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View Full Version : How to: Working with Fiber Reinforced Plastic(FRP)



Adrian Avgerinos
12-04-2004, 12:34 AM
FRP parts are fast, easy to make, and relatively strong. Here is a quick rundown on how to make FRP parts:

To start you need a mold. This mold can be positive or negative. In my case I will be making a airbox to cover my open element filter in my engine bay, and this will be using a positive mold that will also act as a permanent base for the fiberglass. I chose cardboard as it is cheap and works very well:

http://img.photobucket.com/albums/v232/sbcelicagt/Celica%20V6/IM002603.jpg

I will be working with fiberglass though carbon fiber is very similar in application. There are two kinds of fiberglass, one looks like a woven cloth, the other looks like a brillo pad. The woven cloth type is stronger but harder to apply.

To apply to a part that you do not intend to remove, I have found that 3M spray adhesive rocks! Simply spray the adhesive onto the surface and lay the cloth over the tacky material:

http://img.photobucket.com/albums/v232/sbcelicagt/Celica%20V6/IM002604.jpg

As the inside of the box was harder to apply I chose to use the other form of fiberglass:

http://img.photobucket.com/albums/v232/sbcelicagt/Celica%20V6/IM002605.jpg

Once it dries you can apply the second part of the material: The plastic. It is basically a two part(adhesive and resin) epoxy that must be mixed prior to application.

Adrian Avgerinos
12-04-2004, 12:36 AM
http://img.photobucket.com/albums/v232/sbcelicagt/Celica%20V6/IM002608.jpg
http://img.photobucket.com/albums/v232/sbcelicagt/Celica%20V6/IM002609.jpg

I applied the goop using a small paint brush. A dabbing motion seems to work best. Apply to one side and let dry before flipping over to apply to the second side.

The advantage of the cardboard is the plastic will soak into the cardboard and provide further strength.

After drying it is now time to paint:

http://img.photobucket.com/albums/v232/sbcelicagt/Celica%20V6/IM002612.jpg
http://img.photobucket.com/albums/v232/sbcelicagt/Celica%20V6/IM002613.jpg

See the following websites for additional tips on fiber glassing:
http://web.njit.edu/~cas1383/proj/main/
http://forums.caraudio.com/vb/showthread.php?t=38665

Luni
12-04-2004, 12:45 AM
Thats awesome dude.

Thanks for sharing that.

Playfortoday
12-04-2004, 02:16 AM
If you want to take it a step further, snad the fg, skim the fg with body filler/bondo and sand and repeat until smooth. Prime and paint. :D

Fenix
12-04-2004, 03:42 PM
I'm sure that this airbox is very functional and provides a good seal but i can't say that I approve of your methood.

But first let me get this straight.
You made a cardboard "mold" wich you then covered in Carbon Fiber (b.t.w. Carbon fiber is not fiberglass) and laid the inside with fiberglass. So your "mold" is a part of the box?

Well, i know that i'm sort of a perfectionist when it comes to FRP (especially carbon fiber) and I really don't like the texture of this box. I just hate to see carbon fiber this way, sorry.

slvrblt
12-04-2004, 04:56 PM
i would have used the cardboard as a template to cut pieces of fiberglass honeycomb material.

DrPaine
12-04-2004, 05:18 PM
Dispite his methods, at the performance shop I work at, we have done quite a few SEMA show cars and really, his methods arent that bad at all. The only steps he skipped to make it a great show piece is what play said, sanding it, body filling it and sanding againg till its smooth and then painting and clear coating. But again he isnt looking for a show winning piece, he is goign for functionality.

And one method of laying carbon fiber is similar to this step, I just depends on how u want to use it. Normally when I lay CF, i dont use cardboard but it can be an option. Just depends on how much support you will need.


Good job man. Continue to make post's like this, this is all great stuff, Im always up for learning how other people do fiberglass so maybe I can learn a new trick or two. :bigthumbu

Adrian Avgerinos
12-04-2004, 07:15 PM
I'm sure that this airbox is very functional and provides a good seal but i can't say that I approve of your methood.

But first let me get this straight.
You made a cardboard "mold" wich you then covered in Carbon Fiber (b.t.w. Carbon fiber is not fiberglass) and laid the inside with fiberglass. So your "mold" is a part of the box?

