To any designer, who uses applied math, strength of materials, physics and some go as far as doing finite element analysis on bicycle frames it is 100% relevant.

If you are not into that, lets agree to disagree.

True, defensive people on both sides of the aisle....some show up to these threads.

When "designers" spec plastic panels for automobiles, they do not use standard ASTM tensile or compression stress-strain data to predict the impact behavior of the panels. They use a Dynatup, high-speed, motor-driven impact testing to predict the impact behavior of the material. It is similar for the impact behavior of a bicycle frame construction material. The graph you showed wouldn't tell anyone squat about how the material would behave if hit by a car. On the other end of the spectrum there is no substitute for constant stress creep testing for the very slow effects. You can speed up getting the creep results by applying time-temperature superposition, but the constant stress test must be run for as long as it takes to get failures. The type of data that you showed would be worthless for either of those purposes.

Not into what, using irrelevant data and trying to dress it up by the complexity of how you apply it? Bad data in, bad results out.

Take note guys, if CF composites are tested only as [MENTION=369016]ColnagoC40[/MENTION] suggests, maybe we do have something to worry about!

OK, I'll bite for more intellectual discussion using strength of materials calculations.

But first where do you have plastic panels on your bike? Plastic, PVC, ABS ? They all have creep properties. Where is this applicable to a bicycle????

Steel, starts creeping at around 800F, so where is your relevancy discussion going with this?

For carbon fiber, creep tests beyond 50 year design life show no risk, what is relevant here?

Wow!!!

It's been a long time, but I believe what you regard as irrelevant is 1st 2nd year college Engineering, in some European schools final grade.

The plastic panels reference was what is known as an analogy. I realize that those who are fewer than 15 years or so removed from SAT testing may not recognize that concept, but I am sure you can find some information about it in the online dictionary.

Furthermore, a so-called carbon fiber bike is, as you should know, entirely constructed of fiber-reinforced plastic. The whole bike is plastic, tubes and lugs, not panels, but that is where the analogy idea comes in. If the most likely stress leading to catastrophic failure is going to be some form of impact, then the construction material and finally the finished product should be tested for resistance to impact. That isn't done on a common Instron tensiometer, and the testing doesn't generate the type of data you showed. Such impact testing data is important for any material, but particularly a plastic either neat or as a composite. Do you honestly think that Reynolds didn't test the impact characteristics of each and every new steel alloy it introduced in tubing for over the years?

Now about creep. That is the first thing I thought of when I saw the sheared off steerer tube photos posted earlier in this thread. You have a cylinder of CF composite under tension (aka preload) for a very long period of time. The failure may not have been due to creep, but if I were that fork manufacturer, I surely would want verification of that. And that evidence won't be found in the standard stress-strain plot.

As far as my thinking that the first couple of years of college engineering education is irrelevant, nothing could be further from the truth. Knowing about these physical phenomena and being able to test and describe them numerically is extremely important, but so is knowing when a certain type of data is applicable and when it is not. The data you showed certainly had to have been generated. It is fundamental to the understanding of the utility of CF composites relative to other materials. But you have to know when you need something more than such basics.

I must have been late to notices this thread or its moving very quickly, either way, if carbon fiber is so infinitely strong and ultimately durable, Why aren't touring bikes made from carbon fiber?

It's not because there isn't enough of a market for them, there are many people who bicycle tour and fly to their destination. Steel bikes are very heavy and subject to luggage weight and additional fees at the airport however steel is the number one material for touring bikes. Carbon fiber touring bikes could be mass produced just as easily as a carbon road/mountain bikes. Even if they came at a premium price there would be a market for them, kind of like all the social road bike riders that don't race and insist on riding Dura Ace/Record equipped bikes with carbon fiber racing wheels regardless of how unnecessary this level of equipment is for their needs.

Surely if carbon was as superior as claimed the all other materials would be redundant and we wouldn't bother building out of titanium or any other material.

The fact is that every material has its limitation, its positives and its negatives. Carbon fiber is very likely to implode into tiny splinter when its maximum sheer strength is exceeded. I have witnessed this hundreds of times while participating at drag racing events. Carbon fiber is regularly used in down force wings on top fuel dragsters and the bodies of nitro funny cars. After bouts of sever tire shake some carbon parts will expire in spectacular fashion and splinter into many sharp little splinters. Evidence that carbon is not infallible. While I accept that this an extreme example, it illustrates that carbon could break similar to the description and if our carbon bikes are exposed to forces that exceed their maximum sheer forces they are likely to fracture as well.

In the race for bikes to become lighter and lighter, the consequence is less and less material being user and ultimately/eventually this means weaker and weaker bikes. Top level racing teams and manufactures who perform their own in house research and development don't really care about how long their bikes will last for, they are motivated by two things; putting their riders onto the podium and selling lots of bikes. Super light weight bikes are considered for the short term as there is always the next best technology always being developed and they don't want to miss out on the action. Consumers who believe that their current state of the art carbon machine will last for an incredible time are experiencing a misconception of their bikes actual purpose. e.g. How many 10 year old cutting edge carbon bikes are still cutting edge? And more importantly, how many have been retired due to stress fractures?

Hundreds of times?

