I read that those Fibreglass reinforced nylon soles go soft over time or repetitive uses. Does Carbon sole shoes go soft over time too?
Does carbon shoes go soft over time?
machoman
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The CF will not, at least not for an eternity. However, depending on the shoe, the plastics used to make the CF heat moldable can, eventually, get more pliable than new. It depends on the shoe. If you have a custom molded shoe it really won't get more pliable for a long time because it is a higher % CF. But in any case, they will hold their form and stiffness for many years.
So, here is how these things work - Carbon fiber threads have a very high modulus of elasticity. That means they don't stretch very much. They are also fairly strong, but more importantly, they have a high tensile strength to weight ratio. So by themselves, they have some nice properties. However, to make them useful, you need to tie them together so that the tensile strength and modulus on one fiber can work against the tensile strength and modulus of the others. That is what the epoxy does. It provides a sheer tie among the fibers.
Over time, the fibers do not change or soften unless they break. When or if they break you will know it. Fortunately, Carbon fiber doesn't fatigue like a metal, so they will only break if they are overstressed or cut or abraded somehow.
Epoxy is a highly crosslinked polymer. It is entirely possible for the epoxy (plastic) portion of the Carbon fiber product to degrade over time. If that happens one or more changes can occur. The epoxy can separate from the fibers (adhesive failure), it can break internally (cohesive failure) or it can just become more compliant as the weaker bonds in the crosslinking break. That can cause the sheer tie to have a lower modulus and the item behave "softer."
Adhesive or cohesive failures happen when the strength of particular bonds are less that the stress they encounter. So things go south quickly when they do. It also would leave visible evidence (delamination, tears in the object.) Temperature extremes, especially cold, have a habit of changing the stresses in these things and epoxy tends to get stiffer, but ofter weaker in cold, softer and weaker in hot. The good news is that the last kind of issue is pretty uncommon in normal use - unless you are irradiating or putting your shoes in a high temperature oven, or dousing them with Acetone or another organic solvent, you aren't going to be breaking down the polymer chains very quickly.
By the way, I believe what is happening in the fiberglass reinforced Nylon shoes is that the Nylon is fatiguing. I could be wrong there, but that is what it sounds like. Nylon fatigues pretty readily, whereas Carbon fibers do not. In the end, I wouldn't worry about softening the CF stiffeners in your shoes. They will probably outlast every other part of the shoes by a long stretch.
Over time, the fibers do not change or soften unless they break. When or if they break you will know it. Fortunately, Carbon fiber doesn't fatigue like a metal, so they will only break if they are overstressed or cut or abraded somehow.
Epoxy is a highly crosslinked polymer. It is entirely possible for the epoxy (plastic) portion of the Carbon fiber product to degrade over time. If that happens one or more changes can occur. The epoxy can separate from the fibers (adhesive failure), it can break internally (cohesive failure) or it can just become more compliant as the weaker bonds in the crosslinking break. That can cause the sheer tie to have a lower modulus and the item behave "softer."
Adhesive or cohesive failures happen when the strength of particular bonds are less that the stress they encounter. So things go south quickly when they do. It also would leave visible evidence (delamination, tears in the object.) Temperature extremes, especially cold, have a habit of changing the stresses in these things and epoxy tends to get stiffer, but ofter weaker in cold, softer and weaker in hot. The good news is that the last kind of issue is pretty uncommon in normal use - unless you are irradiating or putting your shoes in a high temperature oven, or dousing them with Acetone or another organic solvent, you aren't going to be breaking down the polymer chains very quickly.
By the way, I believe what is happening in the fiberglass reinforced Nylon shoes is that the Nylon is fatiguing. I could be wrong there, but that is what it sounds like. Nylon fatigues pretty readily, whereas Carbon fibers do not. In the end, I wouldn't worry about softening the CF stiffeners in your shoes. They will probably outlast every other part of the shoes by a long stretch.
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No.....
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I had the same Nike Hautacam shoes for eight years, and the carbon fiber soles never flexed.
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What a great reply! Thanks! So, how does a "CF" shoe become "fully heat moldable" per advertisers claims? Is the degree of "moldability" effecting the longevity of the shoe? It's one thing to lay up the strands and make a frame, but it's quite another to lay them over a model (or custom) last and make a shoe that is moldable at 180 degrees? The principles are the same, CF is CF, Toray is Toray... What is happening in the manufacturing that makes the shoe so different? Does that impact performance qualities? Durability? Stiffness? Stiffness over time?
