I ca answer your question in two ways...
First, if you are looking to quantify expected impact resistance then I would use one or several of the ABA or ISO composite engineeing tables publically available. however, even with the help of an engineer or engineering tables it will come down to what you can achieve in your build. These charts are based on averages using specific techniques in controlled enviornments. Thus- consult a composite engineer (there are several in these threads) and then increase the laminate fractionally based on your actual success achieved on test pieces.
The second way to answer your question I have found to be MUCH more helpful in the real world. An engineer may or may not be given enough information to provide an accurate analysis. So, build a mock up piece with the lamination technique you intend to employ. Then design a seriesof simple pragmatic tests to destroy them. They should include impact in a small area (using gravity and a weighted rod on end to drop onto the laminate) should show both force applied and the area it is applied to. Then repeat the test with a larger impact area. Increase the force (drop from higher) until you blow it up.
The other two tests that are very important are sheer strength (deflection before structural failure) and static load (where the back side of the laminate is against an immovable object). I used a hydraulic cylinder for these so I could get an accurate read. Be sure to release the load inbetween each pressure application with one piece, and then use a constant increase without release on another.
In the end you are being asked to ACTUALLY build something stronger, and you will learn a lot more about your abillity to laminate and which materials are superior by systematicall killing test pieces. Simply relying on structural analysis from other peoples tests assumes you can achieve thier effeciency and reproduce the enviornment. This can be very, very difficult.
When building a high tech racing dingy I wanted the deck to be able to withstand certain real world ooops'. Like the guy throwing you a beer missing and having it hit the deck. You don't want it to ding like a surfboard even if the engineer tells you that all you need is 8oz of S glass- a test piece of 1208 biax over 80h foam with a 4oz s glass veil took repeated hammer strikes quite well for an increase of roughly 7% in my ACHIEVED laminate. Thus, more was better. If it dinged just the same I would have looked at foam density, resin content, and glass structure- one at a time. Find the combo that works and then employ it!
11-29-2010, 07:16 AM
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