Well, i know that i'm sort of a perfectionist when it comes to FRP (especially carbon fiber) and I really don't like the texture of this box. I just hate to see carbon fiber this way, sorry.

No, it was fiberglass. Both sides. As I said, you can purchase fiberglass as a woven or non-woven format.

The cardboard acts as a mold but is mainly to add strength and additional thermal insulation. The further you distant your outer laments from each other, the greater the strength. For this to have the same strength and stiffness it does now I would have had to lay atleast 4-5 layers and for what gain?


i would have used the cardboard as a template to cut pieces of fiberglass honeycomb material.

Thats fine and dandy except that would make the box too thick and would increase the cost of the project 2 or 3 fold for what gain?

If strength was really an issue I would have used aluminum honeycomb (http://www-cdr.stanford.edu/dynamic/linear_engine/mechanical/energy_absorb/honeycomb.jpg) as the base.

It would be quite simple to make the box plenty pretty as well. Simply spend a few hours sanding down the large lumps on the outside and apply one layer of carbon fiber in the same fashion with a final covering of 2 or 3 gel coats.

Not exactly critical and it doesn't look horrific at this point.:)

Schmleff
12-04-2004, 07:35 PM
There are so many ways to skin the frp cat. One person will not do it the way the next will.

I suggest that the rest of you guys do a write up on your methods. That way we can see the differences between methods, and this is not going to start a composite war :hihi:

Playfortoday
12-04-2004, 09:46 PM
Thats fine and dandy except that would make the box too thick and would increase the cost of the project 2 or 3 fold for what gain?

Guys, I can not agree with Adrian more on this. Before we learned proper methods, we would almost lose money on fiber glass jobs. The materials are extremely expensive when you use them incorrectly. And Adrian, mad props to you. I was not criticizing. I was merely pointing out to the other guys that it can be taken further. Personally, I would have left mine in the same state that you did yours, because I am ALL about go, and I could give a poop less about show. The only thing different that I would have done differently would have been to use foil over my template, and the pealed the shell from my template rather than have the cardboard suck up more costly resin. I don't think strength is an issue on a non-load bearing application. I give you mad fuggin props, and I will be using your write up to inspire my project :) My sticking point is that my airbox needs to be easily removable, because I have my main batt relocation and alt fuses right in front of and next to the strut tower under the fender lip. How easy is it to unistall/reinstall it?

Edit: I thought you used foil in your picture, but it was just a reflection. Updated cooments to reflect that.

Adrian Avgerinos
12-04-2004, 11:34 PM
It's very easy to remove. I have it held in by Velcro. :)

carlosfandango
12-07-2004, 10:31 PM
Hmm, good effort. The wool delaminates under heat and becomes brittle. Fibreglass cloth comes in rolls, like fabric and can be purchased in various thicknesses. the thicker the fabric, the harder it is to shape into difficult angles or arches, so many layers of thinner cloth would have been ideal for this application. Also, it would be much stronger and have a higher heat resistance to delamination. Which type of resin did you use?

to attain a smooth surface, peel ply is used as the final layer, it also draws excessive resin from the item your are fabricating and when peeled off, leaves a smooth surface ready for painting.

Feel free to pm or email me for more info, I was a professional fabricator in the military.

Schmleff
12-07-2004, 11:13 PM
Hmm, good effort. The wool delaminates under heat and becomes brittle. Fibreglass cloth comes in rolls, like fabric and can be purchased in various thicknesses. the thicker the fabric, the harder it is to shape into difficult angles or arches, so many layers of thinner cloth would have been ideal for this application. Also, it would be much stronger and have a higher heat resistance to delamination. Which type of resin did you use?

to attain a smooth surface, peel ply is used as the final layer, it also draws excessive resin from the item your are fabricating and when peeled off, leaves a smooth surface ready for painting.

Feel free to pm or email me for more info, I was a professional fabricator in the military.

Were you guys working with boron? Nasty stuff!

I tried the teflon peal ply on a project last year and have not gone back. Nice stuff, worth the money.

Mister2T
12-15-2004, 05:36 AM
so what material are you guys using to lay the glass on?