!-g1.jpg

Tempered Glass:
This type of glass will shatter on the impact, but the process of tempering ensures that the glass shards are blunt enough not to pierce any occupants or people around. Mostly used on side windows, quarter panels rear windshield and in some cases sunroofs. You can see the marking labelled as tempered on the glass panes and is 4 times stronger than a regular annealed glass.

Laminated Glass:
This is same as tempered glass but a polyvinyl butyral (PVB) sheet is sandwiched between two glass panes and moulded to single unit. This is required on front windshield because in the event of crash the laminate holds most of the glass shards without flying around and injuring the occupants and mainly blinding people sitting in the front.

Other types include,

Acoustic (Control) Glass:
Cabin noise is a measure of premium-ness to any vehicle. This glass can filter out road, traffic and engine noise up to 40% based on the quality.

Tinted Glass:
The glass reduces the solar load on the passengers by filtering out UV rays, special IR reducing filters are also used in some cases. But currently dictated by transparency % regulation the tint is very mild. It is good to note that not all tinted glass are excellent in filtering UV rays, it depends on the filter.

Embedded Glass:
As the name suggests the glass has embedded elements - usually an antenna or defogger element.

Let us not forget bullet proof glass on armoured versions of Merc S-Class or BMW high security vehicles

It is very complex engineering and not to be taken lightly. There are even some very specific requirements on windshield glass for HUD application.

Last edited by saikarthik : 26th January 2021 at 18:01.
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Old 27th January 2021, 07:47   #4
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Re: Different materials used in the making of our cars!

Thread moved from the Assembly Line to Tech Stuff. Thanks for sharing!

A related discussion (How cars are made from Materials)
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Old 28th January 2021, 11:38   #5
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Re: Different materials used in the making of our cars!

That was a lot of intresting information, learnt a lot from it. It was amazing to see the change in percentage of materials throughout the years. Let's see what the future brings in
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Old 28th January 2021, 14:26   #6
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Re: Different materials used in the making of our cars!

Nice data there Karthik. Rated it. If you can add some more detail on the High Strength steel that these new age cars boast of and the reliability in the detail will be more helpful.
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Old 28th January 2021, 16:48   #7
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Re: Different materials used in the making of our cars!

Thanks for this great write up, much appreciated.

A few more nerdy / anorak additions:

Quote:
In 1948, the average family car contained only about 55 wires amounting to an average total length of 150 feet. Today's luxury cars, on average, contain some 2000 copper wires adding to few kilometers in length.
What is also worthwhile to mention is that not only has the length of wiring increased considerable, the insulation of wiring looms has come a long way too!

The other thing is that of course, next just supply power and analoge electrical signals, these days just about all modern cars also have digital signal running between the various computers/controllers, switches and sensors. All over a so called CAN bus. Requiring a different kind of wiring from analogue signals.

Copper is a very versatile material as you mention;

Quote:
brake lines (Copper-nickel)
Whereas Copper is an element (and thus found in nature) the copper-nickel you are referring too is known as Brass. It is man made, an alloy.

Actually, normal brass is not used for brake lines. It would be to soft.
Even if it looks like brass, it will be a special kind of brass that has higher nickel content, but also a substantial amount of steel in it. Regular Brass is not suitable for brake lines.

These days you will find more and more steel brake lines. Regular steel or galvanised steel, or even better stainless steel brake lines.

And you will still find braided brake hoses in many brake systems as well. (When a flexible connection is needed, e.g. at the calipers on the front wheels)

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Old 28th January 2021, 19:32   #8
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Re: Different materials used in the making of our cars!

People maybe surprised to know that a lot of Sintered (also called as powder metallurgy ) component parts are used in Engine, Transmission and Suspension of modern car. Sintered parts are made from iron powder (along with exotic metals like molybdenum, Manganese etc.,) compressed at high pressures using hydraulic & mechanical CNC presses and heat treated in continuous furnaces. These parts have necessary strength, wear resistance etc to meet the demands of design. India is a major manufacturer of Sintered steel parts.

Parts produced by powder metallurgy are Synchroniser hubs, VVT Sprockets, Pulleys, shocker pistons, valves , valve seats, valve guides and the list is huge.
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Old 29th January 2021, 08:55   #9
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Re: Different materials used in the making of our cars!

Quote:
Originally Posted by saisree View Post
If you can add some more detail on the High Strength steel that these new age cars boast of and the reliability in the detail will be more helpful.
Thank you. I was thinking of adding more to it specially with all the crash related topics are in hot seat in the forum. I am no expert but will try to add during weekend if possible.


Quote:
Originally Posted by Jeroen View Post
What is also worthwhile to mention is that not only has the length of wiring increased considerable, the insulation of wiring looms has come a long way too!
The other thing is that of course, next just supply power and analoge electrical signals, these days just about all modern cars also have digital signal running between the various computers/controllers, switches and sensors. All over a so called CAN bus. Requiring a different kind of wiring from analogue signals.

These days you will find more and more steel brake lines. Regular steel or galvanised steel, or even better stainless steel brake lines. And you will still find braided brake hoses in many brake systems as well. (When a flexible connection is needed, e.g. at the calipers on the front wheels).

Jeroen
Thank you for your add-on Jeroen.
Wiring harness has become more complex as you mentioned due to more number of signal wires, sensors, ECUs and even HV cable routing during design. A typical luxury car will have at least 3 to 4 CAN and a couple of LIN channels. With ADAS we even see ethernet connections coming into harness and a lot of design standards are being newly introduced. Harness design is now thought
about during architecture design itself due to all this complexity. I can write a thread or a additional post on harness design if people are interested.

And, thanks for the info on brake hoses. I see some are even encapsulated or coated with rubberized material to prevent damage and color coded near the ABS/ESP unit for easy diagnostics.

Quote:
Originally Posted by Allterrain View Post
Sintered parts are made from iron powder (along with exotic metals like molybdenum, Manganese etc.,) compressed at high pressures using hydraulic & mechanical CNC presses and heat treated in continuous furnaces. These parts have necessary strength, wear resistance etc to meet the demands of design. India is a major manufacturer of Sintered steel parts.
Yes, there are many processes that I have not mentioned. Sintering was very curious for me initially, I learnt and saw the process of manufacturing tungsten filaments sintering and welding onto molybdenum lead wires for automotive bulbs in Osram factory (Foshan, China) and was flabbergasted by its complexity. The filament is so delicate that they wrap its ends in a thin sheet of molybdenum and use programmed welders with real time load sensing and adjustment.

Last edited by saikarthik : 29th January 2021 at 09:06.
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