Fiberglassing Plywood for Impact and Stiffness

[Ed3]

Just looking for a little clarification on the utilization of fiberglass and it's application here.

In looking at the Gougeon Brothers data on impact testing and the location of reinforcing fabrics in wood/composite construction, their conclusion points out that the best location for fabrics is toward the backside of a panel (one application being on the interior of a hull skin). Does this suggest the following would be true.?

If a 2' x 2' piece of Okoume ( 6mm for example ) was bonded to a 2' x 2' x 3/4" frame, It would be easy to stomp on it with "X" amount of force and break through. If you were to cover only one side of the plywood (eg. 6oz. plain weave E-glass), Optimum impact resistance and stiffness would be achieved with the fiberglass applied to the underside of the plywood.

Correct?

Although simple "beam" test with a narrow strip of glassed plywood would verify my understanding, I am too lazy this morning, but energetic enough to give the most convoluted scenario for such a simple question.

[mongo75]

I believe you are correct. I'm no physicist, but you could see how a well bonded piece of glass underneath will in effect "hold' or "catch' the wood trying to break through, whereas a piece on top would help some, but in the end it would basically be holding two broken pieces together like a hindge. However, you could always build up enough layers on the top to where it would be stronger than the one piece on the bottom, in essence makin the wood just a mold.

[Ed3]

Originally Posted by mongo75

I believe you are correct. I'm no physicist, but you could see how a well bonded piece of glass underneath will in effect "hold' or "catch' the wood trying to break through, whereas a piece on top would help some, but in the end it would basically be holding two broken pieces together like a hindge. However, you could always build up enough layers on the top to where it would be stronger than the one piece on the bottom, in essence makin the wood just a mold.

Exactly!. Compression vs. tension. FG strongest in tension and stronger than the plywood.

[the1much]

what are you trying to make impact res.?,,the glass or the ply?,,and doesnt that matter to where things should be (fg on top or bottom,,and isnt "impact" different then "standing" on something? and couldnt raise the impact res.,,and not raise the tension strength of the piece?,,,