I would assume that getting them ON the podium would mean that they care about getting them TO the podium, along with a few other key performance parameters, no?

the question is not "is it safe", because that applies to everything. the question is "do you have good insurance" ande "does the vertically compliant and horizontally stiff ride of a carbon fiber bike give you a reason to risk your health and spend thousands of more dollars to purchase it."

This is a gross oversimplification. Carbon is the right tool for some jobs, not for others.

Ah, now we are getting somewhere. Thanks for the recent SAT testing confirmation, that explains the level of experience.

First I beg to disagree with calling carbon fiber plastic, the epoxy resins are not even plastic, further semantics to that extent are not even applicable.

Let me explain: The resin only functions in keeping the fibers together and the UTS is derived from the fibers and their layup, the resin has very little effect on strength. Hence the reason that all current testing at around 85% of UTS shows no creep, with tests designed to accelerate beyond 50 years.

As far as basic strength of materials are concerned, experience teaches us to keep things simple.

So, if I ask a 10 year old if it is important to build a simple tubular frame to withstand a strong rider and light crash, whether it is important that the materials used for the tubes are strong enough, I am pretty sure he/she would say "YES"

If I ask a first year Engineering student the same question, I am 100% sure, the answer will be "YES"

If I ask the student how he would know how strong the materials are, I would expect him to say he would find the Yield Strength and for deflection he would want stress and strain values.

If I ask him where he would get that, I would expect him to pull a curve, exactly as the graph I posted.

If you don't get that, Sir, I really do not have the patience to continue this discussion.

As far as your impact failures are concerned, if you hit a steel pole with your frame, that would be impact. If you crash on the pavement, it would not necessarily be impact and simple calculations will yield reasonable expectations. Never the less, some of us understand that volume, modulus of elasticity, distribution of forces, and yield strength affect the impact strength of a material. Hence the graphs posted still gives a good idea of impact strength from one material compared to another, should they have a similar base. Experience will also tell us the the perfectly straight line graph for carbon fiber, shows a non-ductile material which will not be great in terms of impact resistance.

Comparing a simple tubular frame construction in calculation to plastic vehicle destruction as per your analogy is absurd.

From here flame as you wish, my patience is out and I am gone, no further replies.

Just like touch interfaces.

And some of us understand to use the "Paste as plain text" option so that the different font doesn't make it quite so obvious when we copy/paste from wikipedia.

Utter BS.

You talk as if this information is hard to find or somehow mysterious. It isn't. They data is widely available with a simple google search.

More mindless hysteria.

1. Wrong tool for the job.

2. No rack/fender mounts.

3. The market is too small for the capitol investment by those who make carbon.

Don't you sell carbon wheels, bob?

I am glad to learn that information about carbon fiber composite creep. That's valuable information, which incidentally you have because someone did the specialized testing. I'm also glad you can intuit complex material properties from minimal data so well. I just hope you are not involved in the design or validation of any product I ever need to use. In 30+ years of material related research and development, you are the first person I have ever encountered who maintained that less data is better than more data.

Just for completeness, rest assured that cured epoxy resin is a thermoset plastic. Why would you even argue with that?

Incorrect.

The early Vitus and Look failures were not of the CARBON TUBES. The failure were at the BONDING of the carbon to the alloy lugs.

Again, it was not a CARBON FAILURE, it was a BONDING FAILURE.

In the early days if carbon was so bad it would have been nixed as a material not unlike Magnesium was for rims (I know one from maker using this material). If carbon didn't show and demonstrate such promise and entire industry wouldn't have invested MILLIONS of dollars to retool and move in that direction.

Yes.

The article is a puff peice without a single varifiable fact. His statement is meaningless.

The article, and his staement, is directed at those who simply have no idea how many bikes a real pro goes through in a season (regardless of material). They would be equally amazed at how many tires, waterbottles, wheels, uniforms and calories are consumed by a pro in a season. Why? Because all of those numbers are well beyond what a layman could even possible guess at.

Also, if I recall correctly (this article has ben brought up before), he isn't working with UCI pros. He was working with a wide range of riders including amateur racers who have no useful input into the discussion about professional riders.

...I have altered my original posting in order to accommodate your failing vision.

A question for you, signeur. If the OP's frame fails because of the bonding, lets say at the down tube/headtube junction, will it hurt any less ?


Finally, you, of all the people who post here ought to have access to a testing service for CF bicycle frames and components. Link please ?

Come to think of it, I'm 55 year old carbon. Another 20 and I should probably worry about crashing...

Carbon doesn't rust.

I think Neil Young said it best....Rust never sleeps.

How does a bonding failure have anything to do with the properties of carbon and it's suitability as a frame material? It doesn't.

Do your own google work. Links to test and videos have been posted on this forum and others countless times. They didn't sway your entrenched position now and I doubt seeing two or three more would do it today.

Also, I wouldn't post private test results. They are not my property to share. There us a ton of material in the public domain. Have at it.

Yes (rims really).

We also work in (and off the top of my head and in no particular order): Injected plastic, extruded 6000 series alloys, machined 6000 and 7000 series alloys, stamped alloys, drawn stainless, ceramic, leather, sythetic leather, nylon, PU plastic, cr-mo steel and I know I am missing some.

In fact, the project I am working on now (in the OE) is a lugged steel frame using a more traditional geo but with an updated hdst design and carbon fork.