UD vs woven Prepreg

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UD vs woven Prepreg

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student00	s student00 posted 7 Years Ago HOT Topic Details
s Group: Forum Members Posts: 15, Visits: 47	I am trying to decide between using UD prepreg vs woven prepreg for a surfboard deck. I am leaning towards using a quad axial prepreg (one UD layer of 0,90,45,-45) as opposed to two layers of bi axial woven prepreg(one woven 0,90 and one -45,45 From my understanding: 1) UD being noncrimp has higher stiffness than woven 2) UD being flat has less chances of having resin rich pockets resulting in a laminate less prone to cracking So essentially a laminate with 2 layers of UD (0,90) would have higher stiffness and lower weight (less resin) than a woven ply (0,90). So it seems like UD would be the more sensible choice, so then why is woven used so commonly? I understand if woven is used instead of one UD as it has fibers in both directions but what about biaxial UD vs woven? Note they are both prepreg, question being wouldnt 2 layers of UD prepreg yield better mechanical properties than one layer of woven prepreg? I look forward to learning!
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Hanaldo	Hanaldo posted 7 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	You would probably be surprised how often axial fabrics are used in structural applications, they are more common than you might think. As for why wovens are more common, it's likely just a supply and demand thing more than anything else - for the average Joe, wovens are easier to work with and still do perform very well mechanically. Personally, making parts for mid to high end race cars, I only use woven materials for my outer layers that have a cosmetic element. All structural components/reinforcement is done with UD and axials. You are at the end of the day somewhat splitting hairs. Yes, UD's and axials have slightly better mechanical performance. Does that really make a difference on something like a surfboard? Possibly not. In aerospace and F1, and other pinnacle level applications, absolutely.
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f1rob	f1rob posted 7 Years Ago HOT Post Details
Group: Forum Members Posts: 237, Visits: 4.8K	Have you actually tried putting U/D down ? It's bloody hard soon as you get near a slight curve. You will be slicing it to get it down an loose most of the strength At the start all the f1 composite chassis were U/D that soon changed an the only U/D you have now is inter laminar in flat/straight runs I.e across the back of the chassis from roll hoop to engine mount Get yourself a 2x2 twill,little bit of heat an that will go round the edges of a board SO easy
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Steve Broad	Steve Broad posted 7 Years Ago HOT Post Details
Group: Forum Members Posts: 408, Visits: 4.1K	+x f1rob - 12/24/2018 9:45:26 AM Have you actually tried putting U/D down ? It's bloody hard soon as you get near a slight curve. You will be slicing it to get it down an loose most of the strength At the start all the f1 composite chassis were U/D that soon changed an the only U/D you have now is inter laminar in flat/straight runs I.e across the back of the chassis from roll hoop to engine mount Get yourself a 2x2 twill,little bit of heat an that will go round the edges of a board SO easy I only use woven as, as you say, U/D can be a pain to work with. Question. If laying down a 3 layer flat sheet using a 2x2 twill, is there any stiffening advantage in laying the centre layer at 45 degrees to the other two?
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student00	s student00 posted 7 Years Ago HOT Post Details
s Group: Forum Members Posts: 15, Visits: 47	How many layers of woven do u use for the deck and the bottom? The resin and the fiberglass are responsible for the stiffness of the board, whereas the foam core is responsible for the compressive strength. Is that correct?
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f1rob	f1rob posted 7 Years Ago HOT Post Details
Group: Forum Members Posts: 237, Visits: 4.8K	+x Steve Broad - 12/27/2018 11:38:33 AM +x f1rob - 12/24/2018 9:45:26 AM Have you actually tried putting U/D down ? It's bloody hard soon as you get near a slight curve. You will be slicing it to get it down an loose most of the strength At the start all the f1 composite chassis were U/D that soon changed an the only U/D you have now is inter laminar in flat/straight runs I.e across the back of the chassis from roll hoop to engine mount Get yourself a 2x2 twill,little bit of heat an that will go round the edges of a board SO easy I only use woven as, as you say, U/D can be a pain to work with. Question. If laying down a 3 layer flat sheet using a 2x2 twill, is there any stiffening advantage in laying the centre layer at 45 degrees to the other two? LOT better in twist an also more balanced
	Reply Like 3
Steve Broad	Steve Broad posted 7 Years Ago HOT Post Details
Group: Forum Members Posts: 408, Visits: 4.1K	+x f1rob - 12/27/2018 12:55:01 PM +x Steve Broad - 12/27/2018 11:38:33 AM +x f1rob - 12/24/2018 9:45:26 AM Have you actually tried putting U/D down ? It's bloody hard soon as you get near a slight curve. You will be slicing it to get it down an loose most of the strength At the start all the f1 composite chassis were U/D that soon changed an the only U/D you have now is inter laminar in flat/straight runs I.e across the back of the chassis from roll hoop to engine mount Get yourself a 2x2 twill,little bit of heat an that will go round the edges of a board SO easy I only use woven as, as you say, U/D can be a pain to work with. Question. If laying down a 3 layer flat sheet using a 2x2 twill, is there any stiffening advantage in laying the centre layer at 45 degrees to the other two? LOT better in twist an also more balanced Cheers.
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