Any stiffness advantage to laying twill layers at 45 degrees to each other?

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Any stiffness advantage to laying twill layers at 45 degrees to each other?

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Steve Broad	Steve Broad posted 5 Years Ago HOT Topic Details
Group: Forum Members Posts: 408, Visits: 4.1K	It says it all in the subject title really :-) I am looking to use two layers of 200gm/m2 3K 2x2 Twill Prepreg Carbon on a project (trying to keep weight to a minimum). Will aligning the layers at 45 degrees to each other increase the stiffness?
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oekmont	oekmont posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 550, Visits: 27K	This is much more compicated than you may think. I will try to give an simplified overview: It depends on the direction you need that stiffness. In the two original directions 0° and 90° the stiffness will decrease, but in the two 45° directions the stiffness will increase, compared to two 0/90 layers. Take a rectangular sheet of carbon with only 0/90 layup. You will find, that is is more rigid if you try to bend it along the edge than from edge to edge. A 0/90/45/-45 sheet of similar thickness will be equally rigid in every direction, but less rigid along the edge than the 0/90 sheet.
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Steve Broad	Steve Broad posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 408, Visits: 4.1K	+x oekmont - 4/12/2020 8:57:08 AM This is much more compicated than you may think. I will try to give an simplified overview: It depends on the direction you need that stiffness. In the two original directions 0° and 90° the stiffness will decrease, but in the two 45° directions the stiffness will increase, compared to two 0/90 layers. Take a rectangular sheet of carbon with only 0/90 layup. You will find, that is is more rigid if you try to bend it along the edge than from edge to edge. A 0/90/45/-45 sheet of similar thickness will be equally rigid in every direction, but less rigid along the edge than the 0/90 sheet. OK, thanks. Everything is always more complicated than I think :-) So, if building a car door or roof which have supported edges with additional layers, the central area would be stiffer with CF laid at 45 deg? Edited 5 Years Ago by Steve Broad
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oekmont	oekmont posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 550, Visits: 27K	If the roof is only attached at the 4 corners, maybe. Car parts are usually konkave anyways. This creates far more stiffness than an additional layer, or the orientation of fibres. The differences will likely be very small
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Steve Broad	Steve Broad posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 408, Visits: 4.1K	+x oekmont - 4/12/2020 5:22:10 PM If the roof is only attached at the 4 corners, maybe. Car parts are usually konkave anyways. This creates far more stiffness than an additional layer, or the orientation of fibres. The differences will likely be very small Cheers. I will keep it simple then. Two layers of 200gm prepreg with strengthened edges and corners to improve rigidity. What could possibly go wrong :-)
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