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How strong actually is carbon fibre?

Old 09-13-21, 10:13 AM
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Originally Posted by Hondo6
A Tour de France racing frame will have very different design criteria than does one intended for consumer use over multiple decades - or it should, in any case. The TdF frame only has to last a month, maybe 3 or 4 if it's used for training prior; a consumer frame should last considerably longer than that.
I have the same Time VX Special Pro frame ridden by the Bonjour team in the 2003 TdF, which I bought new. I still ride it regularly.

World Tour riders subject their machines to a tremendous amount of abuse, and push them to the limits. It makes no sense to build a frame with a shorter intended life span, and possibly endanger the riders, especially since the bikes are already bumping up against the UCI minimum weight limit. As I understand it, most pros are on the same couple of bikes for a full year, not just a few months.
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Old 09-13-21, 10:24 AM
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Originally Posted by Hondo6
It does, but only gives a partial and misleading picture of reality.

Tensile strength and modulus are only two important factors for a bike frame material. Both are very important, but others - ductility, elongation, "toughness" (defined by Nichols as "the ability to absorb energy by deforming plastically before fracturing"), compression strength, and the material's fatigue limit - are also very important when it comes to a bike's frame. The article you quoted doesn't address them. That's probably because except for fatigue limit (not sure about carbon in that area), carbon doesn't exactly shine in those areas. Those limitations also have to be considered and addressed.

Here's an example: as Nichols points out, monocrystalline silicon (the substrate used for many electronic components, like microprocessors) is vastly superior to aluminum in a number of areas. If you only focused on those good properties, you'd think it's a great choice for a bike frame.

Unfortunately, it's also brittle as hell (low elongation and not "tough" as Nichols defines the term). So it's pretty much useless for building frames.

Bottom line: you can make many things look "perfect" if you focus exclusively on the things they do well while not mentioning the areas in which they don't. But proper design demands that all essential factors be considered and any shortcomings addressed - otherwise you're deluding yourself.

Carbon is a good frame material, with limitations that must be addressed. The same is true of steel, aluminum, and titanium. Great frames and absolute dogs can be made from all four - and with "mix & match" combinations (carbon forks on new titanium frames seem to be effectively standard equipment these days).

And what's "great" and what's a "dog" depends on the intended use. A Tour de France racing frame will have very different design criteria than does one intended for consumer use over multiple decades - or it should, in any case. The TdF frame only has to last a month, maybe 3 or 4 if it's used for training prior; a consumer frame should last considerably longer than that.

Or, in other words: perfect solutions and materials don't exist; there are always trade-offs. (smile)
^ The first cogent response to a thread begun with a silly question. That's why the question would have been better posed on a forum with folks degreed and experienced in the mechanics of materials. Ugh. [slaps forehead and stares at ground]
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Old 09-14-21, 04:55 AM
  #28  
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Originally Posted by Eric F
I have the same Time VX Special Pro frame ridden by the Bonjour team in the 2003 TdF, which I bought new. I still ride it regularly.

World Tour riders subject their machines to a tremendous amount of abuse, and push them to the limits. It makes no sense to build a frame with a shorter intended life span, and possibly endanger the riders, especially since the bikes are already bumping up against the UCI minimum weight limit. As I understand it, most pros are on the same couple of bikes for a full year, not just a few months.
Several problems with this comment.

First: the fact that your frame has lasted 15 years or so is irrelevant. Your model frame may or may not have been designed for a long service life. The fact that it has lasted this long argues that it was - but that's no guarantee; you might simply have been lucky to date. It also tells you nothing about the typical TdF frame - which was doubtless designed by a different designer using different design criteria than yours.

Second: the UCI weight limit is around 20 years old. When it was first imposed, it arguably made sense in terms of safety; carbon construction was then not as well-established as it is today, and there was a plausible concern that the "race to the bottom" in terms of weight would cause designers to go too far in terms of weight reduction. However, it no longer makes sense due to materials advances since 2001. Numerous complete bikes are being sold today to consumers that are lighter than the UCI limit. They have zero safety issues. In fact, for some TdF riders teams actually have to add weight to existing bikes in order to meet UCI criteria, particularly for mountain stages.

