Plastic Body panels?

[boxedin]

As my car is in a body shop having various parts replaced, so I'm mulling over various 'whys' at the moment.

I'm wondering why only the bumpers are made of plastic and not the rest of the car?

Does anyone know?

[MysteryLemon]

Lots of modern cars have plastic body panels these days.

Wings are quite often plastic. Aren't most of the Smart Car panels plastic? The Mercedes A-class has a lot of plastic, as does our renault scenic.

Less stuff to rust in Mercedes case.

[MarshPhantom]

The Citroen BX used a lot of plastic, the bonnet and rear hatch were as well as other stuff.

[Superhoop]

Lots of French stuff has plastic front wings, and pre 2010 Mazda5's have a completely plastic tailgate..

On the 'not so visible' scale, Peugeot, Mazda and a few others have plastic front panels, which house the radiator, lamp holders etc

[smiffy555]

The McLaren 12c has SMC doors, rear body qtr panels, air brake & engine cover I believe

Range Rover Evoque has an SMC tailgate

Bentley GTC also has SMC deck lid......

[mids]

MysteryLemon said:

Lots of modern cars have plastic body panels these days.

Yip, all body panels in the i3 are thermoplastic (apart from the roof)

http://youtu.be/bsSzHNI3dQo

[davepoth]

Plastic panels (as opposed to carbon composite ones) don't add much structural strength, unlike steel panels. Cars with plastic panels (the Smart is a good example) generally have their strength in a chassis or safety cell that the panels are bolted to.

[dxg]

The Fiat Tipo (remember those?) had a plastic tailgate, supposedly to keep weight down, but in reality because they couldn't press the steel into the shape of the wrap-around c-pillar.

Or so I was told...

[dxg]

mids said:

MysteryLemon said:

Lots of modern cars have plastic body panels these days.

Yip, all body panels in the i3 are thermoplastic (apart from the roof)

http://youtu.be/bsSzHNI3dQo

Interesting that they're pushing the sustainability angle in that vid. Wasn't that the angle they took with the plastic body of the Z1 (which was an awesome car for all kinds of reasons...)

[MysteryLemon]

dxg said:

The Fiat Tipo (remember those?) had a plastic tailgate, supposedly to keep weight down, but in reality because they couldn't press the steel into the shape of the wrap-around c-pillar.

Or so I was told...

I had a Tipo once upon a time. The tailgates were indeed plastic of some sort, as were the pieces above the rear side windows.

Not sure which part of the tailgate you refer to that they wouldn't have been able to press. I suppose the sides to the tailgate are very slab sided but wouldnt have thought it would be an issue? The overall shape is pretty much an enlarged Fiat Uno tailgate, and they were all metal.

[HaloGen8]

Citroen BX tailgate was the earliest I recall.

My old Clio (02 plate) had very flexible plastic front wings.

[marshalla]

[kambites]

marshalla said:

Yes, in hindsight the GRP chassis wasn't a very good idea.

[GroundEffect]

davepoth said:

Plastic panels (as opposed to carbon composite ones) don't add much structural strength, unlike steel panels. Cars with plastic panels (the Smart is a good example) generally have their strength in a chassis or safety cell that the panels are bolted to.

Yup. Doors for instance have most of their strength in the skin therefore need to be steel. That is the general case.

[kambites]

GroundEffect said:

Yup. Doors for instance have most of their strength in the skin therefore need to be steel. That is the general case.

Surely these days most of the strength of the doors is in the bloody great RSJ they run through the middle of them for side-impact protection?

[boxedin]

Interesting. I'd have thought pop-on panels, pre-painted would have been a standard item by now.

They'd clean up in the Spanish market; IME trying a find a car in Spain without any bodywork damage is nigh-on impossible.

[Ultuous]

MysteryLemon said:

dxg said:

The Fiat Tipo (remember those?) had a plastic tailgate, supposedly to keep weight down, but in reality because they couldn't press the steel into the shape of the wrap-around c-pillar.

Or so I was told...

I had a Tipo once upon a time. The tailgates were indeed plastic of some sort, as were the pieces above the rear side windows.

Not sure which part of the tailgate you refer to that they wouldn't have been able to press. I suppose the sides to the tailgate are very slab sided but wouldnt have thought it would be an issue? The overall shape is pretty much an enlarged Fiat Uno tailgate, and they were all metal.

It looks like there's a fair amount of material that needs to be drawn down in the cast of the Tipo - it probably is 'pressable' (particularly with modern/ advanced press tools) but it wouldn't surprise me if the design favoured plastic in the interests of both costs and quality/ repeatability.

(... and given the quality of steel Fiat seemed able to obtain at the time/ lessons learned from the Uno! )

[MysteryLemon]

boxedin said:

Interesting. I'd have thought pop-on panels, pre-painted would have been a standard item by now.

They'd clean up in the Spanish market; IME trying a find a car in Spain without any bodywork damage is nigh-on impossible.

This.

I'm surprised there isn't a car out there where every external panel is replaceable with a few bolts. Why do cars still have rear quarters and sills that are part of the chassis? A design where everything structural is internal and covered by a plastic, painted panel, readily available off the shelf from a dealers, would be awesome. Change the colour of your car by just popping off the exterior panels. Big scratch? Just buy a new panel.

[hedges88]

Though they were not sold here Saturn, which was the USA's Vauxhall, had all plastic body panels on a lot of their earlier models

Edit: Just to add, the B Pillars are really weak so a lot of cars like this have the seatbelt mounted to the door!

Edited by hedges88 on Saturday 5th October 11:15

[alangla]

HaloGen8 said:

Citroen BX tailgate was the earliest I recall.

And the ZX after it. Front of the ZX ahead of the slam panel was also pretty much all plastic. When I had my shunt with the deer I had to replace the bumper, radiator grille (outer, attached to bonnet & inner, attached to slam panel), wing liners & air guides for the radiator, all plastic, all wrecked by the impact!

My cousin was working as a service manager for a large Citroen dealer when the ZX came out, I remember him saying the main reason the ZX had a metal bonnet (with a large sound deadening mat inside) was that the plastic ones couldn't deaden the engine noise sufficiently (bear in mind the favourite engine for that car was the XUD 1.9 diesel, both NA & Turbo)