Engineering a new Engineering
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Engineering a new Engineering
I am interested in a discussion of resin/matrix (two-phase) materials in commercial aviation. If this is the wrong time and place, disregard. I have no axe, I have been a proponent since age eight, when (1954) I started using epoxy to build my powered aircraft models.
If a specific topic is necessary, I'd especially be interested if experts in structural components, testing, monitoring and maintenance got involved. If further narrowing is desired, perhaps someone will address the long term challenges in maintenance/repair/new applications.
There are too many myths and mystics imho, it's here to stay, and the better we know it, the better the acceptance of it.
Lyman
If a specific topic is necessary, I'd especially be interested if experts in structural components, testing, monitoring and maintenance got involved. If further narrowing is desired, perhaps someone will address the long term challenges in maintenance/repair/new applications.
There are too many myths and mystics imho, it's here to stay, and the better we know it, the better the acceptance of it.
Lyman
http://aerosociety.com/Assets/Docs/P...5%20COLOUR.pdf
Quite a good paper I thought, although I was utterly incredulous that the referees allowed it to be published without a single reference.
G
Quite a good paper I thought, although I was utterly incredulous that the referees allowed it to be published without a single reference.
G
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Peer Review.
Many thanks Genghis! You broach a traditional snag with composites. There is no lack of engineering re: applications, but there is a profound lack of agreement in the industry. Professionals hesitate to accomodate research in a highly competitive field. Signing on to another's paper can cost gobs of money down the road.
Add to this reluctance the need for critical standards in Aviation, and the myths prolong! I spent my early years watching the politics and the mercenary warfare involved in bringing organic chemistry into the mercantile.
"Propietary". Here is a word that to my mind hampers progress and safety.
The first automotive appearance for "plastic' was 1953. On the water, 1968. Aviation started folding in two phase materials in the early seventies. I continue to be enthralled with the concept; it remains expensive, energy intensive, and "sophisticated".
Safety? Structurally, the material is well received, and the squishy part has to do with survivability in fire, fume, and heat.
Aging is another area that presents some unknowns.
Add to this reluctance the need for critical standards in Aviation, and the myths prolong! I spent my early years watching the politics and the mercenary warfare involved in bringing organic chemistry into the mercantile.
"Propietary". Here is a word that to my mind hampers progress and safety.
The first automotive appearance for "plastic' was 1953. On the water, 1968. Aviation started folding in two phase materials in the early seventies. I continue to be enthralled with the concept; it remains expensive, energy intensive, and "sophisticated".
Safety? Structurally, the material is well received, and the squishy part has to do with survivability in fire, fume, and heat.
Aging is another area that presents some unknowns.
Ageing - which is variably a function of humidity, UV, BVID / microcracking, and fickle fate, and to a lesser extent variability in manufacture, are surely the biggest headaches and the hardest to quantify. Hence the well known composite superfactor in AMC 619.
Every study I've ever seen showing tests to destruction of a range of components, particularly where the failure mode includes substructure buckling, shows massive variability in failure loads - even at start of life - sufficient to make the composite superfactor seem very non-conservative.
G
Every study I've ever seen showing tests to destruction of a range of components, particularly where the failure mode includes substructure buckling, shows massive variability in failure loads - even at start of life - sufficient to make the composite superfactor seem very non-conservative.
G
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Indeed. Per the paper, the standard 1:5 ultimate loading is projected to be alternately decreased (relaxed), and increased, (more strict) dependent on the very questions you pose. The potential for lightening the airframe is large. It will take years to develop these standards, and the headaches you mention in fail/destructive testing will not shorten this time frame.
The upside is the great detail and patience involved in the manufacture itself. The first boat hulls were 3cm thick! One hopes the rebound from caution will not be a relaxation of best practice. I think there will be few "gotchas", the demands will not diminish, especially in aviation.
Had I reviewed the paper, I would have insisted on dropping the comparison to plywood. Duramold is a laminating process, not a layup, per se. Lumber is a two phase material (natural) on its own, and the phenolics are not resin, per se, but adhesive.
