Stainless Steel or Aluminum and Fiberglass Connections 1

[openam]

I have some fiberglass panels that need to be attached to an aluminum frame. I was hoping to embed aluminum brackets into the fiberglass and then mechanically fasten the brackets to the aluminum frame.

1) Is there a problem with the expansion ratios of fiberglass and aluminum?

2) If yes, would it be acceptable to use Stainless Steel brackets, or do they have the same problem with expansion/contraction differences?

I've seen regular 14 ga steel brackets embedded into fiberglass in some applications, so I'm thinking that the embedded Stainless Steel wouldn't be a problem, except that it cost 5 times as much.

3) Is there less of a problem if the brackets are only 3" as opposed to a continuous embedded bracket?

 

[MotorCity]

openam,

I have worked with fiberglass panels a few times before in water treatment applications. Fiberglass does not experience thermal expansion as much as aluminum or stainless steel. This is because it is an insulator whereas the metals are conductors with respect to heat. So there is definitely a difference in expansion. If you want a numerical answer you will need to obtain and compare the coefficent of thermal expansion for those materials.

One thing that is always a concern for pultruded fiberglass products is unraveling of the fibers whenever it is cut, drilled, or the epoxy resin surface is penetrated. If this is just an "off the shelf" plexiglass material from the hardware store it should not be a problem.

A final note, I'm surprised to hear that stainless is more expensive. Here in Detroit its just the opposite, fiberglass is more expensive.

Good Luck.

 

[openam]

Motorcity,

I do need to try and find the values for Fiberglass. This might be a problem, because it's going to be hand layed up fiberglass. The brackets were going to be embedded into the resin of the fiberglass during construction of the panel. If anyone knows where to find such values for hand layed up fiberglass it would be greatly appreciated.

On another note I didn't mean that the stainless was more expensive than fiberglass. I ment that the stainless was more expensive than the aluminum. The aluminum and stainless are the two options that I have for brackets, unless someone has any better suggestions.

Thanks,
Mike

 

[Ron]

The CTE for fiberglass lay-up will be somewhere around 8 micro inches/inch per deg F. Correspondingly, for stainless steel it is about 25 percent higher and for aluminum, about 70 percent higher....so stainless steel is closer. Unless you will experience significant temperature swings, I wouldn't worry about that. Use either.