I bought two pair of shimano cf soled shoes 5.5 years ago, because I got a screaming deal on them and they fit my foot so well. I rode one pair exclusively for the first 4.5 years and then decided to break out the new shoes to see how they compared to the old ones. Please note that these are the same model, same size, and same cleat position. The old shoes are noticeably flexier than the new ones. I do stand and stomp pretty hard damn nearly every day, 230 days this year so far, in the foothills west of Denver, but I only weigh 160 lbs. Mine is an apples to apples comparison, so unless someone has done a similar comparison, I would take it with a rather small grain of salt.
I do not have first hand knowledge of these shoes, but I do know about what is used in the aerospace industry (or most anywhere else where CF is used to make piece parts.) In the actual manufacturing process of the items the CF and epoxy comes in the form of "pre-preg", or pre-impregnated CF "cloth". This stuff comes in rolls and in a wide variety of fibers, weaves (or just straight, or "uni", for unidirectional) of the fibers, and epoxies. Now, we normally think of epoxy as either being the runny stuff in two parts that you have to keep apart from each other, or cured. But in pre-preg it is in an intermediate form, known a B-stage epoxy. The stuff I've worked with needs to be kept in the freezer to preserve its properties until it is laid up, typically in a mold, and then put into an autoclave where heat and pressure combine to turn this rather innocuous cloth into things you can make jet engine or spacecraft components from.
However, there is one really cool property that I think is coming into play here. When we make composites we sometimes want to combine components, already cured components, into bigger assemblies. And that's why I know that you can soften cured pieces by subjecting them to higher temperatures than at which they were initially cured. That is because curing is the process of breaking loose bonds and allowing other, stronger bonds to form to make more and more tightly cross linked polymer chains. Normally, that means you want to cure the piece parts at say 350°F, and then, since you don't want them to soften, the cure for the bonding them together part is done with new pre-preg that cures at a lower temperature, say 250°F. That is done specifically so that you don't soften, and potentially deform, the piece parts.
This is where my experience ends in this area pretty much, but what I take from this is that if you wanted to intentionally deform your parts you would cure them, or partially cure them, at a very low temperature. Just high enough to make them relatively stable. Then, you'd figure out how to heat them while applying a deforming, or molding, force. So I expect that the heat moldable part is partially cured, either in an autoclave or at least under vacuum (because you need to get the air out and let the epoxy flow everywhere while getting the fibers nice and tight together) and then fully cured when the higher heat is applied during the molding part.
I hope that makes sense.
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If it is a heat moldable shoe, this is the likely evolution. It will vary dramatically by model, wear, weight and usage. The degree a shoe loosens up and the slow rate at which it happens may well be insignificant to the rider.
Oh Jesssssssssssssssss
You are such and engineer.
Why use 5 words when 5000 describe it exactly.
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YMMV. The CF will degrade to some small extent, but not for a long time, so long as it is well built. Old frames don't stretch. Who knows what materials at what percentages (and where) have been used to make those shoes.
Insignificant to the rider until you try out a new pair.......like all things in life nothing lasts forever...not even Carbon, not even true love. Sad........
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Hockey skates today are heat moldable. Hockey skates started using carbon fiber sole in mid 1990s, and started being heat moldable around year 2000, but not for the carbon fiber sole, it's for the boots, to shorten the break-in period of new hockey boots.
I believe the heat moldable bike shoes you're talking about, is refering to the upper part of the shoes, not the sole.
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Yes. Of course. The carbon fiber has degraded. Like bicycle frames, it is getting softer as you use it. It will be a noodle soon. CF gets mushy every 3-4 years regardless of the other materials used or the nature of the lay up. By this logic, a 4 year old CF frame is completely unsafe. OK...
So you're going with no then?
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Nylon is not fatiguing. In fact firbreglass has a higher strength to weight ratio than carbon fibre. So in many composites fibreglass will be used to augment as a filler material. This gives a measure of strength and durability to the composite material.
If you are finding firbreglass getting soft it may well just be a deterioration of some of the composition materals. You can't put a blanket statement on it either way, depends very much on the quality of materials and workmanship of the product.
If you are finding firbreglass getting soft it may well just be a deterioration of some of the composition materals. You can't put a blanket statement on it either way, depends very much on the quality of materials and workmanship of the product.
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