I note that the problems predominate in the mating/joining of assemblies, not in the subjacent structures; that is encouraging, and embarrassing at the same time? Eventually, the size of the airframe will moot, either through larger ovens, or in abandoning the piece to piece method, (smaller a/c).
The upside is the great detail and patience involved in the manufacture itself. The first boat hulls were 3cm thick! One hopes the rebound from caution will not be a relaxation of best practice. I think there will be few "gotchas", the demands will not diminish, especially in aviation.
Had I reviewed the paper, I would have insisted on dropping the comparison to plywood. Duramold is a laminating process, not a layup, per se. Lumber is a two phase material (natural) on its own, and the phenolics are not resin, per se, but adhesive.
I note that the problems predominate in the mating/joining of assemblies, not in the subjacent structures; that is encouraging, and embarrassing at the same time? Eventually, the size of the airframe will moot, either through larger ovens, or in abandoning the piece to piece method, (smaller a/c).
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Lyman,
Here is some additional resources for you to read through which addresses some of the issues you have brought up. The first is what the FAA looked at and did regarding the 787 certification process.
http://www.gao.gov/new.items/d11849.pdf
Here is a presentation given by Boeing in Dayton, OH in October 2008 regarding composite testing.
http://academic.udayton.edu/stevendo...ons/Mabson.pdf
Here is a photo of the interior of a fuselage section section similar to section 48
When you talk about strength, here is a reference table
The strength comes from the carbon fiber which is slightly less than 3X the strength of high tensile steel while having a density 4X less when compared to the same steel.
You were correct about delamination. Delamination occurs between the layers of material where the bonding material is present, not across layers, that would be an over tensile strength failure.
One of the reasons you do not find much information about composites is the fact that much of the development work was done by NASA or DARPA for sensitive military aircraft that are currently flying in the USAF inventory. I saw a site that had to do with the subject of reclaiming composite material from the 787 that is not used (the material is expensive) One photo depicted a cross-section of the fuselage composite material (at least that is what they indicated). It would appear there are 14 layers of material bonded together making up the total cross-section.
As far as aging is concerned, remember, all the GE90 fan blades are composite material, not that different from the Boeing material. As you can imagine, they undergo various gyrations during operation, bending, twisting, impacts radial stressing, etc. They have preformed very well, better overall than titanium fan blades. Not many have been discarded except for extreme FOD, birds especially and the most less damaged blades are generally repairable.
More will be learned with the advent of the GEnx engines, the fan casing as well as the fan blades are made from composite material.
Here is some additional resources for you to read through which addresses some of the issues you have brought up. The first is what the FAA looked at and did regarding the 787 certification process.
http://www.gao.gov/new.items/d11849.pdf
Here is a presentation given by Boeing in Dayton, OH in October 2008 regarding composite testing.
http://academic.udayton.edu/stevendo...ons/Mabson.pdf
Here is a photo of the interior of a fuselage section section similar to section 48
When you talk about strength, here is a reference table
The strength comes from the carbon fiber which is slightly less than 3X the strength of high tensile steel while having a density 4X less when compared to the same steel.
You were correct about delamination. Delamination occurs between the layers of material where the bonding material is present, not across layers, that would be an over tensile strength failure.
One of the reasons you do not find much information about composites is the fact that much of the development work was done by NASA or DARPA for sensitive military aircraft that are currently flying in the USAF inventory. I saw a site that had to do with the subject of reclaiming composite material from the 787 that is not used (the material is expensive) One photo depicted a cross-section of the fuselage composite material (at least that is what they indicated). It would appear there are 14 layers of material bonded together making up the total cross-section.
As far as aging is concerned, remember, all the GE90 fan blades are composite material, not that different from the Boeing material. As you can imagine, they undergo various gyrations during operation, bending, twisting, impacts radial stressing, etc. They have preformed very well, better overall than titanium fan blades. Not many have been discarded except for extreme FOD, birds especially and the most less damaged blades are generally repairable.
More will be learned with the advent of the GEnx engines, the fan casing as well as the fan blades are made from composite material.
