Material calculator/equation??

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Material calculator/equation??

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speed_demon	speed_demon posted 10 Years Ago HOT Topic Details
Group: Forum Members Posts: 23, Visits: 163	Hello, I have been reading everything I can find about composites but I haven't found any type of equation/calculator for determining composite thickness requirements. I know different resins, etc. have a bearing on the strength but, there's got to be a "safe" relation between how much composite equals the strength of an object made of steel/aluminum. I am trying not to waste too much material and loose the weight saving of making parts out of composites. I'm also not looking to make parts that risk my life on (bike frames, control arms), just automotive body panels, intake manifold or a pickup tonneau cover. I think a formula wouldn't be too hard that would make parts safely 15-20% strong than OEM and still have a substantial weight savings. For example: How thick would a fender need to be if it was made out of e-glass or carbon fiber vs. OEM sheet metal? I know a wheel well would have to thicker to survive a rock from the tire tread at speed, but how thick? Would a layer or two of kevlar add to 2mm of e-glass be good or over-kill? Everywhere I see PSI tensile strength,etc. but does it mean that I would need half the thickness of an aluminum bracket if the fiberglass is twice the metal's strength rating? Thank you for your time, hope to hear back from you soon.
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Trace Elliott	Trace Elliott posted 10 Years Ago HOT Post Details
Group: Forum Members Posts: 4, Visits: 30	As an engineer myself, I join Chris Scott's view. To calculate the required thickness of a particular part, you'll need to compute shape, fibers orientation, and loads. You'll need software that is anything but user-friendly, not to mention ridiculously expensive for an individual (thousands if not tens of thousands of euros). And the months it will take you to learn to use the software could be put to use by making prototypes and testing them. My advice: start by matching the thickness (1mm steel => 1mm CF), and try to understand the way the loading works, to best orient the fibers. For a car bonnet, I'd use mutliple payer of bi-axial (0/90 and 45/-45), changing the orientation for every layer i order to have an near-isotropic part (same strength in all directions, like metallic plates). For a part that is under a tensile load, I'd put more fibers along the length than the width of the part (uni-directional layers interspaced with 45/-45, for instance) When you have a point load, try to include an insert, something to spread the load before it reaches the carbon fiber. Keep in mind that the shape of the part gives it part of its rigidity. A 1mm thick plate might be flexible, whereas a complex shape of the same thickness will be much more rigid. And like all of us, scour the net to find people who have made a similar part, and are kind enough to share the detail of their layup (you hear that McLaren? Tell us how you make your chassis!!)
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