Yes, the UCI limit must be followed. That doesn't mean it's still relevant or technically appropriate, other than the fact that it's a rule to be followed.

Third, you don't seem to understand the concept of a fatigue limit and it's impact on design. For materials with a fatigue limit, best data indicates that there is a threshold below which repeated stress can never cause fatigue failure. Steel and titanium are two such materials (though there is some thought to the contrary about titanium, it's still generally accepted to have a fatigue limit). Design structures made from them to be strong enough, and barring a flaw in fabrication or a design error they will not fail from fatigue stress falling within design limits. Ever.

In contrast, both AL and CF have no fatigue limit. This means that repeated stresses from normal use - even small ones, like road bumps - will eventually cause structures made from them to fail. (The exact number of repeated stresses of a given magnitude that will cause failure cannot be predicted exactly, but can be roughly estimated.) That's true even for normal use causing only stresses falling within design limits (anything can be damaged by stresses outside design limits).

Designers using these materials get around this by overbuilding the structure - e.g. ,they make it far stronger than absolutely necessary. How much stronger? That depends on the intended life span and the safety margin desired. No way around that; it's the nature of the material. But CF and AL have very low density, so it's feasible to use more material than the minimum necessary to make them stronger (and thus last longer in routine use) while still getting a light structure. How long the structure can be expected to last in routine use thus depends at least in part on how much extra material over and above the minimum necessary is used.

Fourth: can't speak to current pro team practices. But I'd guess any TdF team would gladly buy a TdF winner a new frame in exchange for a TdF win. And pro athletes are hugely willing to accept risk when it comes to winning - just look at the number of pro athletes (all sports, not just cycling) who still test positive for PED use today. The psychology of the pro athlete (faster/higher/stronger/I'm invincible!) all but guarantees that. So I'm guessing many if not most pro riders would willingly take huge risks if they thought those risks gave them a competitive edge. That would include using a frame that cut safety margins rather close. My understanding is that concern is a big part of what led to the UCI weight limit for bikes in the first place.

Finally: even when adhering to the UCI weight limit, saving weight in the frame gives the total system (bike) designer more flexibility. Weight saved in that area can be used elsewhere - e.g., electronic shifting, beefier and better brakes, etc . . . ). Design flexibility is always a good thing; it almost always leads to a better overall system.

Hey, I'm glad your frame - which I'd bet is CF - has lasted 15 years. But I stand by what I said: a TdF frame has different necessary design criteria than consumer frames, in part because it does not need to last as long. If it lasts a year, that's 3-4 times longer than it actually needs to last. And with CF (and other materials without a fatigue limit), intended normal lifetime impacts the design. Due to the nature of the material, there's no way around it.

Last edited by Hondo6; 09-14-21 at 05:33 AM. Reason: Correct typo, change wording, add phrase.
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Old 09-14-21, 05:07 AM
  #29  
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Originally Posted by Bob Ross
^^^Fair point. Plus I recognize that CF layup technology has advanced significantly since 1977. But I would think surviving the occasional impact with space dust and/or micro-meteors @ 35,000mph might still be reason enough to convince recreational cyclists that the chance of their frame asploding while JRA is misguided.
Depends on the size of the impacting object and the impact location. Bigger ones would be like getting hit with a rifle bullet or worse. Since there are zero aerodynamic forces in space and no gravity to speak of, the structure might or might not survive the impact relatively intact and continue to function. But these would be exceedingly rare, and I'm guessing that risk is considered acceptable and not a major design consideration.

Dust and micrometeoroids are a different story. NASA has rather extensively studied damage from space debris, including dust/micrometeorioid impact effects and risk. The damage to spacecraft from the latter category has been found to be akin to sandblasting. And it's apparently a very slow sandblast process - outside the asteroid belt and the immediate vicinity of planets, interplanetary space is apparently quite empty. (smile)

https://www.nasa.gov/pdf/188970main_...ace_Debris.pdf

Effectively, it appears that the small stuff normally causes only surface pitting. I'm no expert in spacecraft design, but it seems it would be easy to account for that threat by overbuilding the mast to include a sacrificial outer layer of sufficient thickness to account for the expected damage plus a safety factor. Using carbon fiber composite, I'm fairly that wouldn't be weight-prohibitive. And there may be even more effective ways to protect an object from such damage in space; dunno.

