It’s pretty surprising, but a lot of people don’t know what their car is made of. Looking at it, it’s hard to tell. When you touch your door, it probably feels pretty smooth and plastic-like. Are car doors made out of plastic, or what? In this short guide, I’ll answer this question and teach you everything you need to know.
No, almost every car door is not made out of plastic. It will use either aluminum or steel with a layer of paint over it and a topcoat. That’s why it feels plastic-y when you run your finger across your car door. In fact, your car door is made out of the same material that the rest of your car’s body is made of.
The Parts of a Car Door
Before diving into specific material selections, I should describe the parts of a car door. This will probably answer your question inadvertently.
Door’s Outer Skin
The skin is the part of the door you’re probably asking about. This piece matches the color and material of the rest of the vehicle. The skin is attached to the framework of the car.
The handles are the parts that you grab. When you pull them, a mechanism inside of your car door will move around and allow the door to open (if your door doesn’t open, follow my guide for it here).
The exterior handles are typically made of hard plastic. On old vintage cars, it’s not uncommon to see chrome metal handles.
Of course, there is also a window in most car doors. These are made of glass that goes through some additional engineering to make them shatter-resistant and much safer.
Around the window is a piece of trim. This is typically plastic or rubber. The trim will keep the window in place, and it’s a culprit when you have a window that keeps sliding down.
Material: Plastic or rubber
The metal hinges are on the innermost corner of the door. Just like door hinges in your home, these will help your door open and close comfortably. If you ever have an accident and your car door won’t close, take a look at your hinges for troubleshooting.
The only job of the weatherstripping is to keep outside weather away from the interior of your car. It’s made of rubber and it seals the gap between your car door and the rest of your vehicle. Most notably, it prevents rain from seeping in during a storm.
The panel is the piece that hides all the internal components of your door. It comes off as a single piece, and it’s largely made of plastic or leather with minor metal accents.
Once removed, you can fully access the interior of your car door and the framework.
The panel of your door is the metal exoskeleton. It makes up the structure of each door, and it’s going to protect you during an accident through designed crumple zones.
Once the door panel is removed, you’ll mostly see the door frame metal. The rest is simple linkages used to roll your windows up and down or open your door via the handle.
The switches on your interior door armrest will control some of the electronics around you. It will roll up and down the windows in the car, lock and unlock your doors, and perhaps even move your side mirrors around automatically.
These switches are almost always made out of plastic.
You might also have a layer of insulation inside of your door. It’s typically affixed to your door panel, so once your panel is removed the insulation comes with it.
Material: Insulation foam
Just like any other insulation, this is here to keep the cabin of your car more temperate and ignore exterior temperatures.
Most doors made today will have some sort of plastic sealant that’s visible once the interior car door trim panel is removed.
Material: Plastic tarp with an adhesive sealant
Its purpose is to primarily keep water from getting on the electrical wiring tucked away behind the car’s door frame.
Finally, you have the speakers. These are located in your door with a plastic covering over them. Most of the time, the covering is part of the door panel. If you upgraded your car’s stereo system, you already know all about that. If not, then follow my ultimate guide to buying car speakers.
What Is the Car Door’s Outer Skin Made of?
You’ll notice that I didn’t mention what material the outer skin or exterior handle is made out of. That’s because I wanted to discuss it in this section instead.
Both of these pieces are almost always the same material as the rest of the car’s body. In general, a car door will be made out of aluminum or steel. Some fancier cars use magnesium or carbon fiber (which is technically not plastic, contrary to popular belief).
Are Car Doors Made of Plastic?
As you saw in a previous section, car doors aren’t entirely made out of plastic. Really, the only plastic pieces are the interior panel and the trim around the window.
If you’re wondering if the exterior part of the door you see is made out of plastic, the answer is almost always “no”. It’s made of metal, and there’s a good chance that metal is steel.
In the old days, a couple of cars used fiberglass bodies. This is an engineered plastic that looks almost like woven wool if you look at it closely.
The Exceptions to the Rule
There are a handful of modern cars that still use fiberglass as an homage to their roots. Off the top of my head, I know that Corvette and Lotus still use fiberglass in some of their cars.
There are another dozen or so cars that used fiberglass in their cars from the 1960s until the early 2000s. Most of them were European brands and there were a few outliers, but they all swapped to more manageable materials after. It turned out to be a pretty poor design decision.
Why Not Make Plastic Doors?
With 3D printing becoming more popular, why don’t car manufacturers use plastic doors? Even without 3D printing, you can injection mold a ton of doors for way cheaper than it would cost to make metal ones.
Well, before you file that patent let me tell you some reasons why auto manufacturers don’t make plastic doors.
One thing about plastics is that they expand and contract way more than metals do. In other words, their thermal expansion is more sensitive and severe.
If you look at an old Saturn that used plastic doors, you’ll see a pretty big gap around the exterior of the door. Why? To accommodate for the door getting bigger when it’s hot out. Without this designed gap, the door would hit the body and cracks would form along the intersection until something snapped.
Not as Safe
Crumple zones are a huge part of car designs today. In the safest car brands like Volvo and Subaru, they go the extra mile to make the car crumple around you so that the driver stays safe during an accident.
There are laws that say these zones need to exist in the first place in order for a car to be driven on American roads.
With plastic, this is almost impossible to do. Plastic is exponentially weaker than steel. That means that in an accident, it’s more likely to bend and break, which would fail the safety test.
One aesthetic flaw with plastic is that it gets discolored too easily. If you have a plastic desk that you’ve used for a while, you will probably notice that it’s wearing in locations that you touch a lot (like where the mouse moves).
Even worse, it’s hard to revert this discoloration on plastic. It’s hard enough to prevent your paint from fading, but it’s another thing altogether trying to keep plastic pristine looking.
Really Hard to Form
Forming plastic is much harder than working with metal. With metal, you can make a car door using a mold or stamp, and it takes very little time. With fiberglass, the car needs to be nearly hand-made and formed.
Since this process takes much longer and requires manpower, it drives the price up. While plastic starts out being an inexpensive choice as compared to metal, the prices will become similar after this work is factored in.
Paint Finish Is Low-Quality
Another aesthetic problem with plastic is that the paint doesn’t look great on it. A painted plastic piece will suffer a lower quality finish when it’s compared to a painted steel part.
A lot of this has to do with the surface finish of metal and plastic. Plastics have a hard time keeping a smooth surface. This isn’t ideal for the painting process. Paint likes a flat, smooth area to stick to in order to get the best results.
Are All Doors the Same?
All four doors in your car are going to be nearly the same. There are a few key differences like the internal wiring, where the hinges are located, and the form that the exterior follows (to keep your car’s lines looking nice).
Besides that, the material of composition is identical. They all have nearly the same parts, with the speakers and switches being the only differences.
More specifically, all four of your doors will be made of the same material. Unless you drive one of the rare exceptions, that material is not going to be plastic.
Why Not Use Stainless Steel?
A big reason why your car has paint and a topcoat are because steel and even aluminum are not corrosion-proof. Over time, rust will inevitably form on both of these materials.
If you know about materials, you’ll know that stainless steel doesn’t rust as easily. If you use stainless steel, you won’t have to paint the car and you can save money there.
Well, price is the issue. Stainless steel is significantly more expensive than standard (carbon) steel. It’s still a wonder that John DeLorean made a full car out of stainless at such a great price. Just know that it’s cheaper to use regular steel or aluminum and just paint over it.
I wonder how many people were shocked to learn that their car door isn’t made out of plastic. If you want more articles that might surprise you, check out the rest of my blog. In addition, I have a list of car products that I think you’ll love.