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to a piceth
Hi Turbine D
Thanks for all your time, a bonanza! When I left composites/manufacture, computers were nowhere near the level they are today. Looking over the Boeing data, I am reminded of a free wheeling discussion. The sense in the group was that at some point, people will realize two phase of all description would eventually teach us how to use it. With advanced modeling, utilizing failure models will lead to reversing the cascade into a manufacturing model that allows eliminating much of the material in a substructure. Stress pathways can be engineered into a piece without the need for so much material. Just as metallic beams can be 'relieved' of material to save weight, so too can composites.
So this brings us to 'monocoque'. Stressed skin can be blended with stiffening members and their attendant spiders to virtually eliminate the need for "fasteners". An economy of strength/weight, as it reaches optimum, will astound us as to the gross weight of the airframe.
The 'barrel' that Boeing shows us (fuselage) serves well as a model. Imagine half that structure gone, replaced with a skin of lapped 'scales'. Instead of circular taping (it is actually "spiral", but functionally circular), appositional helical winding will replace it, each successive layer opposite in direction and bias.
If you have ever seen the chiton skeleton of a turtle, that is instructive. At the dorsal of the carapace is the "Spine", a beautifully distributive structure that supports the entire shell.
Instead of relying on mass/heft, new composites will be sliced, diced, and minimized to provide optimum strength to weight. More than this will be the welcome loss of mechanical fasteners, the source of many problems thus far.
Not a Luddite, but I will welcome also the construction of entire a/c in situ,
rather than dependent on barge, Rail and heavy lifters to co-locate subassemblies.
nice to see you, take care
Thanks for all your time, a bonanza! When I left composites/manufacture, computers were nowhere near the level they are today. Looking over the Boeing data, I am reminded of a free wheeling discussion. The sense in the group was that at some point, people will realize two phase of all description would eventually teach us how to use it. With advanced modeling, utilizing failure models will lead to reversing the cascade into a manufacturing model that allows eliminating much of the material in a substructure. Stress pathways can be engineered into a piece without the need for so much material. Just as metallic beams can be 'relieved' of material to save weight, so too can composites.
So this brings us to 'monocoque'. Stressed skin can be blended with stiffening members and their attendant spiders to virtually eliminate the need for "fasteners". An economy of strength/weight, as it reaches optimum, will astound us as to the gross weight of the airframe.
The 'barrel' that Boeing shows us (fuselage) serves well as a model. Imagine half that structure gone, replaced with a skin of lapped 'scales'. Instead of circular taping (it is actually "spiral", but functionally circular), appositional helical winding will replace it, each successive layer opposite in direction and bias.
If you have ever seen the chiton skeleton of a turtle, that is instructive. At the dorsal of the carapace is the "Spine", a beautifully distributive structure that supports the entire shell.
Instead of relying on mass/heft, new composites will be sliced, diced, and minimized to provide optimum strength to weight. More than this will be the welcome loss of mechanical fasteners, the source of many problems thus far.
Not a Luddite, but I will welcome also the construction of entire a/c in situ,
rather than dependent on barge, Rail and heavy lifters to co-locate subassemblies.
nice to see you, take care
Last edited by Lyman; 26th Feb 2012 at 22:57.
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Hi Lyman,
Glad to have made some contribution to this discussion. In other threads regarding composites in aircraft such as the 787 or the newer A-350, it is amazing to me the negativity that application of new technology seemingly provokes. I always think of these words:
This is what brings about technology advancement in any field, it is a look beyond the horizon...
Glad to have made some contribution to this discussion. In other threads regarding composites in aircraft such as the 787 or the newer A-350, it is amazing to me the negativity that application of new technology seemingly provokes. I always think of these words:
Innovation is an invention with a customer and a marketable vision in mind.
"Visionary" - A person with clear, distinctive and specific vision of the future, usually connected with advances in technology or social/political arrangements.
A vision is a clear, distinctive and specific view of human activities in the future and how those activities might be changed or made better.
Visions combine things
Visions connect things
Visions apply the new to the old
Visions create value propositions
"Visionary" - A person with clear, distinctive and specific vision of the future, usually connected with advances in technology or social/political arrangements.
A vision is a clear, distinctive and specific view of human activities in the future and how those activities might be changed or made better.
Visions combine things
Visions connect things
Visions apply the new to the old
Visions create value propositions