Or in other words: consider the possible shortcomings of the material being used and design accordingly - just like good bike frame makers do. (smile)

Last edited by Hondo6; 09-14-21 at 05:17 AM. Reason: Add info omitted in original and correct typo.
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Old 09-14-21, 10:56 AM
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Originally Posted by Steve B.
The Boeing 787 fuselage is composite and carbon fiber. As far as I can determine, there have been no issues with this design
But as I have posted before the French Airbus airplanes have had the vertical tail section and rudder break off at least 3 planes, killing several hundred people. Some senior pilots wont fly an Airbus or let their families fly on them.
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Old 09-14-21, 11:13 AM
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Originally Posted by rydabent
But as I have posted before the French Airbus airplanes have had the vertical tail section and rudder break off at least 3 planes, killing several hundred people. Some senior pilots wont fly an Airbus or let their families fly on them.
What does this have to do with CF bicycle frames?
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Old 09-14-21, 11:18 AM
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Originally Posted by Hondo6
Depends on the size of the impacting object and the impact location. Bigger ones would be like getting hit with a rifle bullet or worse. Since there are zero aerodynamic forces in space and no gravity to speak of, the structure might or might not survive the impact relatively intact and continue to function. But these would be exceedingly rare, and I'm guessing that risk is considered acceptable and not a major design consideration.

Dust and micrometeoroids are a different story. NASA has rather extensively studied damage from space debris, including dust/micrometeorioid impact effects and risk. The damage to spacecraft from the latter category has been found to be akin to sandblasting. And it's apparently a very slow sandblast process - outside the asteroid belt and the immediate vicinity of planets, interplanetary space is apparently quite empty. (smile)

https://www.nasa.gov/pdf/188970main_...ace_Debris.pdf

Effectively, it appears that the small stuff normally causes only surface pitting. I'm no expert in spacecraft design, but it seems it would be easy to account for that threat by overbuilding the mast to include a sacrificial outer layer of sufficient thickness to account for the expected damage plus a safety factor. Using carbon fiber composite, I'm fairly that wouldn't be weight-prohibitive. And there may be even more effective ways to protect an object from such damage in space; dunno.

Or in other words: consider the possible shortcomings of the material being used and design accordingly - just like good bike frame makers do. (smile)
Unrelated to bike frames of CF material....My dad was a design engineer at JPL involved with the Galileo project in the mid-late '80s. His team was responsible for the design and construction of the "space blankets" that protect sensitive parts of the spacecraft from debris during its voyage. Obviously, there are some exposed parts, but space debris is a definitely a concern.
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Old 09-14-21, 11:32 AM
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Originally Posted by rydabent
But as I have posted before the French Airbus airplanes have had the vertical tail section and rudder break off at least 3 planes, killing several hundred people. Some senior pilots wont fly an Airbus or let their families fly on them.
American Airlines flight 587 had a failure of the carbon fiber vertical stabilizer that was not an actual failure of the material, but the bolts and assembly that held the tail to the fuselage. The failure was a result of Airbus's lack of movement limiting in the steerable section of the tail that subsequently caused the stabilizer to separate from the plane The co-pilot, having encountered severs vortices from a flight that had taken off before them, over corrected with the vertical stabilizer mechanism (itself a result of improper training), and caused the rudder mechanism to exceed design load. Likely would have happened if the tail was aluminum. Nobody ever blamed the use of carbon fiber.
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Old 09-14-21, 12:16 PM
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Originally Posted by rydabent
But as I have posted before the French Airbus airplanes have had the vertical tail section and rudder break off at least 3 planes, killing several hundred people. Some senior pilots wont fly an Airbus or let their families fly on them.
Correction;
Airbus is a European consortium, not a French Company.
The last tail separation was in 2009 and some pilots believe the world is flat.
The tail separations were not linked to the use of composites but rather an issue with the controls and flight computer.
This Aircraft was designed in 1971 and stopped production in 2007

