Fiberglass is a prominent material for building boats. It's well-tested and durable. Over the years, there have been few attempts to adopt fiberglass as in automotive industry:

Overall, while fiberglass body is used in the industry, it isn't widely adopted. Why? What are the pros and cons and why cons outweight pros?

  • 5
    All Corvettes ('53 C1 to current C7) have glass or carbon fiber bodies. Commented Feb 18, 2016 at 14:39
  • @MooseLucifer good point, i'll edit the question to reflect that.
    – Koder
    Commented Feb 18, 2016 at 19:51
  • 1
    The Lotus Europa was also an all fiberglass body. Most of the steel was in the double "Y" frame and the bumpers.
    – cdunn
    Commented Feb 18, 2016 at 21:45
  • what about Henry Ford?
    – zoplonix
    Commented Feb 18, 2016 at 23:42
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    @cdunn - many Lotus cars used GRP bodywork with a steel chassis. Elan, Elan +2, Europa, Esprit, Elite (the 1970s one), Eclat and Excel. The original Elite used a GRP monocoque with no separate chassis but it was expensive to produce and they switched to the steel backbone chassis with the cheaper Elan.
    – Kickstart
    Commented Feb 19, 2016 at 9:16

4 Answers 4


I think the main disadvantage of Fibreglass (aka Glass Reinforced Plastic or GRP) is that it cracks and breaks in an impact, rather than deforming and absorbing energy like metal does - so a GRP bodied car would still need an internal crash structure to protect the occupants, removing a lot of the advantages.

British Reliant cars (particularly the Scimitar) in the 1970s had GRP bodywork, and many have been scrapped due to rust in the internal roll-over bars - which are bonded into the bodyshell and to very difficult to repair!

Most use in more recent times has been for individual panels, particularly non load-bearing ones such as roof panels on vans and trucks - where there is another advantage as an unpainted relatively thin GRP panel is semi-translucent, and so allows light into the load-space, as well as it's light weight lowering the centre of gravity of the vehicle.

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    I suspect the main reason it is not used is that steel is very cheap, very quick to mass produce panels using an automated stamper and can be welded into place quickly. The added weight is just a drawback of mass production and economies of scale. Commented Feb 18, 2016 at 11:11
  • A very good answer. I'm refraining right now from choosing "accepted" one, as each and every one so far is giving me different and valid viewpoint on my question. On side note: i can't find reference to "fiberglass" being a brand name. All I find is "alternative name for GRP". Could you point me in right direction?
    – Koder
    Commented Feb 18, 2016 at 19:58
  • My research suggests that fiberglass is not a brand name, it is just a type of Fiber-Reinforced Plastic. According to Wikipedia, Glass Reinforced Plastic (GRP) is another name for fiberglass. The company Owens Corning patented their so-called "fibreglas" in 1936, which appears to be the German spelling of fiberglass. While that might have been considered a protected name at one point (I have no reason to believe this), fiberglass is not. Commented Feb 18, 2016 at 21:12
  • @PoissonFish I stand corrected... Trying to search for 'fibreglass brand name' just brings up this question!
    – Nick C
    Commented Feb 19, 2016 at 9:46
  • It sure sounds like it should be a brand name. That would have been my guess too. Commented Feb 19, 2016 at 15:17


  • Lightweight.
  • Does not rust.
  • Does not get dents.


  • Breaks/cracks if bent too much.
  • Is not as durable as metal.
  • Can deform with heat.
  • 2
    Simple and clear - perfect. Commented Feb 18, 2016 at 11:31
  • I like the answer as well, but would contend with your second "con": GRF doesn't rust like metal does. I saw one 67 Corvette looked at least "rebuildible" from a body standpoint, but since the car had been sitting in a standing pool of water for 20 years, the bottom half metal components were through. Commented Feb 18, 2016 at 18:49

The major reason is probably cost.

Steel panels need expensive tooling to produce them, but once an investment has been made in that tooling the panels can be produced rapidly and cheaply. Drop in a flat sheet of steel and a few seconds later you have a shaped panel.

With GRP the tooling is relatively cheap, but it takes a long time to produce a panel from that tooling. The matting needs to be cut to shape then laid out (most likely by hand), with overlapping areas carefully aligned, all of which is a relatively skilled job. Some sections will need the 'grain' of the matting carefully aligning. Resin can then be added. To minimise weight (and keep it fairly consistent) the panel will then needing bagging up to suck out the excess resin while it cures, all of which takes time.

Carbon fibre is similar but even more time consuming.

If you are making a few hundred panels then the tooling cost savings of GRP outweigh the high labour costs, but once you get to the thousands the labour costs become uneconomical. Hence GRP bodywork tends to be heavily used for limited production vehicles

I suspect another major consideration now for production vehicles is the ability to recycle GRP panels.

Note that even in the 1950s Lotus put in to production a car with a GRP monocoque body shell with no separate chassis.

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    To add to the first paragraph: panels can be produced rapidly, cheaply, and incredibly consistent with very few variations. Tooling adjustments and repairs can be made quickly reducing downtime. To add to the second paragraph: Another method is blown glass mat. It allows for relatively quick application of material into the mold, but, clean up and accurate application and consistency suffer.
    – Tobin S
    Commented Feb 18, 2016 at 15:56
  • This should be the top answer; all others are simple design issues.
    – Wren
    Commented Jul 7, 2018 at 9:17
  • To add to this answer, a robotic production line with stamped steel panels and spot welding can product hundreds of finished bodyshells in a matter of hours. There is no curing time and little human interaction required. If you've sold a Lotus Esprit, you can take your time building it, if you've sold 20,000 Ford Mondeos, you can't. It's simply a case of steel bodies can be produced in volume in a small amount of space quickly. Commented Feb 20, 2020 at 12:14

One thing that most people neglect to mention is UV stability: even with so-called UV inhibitors, any GRP which is left out in the sunlight will begin to deteriorate: the resins will become brittle and the coloured gel-coat top surface will get spider-web like cracks in it and lose colour. I've seen Lotus Europas that look like they're about ready to disintegrate, just because they've been in the sun for a few decades (and this is much harder to fix than rust) GRP has been popular for a number of decades with kit and low-production manufacturers (in the 50's lotus was very much run like a kit-car company in their methodology) so it is good for low production (tooling and setup) costs.

On the other hand, it's much quicker to have a dedicated steel press hammering out panel after panel, usually at a rate of one or more a second. Glass usually takes a few hours to set or cure before it can be removed from the mould. so on one hand, you can produce car bodies with minimal setup costs (quite a lot of the moulds I"ve used over the years have been made of wood with a layer of glass and gelcoat to give a nice surface to then take mouldings from) vs. the cost of making steel dies for pressing, but then on the other hand, the daily production of bodies in steel will be much higher, which is what the major manufacturers want.

  • The problem here is looking at 43 years' deterioration. No cars are designed for 43 years' endurance.
    – Wren
    Commented Jul 7, 2018 at 9:21

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