I'm glad you think it's useful! Usually try to get these laminate sample videos done in a few hours so the production quality and lack of scripting shows - just trying to pack stuff in to make a useful 5 or 10 minutes.
hey anouther tip: you can use the plug it self- wriggle around on the underside of the aluminium and it will create a perfect round hole for the vacuumhoseplug without using a knife... that saves time
Thanks - I'll have to try that - sounds like a good idea! Just looked at my vacuum connectors and they are rounded and have a little roll pin that goes through a slot where the top pokes through so it may not work as well. Do you use threaded ones?
Yeah it's strange - not sure it's a volatility issue or a thermal issue... or both. Resin CTE may be very different from fiber and fiber just constrains the resin from shrinking in the fiber-axis. I am not 100% on all the mechanics of this so if anybody knows I'd like to learn more! Actually the aluminum tooling may have an impact on this but it happens with carbon tooling too. This is really just to show that it does happen and to watch out for it...
I’ve always been told the mechanism at work here is the CTE mismatch of fiber and matrix at elevated temp cure, as cured laminate cools, stresses develop which propagates the deformation. This is always the example given when discussing laminate schedules and why you want a balanced AND symmetric laminate. My understanding is that the *esters also have this issue because of the same mechanism. Even though they cure at room temp (but seem to be able to be much more exothermic than epoxy!) they have worse CTE characteristics so more extreme shrinkage. Haven’t considered the percent solids part of the equation... would be interested to learn more I think the airplane wing structure being designed asymmetric, was to try to counteract wash(or twist) due to bending for better aerodynamics in its loaded(deformed) state. I’ve heard of people trying this in dinghy Centerboards too. Check your mechanics of materials textbook for bending of asymmetric beams to get a primer on that... then all you have to add is the mechanics of composites stuff! Easy peasy (like how easy it is to draw blood from a stone...) I’d be interested to know what the application was where you wanted an asymmetric laminate to cure flat... There are compensations for CTE of tooling done, so it’s possible. But why try to make a potato chip flat the hard way when you can just use a flat mold and a balanced and symmetric laminate.
I think you're right - and I did a poor job of explaining "thermal stuff" in the video! Lack of scripting had me mumble through those slides. My understanding it that fibers constrain the resin long-way but CTE impacts transverse dimensions to each ply so stresses and warping... And I wish I could get through the engineering - forgot that math long ago! This was just to demonstrate the concept of laminate symmetry and what can go wrong. These samples are supposed to be quick little laminate examples, process demos and illustrations of things that go wrong -all packed together in a hopefully-not-too-confusing way! I try to make enough mistakes to be educational but not so many that it's worthless.
@@ExploreComposites I think you do a great job of toeing the line between practical and the knowledge base behind why things are done a certain way with advanced composites. I really enjoy all your content. The articles on your website are a gold mine! I'm not sure I could walk through the math myself these days... the computer program does a good job though! My other comments were trying to add to the discussion in a few other comments... probably just muddied the waters though. Thanks for putting in all this work to consolidate your knowledge base to share with all of us
Please make a video on how to calculate carbon fiber layers when you have a 3dimensional oart with different thicknesses like an orthotic in-sole (flat at the front, individual at the middle and rather thick at the end).
What about the layers do you want to calculate? Analyzing a tapered or contoured part can be a bit of work - is it the composite properties you're after?
@@ExploreComposites no, in my case it is just the fitting/shape of the part. I would like to precut the layers and with an easy shape like a cube, this would be rather easy (lots of squares). But how many? And when I have like an organic landscape shape, do I need to have a CAD model and slice it in layers? Or could a plaster model, grinded down work as well as an template? And finally my most important question: is there an upper limit for compressing fibers? Could I (theoretically) press 100 layers under a 300 tons press or at which point would the fibers break. Because I saw a video, where they tried to break a (cured) carbon fiber cube under an hydraulic press with many, many layers and they could not break the cube.
So is it impossible to get a flat asymmetrical panel? For example, could you have a mold with that amount of bend in it to counter act the post cure warp?
Yes I think. I read about aircraft designed with unbalanced wing laminates to provide improved strength - or something. With more complicated layups it becomes calculable from a shear perspective too. Search "in-plane extension-shear coupling" - I am not engineer-enough to understand it... forgot my matrix algebra long ago.
You've done a lot of work to present those facts about this material. Thank's a lot!
I'm glad you think it's useful! Usually try to get these laminate sample videos done in a few hours so the production quality and lack of scripting shows - just trying to pack stuff in to make a useful 5 or 10 minutes.
@@ExploreComposites Oh yes, i know about that challenge😉
This is a wonderfully fascinating channel, thanks for sharing your knowledge and experience!
Thanks! Thats a very kind way to describe what is here... going to try to make it more-so if I can find some more time to work on it!