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Old 09-14-21, 12:17 PM
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Originally Posted by Hondo6
I stand by what I said: a TdF frame has different necessary design criteria than consumer frames, in part because it does not need to last as long. If it lasts a year, that's 3-4 times longer than it actually needs to last. And with CF (and other materials without a fatigue limit), intended normal lifetime impacts the design. Due to the nature of the material, there's no way around it.
The challenge I have with this is that the same frames that are used by World Tour riders are available to consumers. There may be the occasional one-off custom (certainly custom paint, but that's not what we are talking about), but manufacturers are not making special frames for every rider, for just one event. It makes no sense that a frame built from a material with an infinite fatigue life, that can endure the demands of racing for 3 weeks at the highest levels, will have a sudden drop-off of durability and performance shortly afterwards.

Originally Posted by Specialized
Composites do not behave like metals. In fact, they don’t actually fatigue like metals in the same classic sense of the word. The fatigue life of the fibre itself is just about infinite.
Originally Posted by Kestrel
...carbon composites themselves are not subject to fatigue failures as metals are. So the fatigue life of a properly made carbon composite is “infinite”.

Originally Posted by Enve
If you look at carbon materials in general, they’re very good in fatigue, much better than any aluminium or steel would be. If done properly, a frame could last you forever.
I know quite a few people who ride on pro-level CF frames of varying ages, including a couple that were actually ridden in the TdF. They continue to perform just as they always have. My experience with my old CF frame is not unusual or lucky.
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Old 09-14-21, 01:52 PM
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Originally Posted by Eric F
Unrelated to bike frames of CF material....My dad was a design engineer at JPL involved with the Galileo project in the mid-late '80s. His team was responsible for the design and construction of the "space blankets" that protect sensitive parts of the spacecraft from debris during its voyage. Obviously, there are some exposed parts, but space debris is a definitely a concern.
Sounds like they ended up using something akin to Whipple sheilds and/or improved versions of same. That would have been my guess as to the next step beyond a sacrificial outer layer (or maybe in place of same). Makes sense.

Your dad apparently did a good job. As I recall, Galileo lasted well beyond its design lifetime and ended up being intentionally de-orbited into Juipter's atmosphere.

Not downplaying concerns about space debris. My understanding is that it's definitely a concern during launch and while in earth orbit. We (mankind) have put up a lot of "junk" that remains in orbit hazarding anything launched. But I also understand that threat goes way down once you get out of the vicinity of the Earth.

Still: there's a limit to what can be done in the way of providing protection for, well, anything if you want the resulting item to be usable. Some very low-probability risks simply have to be accepted because avoiding them entirely and/or protecting against same just isn't feasible.

Last edited by Hondo6; 09-14-21 at 02:06 PM. Reason: Add additional info.
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Old 09-14-21, 02:10 PM
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Originally Posted by Hondo6
Sounds like they ended up using something akin to Whipple sheilds and/or improved versions of same. That would have been my guess as to the next step beyond a sacrificial outer layer (or maybe in place of same). Makes sense.

Your dad apparently did a good job. As I recall, Galileo lasted well beyond its design lifetime and ended up being intentionally de-orbited into Juipter's atmosphere.

Not downplaying concerns about space debris. My understanding is that it's definitely a concern during launch and while in earth orbit. We (mankind) have put up a lot of "junk" that remains in orbit hazarding anything launched. But I also understand that threat goes way down once you get out of the vicinity of the Earth.

Still: there's a limit to what can be done in the way of providing protection for, well, anything if you want the resulting item to be usable. Some very low-probability risks simply have to be accepted because avoiding them entirely and/or protecting against same just isn't feasible.
I wasn't challenging your input on space debris, just contributing to it from my small sliver of knowledge on the topic ( I was in HS at the time my dad was involved with the project). Galileo wrapped up in its space suit...
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Old 09-14-21, 03:32 PM
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Carbon passes my test - it is strong enough to open a beer bottle

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Old 09-14-21, 05:40 PM
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Originally Posted by Eric F
What does this have to do with CF bicycle frames?
about as much as saying airplanes and spacecraft masts are carbon so bikes should be ok
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Old 09-14-21, 06:45 PM
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Originally Posted by amokeu
I often see stuff regarding how strong carbon fibre is, but I also see stuff about how risky carbon is as its literally fibre networks, I'm assuming its much stronger than aluminium, however whats the chances something happens, around the same as aluminium bending? Is it really something to worry about if I get paint scratches and stuff? What should I do about them, and are they safe against water etc? Thanks.
You're probably asking the wrong question. When engineers talk about the strength of materials, they usually are referring to "tensile strength". Think about a weight hanging from a solid rod with a 1 sq.in. cross section. How many pounds of load can that rod hold before it breaks apart?

