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Kayak and Canoe Design Bulletin Board
Re: :(
Posted By: Dean Trexel
Date: Wednesday, 3 May 2000, at 9:19 p.m.
: It appears that you are getting in way over your head ...
Nothing is learned unless the material is over your head. I haven't read the materials yet, and wasn't aware that the parallel/series method applied to composites, which is why I posed the rather rhetorical question of how to model the epoxy that looks like swiss cheese when the cloth is ignored. -- thanks for the answer.
: The usual way to model a layered composite is as follows ...
: Make the woven glass cloth into 2 layers of unidirectional cloths. Now along
: the axis of the cloth the epoxy and the fibers carry the load in parallel.
: Perpendicular to the fibers the load is carried by the fibers and epoxy in
: series. For these 2 orientations you can compute a reduced E and solve the
: problem easily. the formulas look like series and parallel electrical
: resistance formulas - The sum of E times the volume % of the material. At
: other angles you wind up with 3 really ugly terms involving sin's and
: cos's raised to the third power. The terms represent the
: tension/compression in the epoxy and the fibers, and the shear in the
: epoxy. Most engineering books on composite design cover the details.: The wood is just another layer of composite material.
: The math is too hard to do by hand. Unless your software can handle
: composites, it will do all the above you, you have no hope of getting the
: properties correct in the elements.
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