These videos are fantastic, thank you! I'd love to see some tips on using core materials on complex (2-axis) curves if you get the time.
Thanks! Yes, I am working on some non- flat stuff but haven’t had much time lately - definitely part of the plan!
hey anouther tip: you can use the plug it self- wriggle around on the underside of the aluminium and it will create a perfect round hole for the vacuumhoseplug without using a knife... that saves time
Thanks - I'll have to try that - sounds like a good idea!
Just looked at my vacuum connectors and they are rounded and have a little roll pin that goes through a slot where the top pokes through so it may not work as well. Do you use threaded ones?
@@ExploreComposites try it. i use both
Thanks! In the past I have naively assumed that warping shouldn't be an issue when using epoxy resin...because 100% solids. Clearly that isn't true!
Yeah it's strange - not sure it's a volatility issue or a thermal issue... or both. Resin CTE may be very different from fiber and fiber just constrains the resin from shrinking in the fiber-axis. I am not 100% on all the mechanics of this so if anybody knows I'd like to learn more!
Actually the aluminum tooling may have an impact on this but it happens with carbon tooling too. This is really just to show that it does happen and to watch out for it...
I’ve always been told the mechanism at work here is the CTE mismatch of fiber and matrix at elevated temp cure, as cured laminate cools, stresses develop which propagates the deformation. This is always the example given when discussing laminate schedules and why you want a balanced AND symmetric laminate.
My understanding is that the *esters also have this issue because of the same mechanism. Even though they cure at room temp (but seem to be able to be much more exothermic than epoxy!) they have worse CTE characteristics so more extreme shrinkage. Haven’t considered the percent solids part of the equation... would be interested to learn more
I think the airplane wing structure being designed asymmetric, was to try to counteract wash(or twist) due to bending for better aerodynamics in its loaded(deformed) state. I’ve heard of people trying this in dinghy Centerboards too. Check your mechanics of materials textbook for bending of asymmetric beams to get a primer on that... then all you have to add is the mechanics of composites stuff! Easy peasy (like how easy it is to draw blood from a stone...)
I’d be interested to know what the application was where you wanted an asymmetric laminate to cure flat... There are compensations for CTE of tooling done, so it’s possible. But why try to make a potato chip flat the hard way when you can just use a flat mold and a balanced and symmetric laminate.
I think you're right - and I did a poor job of explaining "thermal stuff" in the video! Lack of scripting had me mumble through those slides. My understanding it that fibers constrain the resin long-way but CTE impacts transverse dimensions to each ply so stresses and warping... And I wish I could get through the engineering - forgot that math long ago!
This was just to demonstrate the concept of laminate symmetry and what can go wrong. These samples are supposed to be quick little laminate examples, process demos and illustrations of things that go wrong -all packed together in a hopefully-not-too-confusing way! I try to make enough mistakes to be educational but not so many that it's worthless.
@@ExploreComposites I think you do a great job of toeing the line between practical and the knowledge base behind why things are done a certain way with advanced composites. I really enjoy all your content. The articles on your website are a gold mine! I'm not sure I could walk through the math myself these days... the computer program does a good job though!
My other comments were trying to add to the discussion in a few other comments... probably just muddied the waters though. Thanks for putting in all this work to consolidate your knowledge base to share with all of us
Please make a video on how to calculate carbon fiber layers when you have a 3dimensional oart with different thicknesses like an orthotic in-sole (flat at the front, individual at the middle and rather thick at the end).
What about the layers do you want to calculate? Analyzing a tapered or contoured part can be a bit of work - is it the composite properties you're after?
@@ExploreComposites no, in my case it is just the fitting/shape of the part.
I would like to precut the layers and with an easy shape like a cube, this would be rather easy (lots of squares). But how many?
And when I have like an organic landscape shape, do I need to have a CAD model and slice it in layers? Or could a plaster model, grinded down work as well as an template?
And finally my most important question: is there an upper limit for compressing fibers? Could I (theoretically) press 100 layers under a 300 tons press or at which point would the fibers break.
Because I saw a video, where they tried to break a (cured) carbon fiber cube under an hydraulic press with many, many layers and they could not break the cube.
So is it impossible to get a flat asymmetrical panel? For example, could you have a mold with that amount of bend in it to counter act the post cure warp?
Yes I think. I read about aircraft designed with unbalanced wing laminates to provide improved strength - or something. With more complicated layups it becomes calculable from a shear perspective too. Search "in-plane extension-shear coupling" - I am not engineer-enough to understand it... forgot my matrix algebra long ago.
What peel ply is that?
Pretty sure its Airtech release coated nylon:
compositeenvisions.com/wp-content/uploads/2018/03/Model-511-bleeder-lease-b-tds.pdf