What you probably really want to know is "how likely is a bicycle frame made with carbon fiber to fail vs. one made of aluminum alloy or of some other material?
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Old 09-15-21, 07:05 AM
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Originally Posted by Eric F
The challenge I have with this is that the same frames that are used by World Tour riders are available to consumers. There may be the occasional one-off custom (certainly custom paint, but that's not what we are talking about), but manufacturers are not making special frames for every rider, for just one event. It makes no sense that a frame built from a material with an infinite fatigue life, that can endure the demands of racing for 3 weeks at the highest levels, will have a sudden drop-off of durability and performance shortly afterwards.
Sorry for the delayed reply here. Got tied up yesterday, then zonked early last night.

It's not really a “sudden drop-off of durability and performance”. It’s more like a slow internal degradation due to material fatigue starting on day 1 of use. That slow degradation eventually manifests itself in a crack or break - which I guess could qualify as a “sudden drop-off in durability” if you want to consider it that. Until that happens, performance and strength remain essentially unaffected.

Or, as I've read elsewhere (paraphrasing): "They're great - until they aren't." (smile)

The passages you quoted from commenters here seemingly implying that CF has an infinite life expectancy indicate they appear to have misunderstood the meaning of fatigue limit and have it exactly backwards - or are perhaps misreading the definition. My guess is that they’re confusing a material’s fatigue limit (some sources instead use the term endurance limit) and a material’s fatigue strength.

The definition of a material's fatigue limit is “the maximum stress a material can undergo an infinite number of times without failure.” Thus, if a given material does not have a fatigue limit then repeated stresses - no matter how large or small - will eventually cause that material to fail. In contrast, the term fatigue strength has a very different definition and meaning; it’s defined as the amount of stress at which a failure can be expected to occur after a specified number of repeated stress cycles. Unfortunately, the terms are similar enough that it would be easy for someone to confuse the two, even though they refer to two different concepts entirely..

https://www.merriam-webster.com/dict...atigue%20limit

https://material-properties.org/what...th-definition/

https://en.wikipedia.org/wiki/Fatigue_limit

https://extrudesign.com/fatigue-limi...durance-limit/

https://fractory.com/material-fatigu...#Fatigue_Limit

The last source above uses endurance limit in place of fatigue limit, and defines fatigue limit slightly differently (e.g., in terms of a specific but very large number of cycles vice an infinite number of cycles). I wish everyone would use those definitions, as I personally think they're a bit more understandable as well as being more precise. But that usage seems to be less common.

Again, for emphasis: any material without a fatigue limit (as the term is generally used) will eventually fail after it has been repeatedly stressed enough times. That's true regardless of the magnitude of those stresses – and pretty much everything you do while riding causes cyclic stresses in a bike frame. Larger stresses will cause the material to fail with fewer repetitions, while smaller stresses will take more repetitions. But a material without a fatigue limit will eventually experience fatigue failure (e.g., it will crack or break). It will just take longer when the repeated stresses are smaller. Exact prediction of precisely how long this will take is not really feasible for a specific item, but it can be predicted statistically from material properties and expected stress levels experienced by the item during use. And a fabrication or material flaw (or a design flaw that concentrates stresses) can grossly shorten the time required, particularly if the flaw happens to be in a high-stress area.

Designers account for this when using materials without a fatigue limit by designing in a large safety factor - generally by using more material and building a structure that is stronger than absolutely necessary, especially if reducing those stresses isn't practicable. In this case, additional material used translates not only into increased strength but also into a longer useful lifespan. Internal stresses (in simple terms, stress is the force experienced divided by the cross-sectional area) are reduced by having more material over which to "spread" the force.

