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Thread: Fiber glass strength

  1. #1
    Senior Member Faker's Avatar
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    Fiber glass strength

    I always thought it was very weak. Take a look at this vid, it is stronger then aluminum! Does the foam cause this or is fiberglass just that strong?

    http://www.youtube.com/watch?v=7eUt0...eature=related

  2. #2
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    Re: Fiber glass strength

    Yeah, everybody generally has misconceptions about GRP or glass reinforced plastics. I've worked with kit cars for 35 years now and most people still think about a Vette body as what fiberglass is all about. Cars like that have the body parts as non-stressed pieces that just overlay the structural frame. By using modern cloth and woven materials, better epoxy resins, foam, etc., you can make some pretty tough parts. I made a rear wing for my truck last year from scratch. I started with 1 inch thick polyurethane foam which I carved to shape and kerfed for flex. I then layed up cloth and matt using epoxy resin. My original plan was to use acetone to dissolve the foam core (this is called the "lost foam" casting method) and add steel tubing inside for strength. Once I had laid up all the glass I scratched my head a little and asked my 110 pound grandson to stand on the wing. Didn't dip or deflect one bit. I ended up leaving the foam in which kept my weight down on the part. Wing went all the way across my rear tonneau cover and yet weighed about 8 pounds.
    There are also many, many, more ways to increase the strength of these parts. Vacuum bagging to pull out excess resin and air voids as well as pressurized baking processes can make some lean, mean, composites.

  3. #3
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    Re: Fiber glass strength

    Now that I think of it, I recently saw a crashed Infinity G35 or Nissan 350z at my fathers autobody shop. I dont remember which of the 2 models it was, but they are now using fiberglass for structural parts. The front end of the car (radiator support) was all fiberglass. I wonder if we will ever see a 100% fiberglass car, I mean frame and all.

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    Re: Fiber glass strength

    I just found this post on another forum looking through google. It's a fiberglass frame that looks very close to carbon fiber. Is this the type of fiberglass cloth used? It's some kind of Rc forum, click the pics to see a closeup http://www.rcgroups.com/forums/showt...d4937&t=709746




  5. #5
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    Re: Fiber glass strength

    You should see the new Lotus. I think it is very thin, like the new Corvettes.
    If you're not confused, you're not paying attention.

  6. #6

    Re: Fiber glass strength

    lotus had many all fiberglass or almost all fiberglass cars. wasnt the europa all fiberglass?

    FG is 1/3 the tensile strength of steel but 1/5 the weight, so pound for pound, it's much stronger.
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  7. #7
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    Re: Fiber glass strength

    Like most things, done correctly with appropriate engineering, fiberglass and composites are superior to steel for many applications. That is why there are so many composite parts on aircraft, including fighters. You can't compare some novice produced chopper gun spray-up using general purpose resin with a hand layed or vacuum formed part constructed with a better resin. The difference in strength is night and day. Not always but most of the time you get what you pay for, general purpose resin and chopper gun is cheaper in both material cost and labor to hand layup with an Iso or Ortho DCPD for instance. But the latter is a much stiffer, stronger, and more deminsionally stable. Which can then be layed up thinner and lighter for the same purpose.

  8. #8
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    Re: Fiber glass strength

    With building any fiberglass car, there is always a need to create a steel mounting point, or glass in a steel frame to stiffen the panel. I was constantly buying mat (1.5 oz) from TAP plastics, or similar source. Home depot woven cloth/mat has worked in a pinch. I noticed on Ebay there is a few people on there selling combination dense woven cloth with a mat on the other side. Got 20 lbs of this stuff for almost nothing (compared to home depot at $6 for 3X3 mat). What a deal this stuff is, strong as all get out, harder to cut, but you don't have to put on layer after layer since I think it is almost double the weight of the thin stuff. Couldn't imagine laying up complete panels with this, but if you did I am sure it would be difficult to break when cured. Eric

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    Re: Fiber glass strength

    Yeh we use that stuff for some applications. It is called biaxial. There are many different specs but usually it is two layers of cloth applied at angles to each other, 45 deg or 90 deg, etc with or without a matt stitched in between. You can get triaxial and quad. By the time you get to quad, the only way to get in wetted out is vacuum infused. The other thing it is generally higher spec materials because no one goes to the expense to make a biaxial with bottom end material. I agree with you good stuff. The cheapest place to find it other than e-bay is at www.raka.com. He will sell cut pieces. You can get it cheaper but you have to buy a whole roll.

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