Structural design

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Structural design

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Sebasan	S Sebasan posted 7 Years Ago HOT Post Details
S Group: Forum Members Posts: 4, Visits: 93	+x MarkMK - 8/30/2018 9:56:10 AM +x Sebasan - 8/29/2018 8:01:58 PM I'm working in a carbon fiber back seat for a recumbent bicycle and I'm wondering how thick the ribs need to be. The idea is to make it in 2 parts. The outside part which is basically cosmetic and the inside which is the structural part. Them bounded together. The problem is I have no idea how strong carbon fiber really is. I'm thinking about making each rib about 10mm thick (15 layers of 6K) Is this something reasonable? By the way, the dimensions in the PDF are in inches. Thanks I've not been able to view your attachment on the 'phone, but it feels like building solid ribs might be unecessary on something like a seat and it would, no doubt, add a fair bit of weight in your suggested lay-up Two relatively lightweight skins bonded together would give you quite a stiff and strong structure alone. Adding hollow ribs to the reverse skin would add even greater stiffness and would probably deliver the strength (assuming that they're well designed) and stiffness you're looking for. On something like a reclined seat something like a lay-up of 1 x 200g and 1x 650g twill on both skins might be a good start point, with localised additional reinforcement around any particular areas of stress as deemed beneficial. If there's little side to side stress envisaged, then hollow ribs built into the reverse skin running up the back section feels like they'd help cope with the rider's weight well but additional lateral contours might also be a worthwhile consideration Might be worth looking at how most grp bucket seats as used in kit cars etc. are made (in two bonded skins) to get some basic ideas? Thank you Mark, I'm going to follow your advice
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MarkMK	MarkMK posted 7 Years Ago HOT Post Details
Group: Forum Members Posts: 338, Visits: 2K	+x Sebasan - 8/29/2018 8:01:58 PM I'm working in a carbon fiber back seat for a recumbent bicycle and I'm wondering how thick the ribs need to be. The idea is to make it in 2 parts. The outside part which is basically cosmetic and the inside which is the structural part. Them bounded together. The problem is I have no idea how strong carbon fiber really is. I'm thinking about making each rib about 10mm thick (15 layers of 6K) Is this something reasonable? By the way, the dimensions in the PDF are in inches. Thanks I've not been able to view your attachment on the 'phone, but it feels like building solid ribs might be unecessary on something like a seat and it would, no doubt, add a fair bit of weight in your suggested lay-up Two relatively lightweight skins bonded together would give you quite a stiff and strong structure alone. Adding hollow ribs to the reverse skin would add even greater stiffness and would probably deliver the strength (assuming that they're well designed) and stiffness you're looking for. On something like a reclined seat something like a lay-up of 1 x 200g and 1x 650g twill on both skins might be a good start point, with localised additional reinforcement around any particular areas of stress as deemed beneficial. If there's little side to side stress envisaged, then hollow ribs built into the reverse skin running up the back section feels like they'd help cope with the rider's weight well but additional lateral contours might also be a worthwhile consideration Might be worth looking at how most grp bucket seats as used in kit cars etc. are made (in two bonded skins) to get some basic ideas?
	Reply Like 2
Sebasan	S Sebasan posted 7 Years Ago HOT Topic Details
S Group: Forum Members Posts: 4, Visits: 93	I'm working in a carbon fiber back seat for a recumbent bicycle and I'm wondering how thick the ribs need to be. The idea is to make it in 2 parts. The outside part which is basically cosmetic and the inside which is the structural part. Them bounded together. The problem is I have no idea how strong carbon fiber really is. I'm thinking about making each rib about 10mm thick (15 layers of 6K) Is this something reasonable? By the way, the dimensions in the PDF are in inches. Thanks Attachments Ribs analysis Drawing v1.pdf (136 views, 196.00 KB)
	Reply Like 3