Materials with a fatigue limit (or if you prefer the term, with an endurance limit) behave differently. Absent some type of damage, they appear immune to fatigue failure - provided that all stresses experienced within the structure remain below the material's fatigue limit. (As I noted previously, anything can be damaged if stressed enough.) They thus behave very differently in this regard than materials without a fatigue limit. As a result, a properly designed and constructed structure made from a material with a fatigue limit theoretically has an infinite lifetime provided it is never over-stressed. Material or fabrication flaws, or poor design that concentrates stress in a particular area, can of course reduce the overall force on the structure required to break the structure at that point; and any type of damage (including corrosion) can also obviously change the structure’s lifetime.

AL and CF composites are generally regarded as not having a fatigue limit per the above standard definitions, while in contrast steel and titanium indeed appear to have fatigue limits. (I say "appear to" as it's somewhat problematic to verify definitively that steel and titanium have such a limit via stressing a test sample an infinite number of times at a level below the material’s apparent fatigue limit.) Regardless, in practice all four can be used to make excellent and long-lasting structures - including bike frames. The designer simply has to take the varying properties of each into account and design accordingly.

Bottom line: absent damage or a design/fabrication/materials flaw, a properly-designed AL or CF frame will IMO likely have a longer useful lifetime than its rider, even if it won’t last forever. That’s because I’d I’m reasonably certain that they’re designed to be far stronger than absolutely necessary in order to extend their useful lifetimes to account for the absence of a fatigue limit – if for no other reason than legal liability and manufacturer reputation. Precisely how long will it be safe? Dunno. But I wouldn’t sweat it overmuch.

However, I’d still look over a CF or AL frame or fork carefully on a regular basis – which reminds me, I need to do that to mine this coming weekend. And if I had a thousand-year life expectancy, I might be hesitant to ride an AL or CF frame or fork made today 500 years or so in the future without knowing a helluva lot of details about its design and the quality of its fabrication and materials - unless I could verify that it was NOS. (smile)

Last edited by Hondo6; 09-15-21 at 08:45 AM. Reason: Correct typos and wording changes.
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Old 09-15-21, 09:18 AM
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Originally Posted by Eric F
What does this have to do with CF bicycle frames?
Many claim that if planes are made with CF, it must be good for bicycles.
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Old 09-15-21, 09:19 AM
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Originally Posted by Steve B.
American Airlines flight 587 had a failure of the carbon fiber vertical stabilizer that was not an actual failure of the material, but the bolts and assembly that held the tail to the fuselage. The failure was a result of Airbus's lack of movement limiting in the steerable section of the tail that subsequently caused the stabilizer to separate from the plane The co-pilot, having encountered severs vortices from a flight that had taken off before them, over corrected with the vertical stabilizer mechanism (itself a result of improper training), and caused the rudder mechanism to exceed design load. Likely would have happened if the tail was aluminum. Nobody ever blamed the use of carbon fiber.
Always blame the pilot.
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Old 09-15-21, 09:31 AM
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Originally Posted by rydabent
Always blame the pilot.
I wasn't doing that. I stated improper training, which was one reason for the disaster, the training did not correctly teach the pilots how to not overuse the pedals to apply the correct amount of force so as to not cause the aircraft to lose directional flight. The NTSB identified this as a problem with both the information Airbus provided to American as well as the training American provided to the pilots. My take was a bad design on Airbus to allow that amount of rudder control where it would exceed the design strength.
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Old 09-15-21, 09:50 AM
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Originally Posted by rydabent
Many claim that if planes are made with CF, it must be good for bicycles.
At this point, it's not even about "if it's good for planes then it must be good for bikes". CF composite material has proven itself over multiple decades to be strong, durable, and lightweight, with excellent properties for making lots of products. Bike frames, forks, cranks, stems, seatposts, handlebars, etc. are some of them. So are many other aircraft, auto, aerospace, sports, medical, etc. applications. It's not a mystery material.
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Old 09-17-21, 09:21 AM
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Originally Posted by Steve B.
I wasn't doing that. I stated improper training, which was one reason for the disaster, the training did not correctly teach the pilots how to not overuse the pedals to apply the correct amount of force so as to not cause the aircraft to lose directional flight. The NTSB identified this as a problem with both the information Airbus provided to American as well as the training American provided to the pilots. My take was a bad design on Airbus to allow that amount of rudder control where it would exceed the design strength.
Of course that is BS. A pilot will move the controls to get the response he or she wants. Do you really think that a pilot will say to himself ----gee that is all the rudder I dare to put in------------In the case of the tail breaking off the Airbus airplanes is a combination of CF design not being strong enough, and the fly by wire being programed wrong. On the very light weight Cessna 150s I learned to fly in, in cross wind landings often I used full rudder to keep the plane straight on landing.
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Old 09-17-21, 09:24 AM
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Originally Posted by Eric F
At this point, it's not even about "if it's good for planes then it must be good for bikes". CF composite material has proven itself over multiple decades to be strong, durable, and lightweight, with excellent properties for making lots of products. Bike frames, forks, cranks, stems, seatposts, handlebars, etc. are some of them. So are many other aircraft, auto, aerospace, sports, medical, etc. applications. It's not a mystery material.
The crashes of several Airbus airplanes made of CF, and the crash of an F-117 at an airshow says the CF IS NOT the wonder material that many think it is. Then in cycling how about the many crashes of bike with front CF forks that suddenly shattered, putting the rider on the ground????
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Old 09-17-21, 10:10 AM
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Originally Posted by rydabent
Of course that is BS. A pilot will move the controls to get the response he or she wants. Do you really think that a pilot will say to himself ----gee that is all the rudder I dare to put in------------In the case of the tail breaking off the Airbus airplanes is a combination of CF design not being strong enough, and the fly by wire being programed wrong. On the very light weight Cessna 150s I learned to fly in, in cross wind landings often I used full rudder to keep the plane straight on landing.
It appears that the NTSB disagrees. Quoted from the Executive Summary of the NTSB's report on the accident, which is readily available in PDF format on the Internet:

The National Transportation Safety Board determines that the probable cause of this accident was the in-flight separation of the vertical stabilizer as a result of the loads beyond ultimate design that were created by the first officer’s unnecessary and excessive rudder pedal inputs. Contributing to these rudder pedal inputs were characteristics of the Airbus A300-600 rudder system design and elements of the American Airlines Advanced Aircraft Maneuvering Program.
The "Advanced Aircraft Maneuvering Program" referenced here appears to be at least part of AA's pilot training curriculum. And in another part of the report, it goes on to indicate that the first officer had a history of being aggressive (a previous aircraft Captain who had flown with the individual as First Officer had referred to it as being "very aggressive") in the use of rudder controls during a similar previous incident while flying another type of aircraft. The Captain of that flight also indicated he regarded the Flight Officer's actions as excessive in that case; however, also indicated he felt that this behavior was "our of character". (This previous behavior on the part of AA 587's late Flight Officer is discussed on p. 12-13 of the report.) The Advanced Aircraft Maneuvering Program and its issues are discussed in detail later in the report.

I have no axe to grind here, and I'm not a pilot. But yeah - per the NTSB, there apparently were issues with the Flight Officer's behavior that contributed to the crash. There also appear to have been issues with the training he received and with the aircraft's rudder system design as well.

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Old 09-17-21, 10:14 AM
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Originally Posted by rydabent
The crashes of several Airbus airplanes made of CF, and the crash of an F-117 at an airshow says the CF IS NOT the wonder material that many think it is. Then in cycling how about the many crashes of bike with front CF forks that suddenly shattered, putting the rider on the ground????
I'm not familiar with all the Airbus incidents you're referring to, but the one discussed above was not a CF material failure. The F-117 airshow incident was determined to be a technician error where over 10% of the fasteners for the wing support structure were not installed. This was also not a CF material failure.

Now, tell me about how bikes made from metals have never failed. Planes, too.
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Old 09-17-21, 10:34 AM
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Seem silly to even be talking about planes in a bicycle forum. There have been many planes with steel frame structures that failed and crashed for various reasons as have aluminum structures in planes. CF isn't any more prone to failure when correctly used and designed as any other material.

Back when aluminum bikes came on the scene there where plenty of head tube failures and fork failures. Don't see any today questioning how strong aluminum is.
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