Excellent Information on Carbon in Bikes

Engineer Steve A has begun to address the questions I have raised about inspection of carbon bikes and parts. This post on his blog, DFW Point-to-Point discusses the issue of how to assess potential risk. Unfortunately, for those without ultrasound, x-ray or other imaging equipment it still comes down to what you see and what you suspect. It's still good to get a briefing from someone outside the bike industry, who has considerable experience with the material. I look forward to more.

Customer Methodology 101

1: Call first thing in the morning to extract a promise that a certain job can be done by closing time.

2: Don't bring in the object in question until lunch time or later.

Advanced play:

3: Don't pick up the item for a week or more.

4: Bitch about the price.

Trying to be a responsible mechanic...

The lowly bicycle mechanic has fallen under a vast load of technical crap in the past couple of decades.

First came the frantic "innovation" of the mountain bike era. As the avalanche of technology crushed the enthusiasm out of most casual recreational participants, the industry grabbed at the straw of advanced materials to try to stimulate addiction among a clientele with plenty of disposable income. And so, carbon fiber became commonplace. It mated well with the resurgence of road biking, as the surviving cyclists moved toward smoother rides and fewer mechanical problems.

Carbon fiber brings its own special issues which require dire warnings to the consumer. Blah blah blah, risk of serious injury or death, etc. The owner's manual and any supplemental bulletins always say, "If the bike suffers any impact, have it inspected by your Authorized Dealer."

Since the only qualification to be an authorized dealer is a credit rating acceptable to the accounts receivable department at Wonderbike, Inc., just exactly what makes the poor dingus at the Greasy Hub Bike Emporium more qualified than anyone else to say with any certainty that the expensive part under scrutiny is actually safe?

The warning sheet that came with a Specialized I just assembled says, "Damage to composite is difficult to visually identify." So I went looking --not for the first time-- for more advanced and reliable methods. With all the carbon fiber used in aerospace and other truly serious applications, someone must have better advice than, "Examine it carefully. If you have a bad feeling about it, throw it away and buy a new one."

Here is the result of about an hour trolling on the Internet for articles related to "inspection carbon fiber impact damage:"

From IEEEXPLORE

A high critical temperature SQUID magnetometer has been successfully employed in the evaluation of the behavior of multi-ply carbon fibers reinforced composite panels for aeronautical applications under low-velocity impacts.

Measurements of the induced magnetic field have been carried out above specimen damaged with energy impact from 1 to 40 J. A quasi-linear behavior in two different regimes between the SQUID's response and the energy of the impact has been found. This suggests a correspondence to the detection of intrinsically different damage that occurs in the laminates at different energies

I wants me a SQUID magnetometer, just so I can say I have one.

"Is my fork okay?"

"Quickly! To the SQUID magnetometer!"



From POLIMEROS:

Polímeros
version ISSN 0104-1428
Abstract

TARPANI, José R. et al. Thermographic inspection of impact damage in carbon fiber-reinforcing polymer matrix laminates. Polímeros [online]. 2009, vol.19, n.4, pp. 318-328. ISSN 0104-1428. doi: 10.1590/S0104-14282009000400012.

Continuous carbon fiber reinforced thermoset and thermoplastic composite laminates were exposed to single transversal impact with different energy levels. The damages impinged to the structural materials were evaluated by active infrared thermography in the transmission mode. In general, the thermoplastic laminate thermograms showed clearer damage indications than those from the thermosetting composite. The convective heating of the samples by controlled hot air flow was more efficient than via irradiation using a filament lamp. It was also observed that longer heating times improved the damage visualization. The positioning of the specimen's impacted face regarding the infrared camera and the heating source did not affect the thermo-imaging of thermosetting specimens, whereas it substantially influenced the thermograms of thermoplastic laminates. The results obtained allow concluding that infrared thermography is a simple, robust and trustworthy methodology for detecting impact damages as slight as 5 J in carbon fiber composite laminates.

[Impact damage of carbon fiber polymer–matrix composites, studied by electrical resistance measurement
Purchase the full-text article

References and further reading may be available for this article. To view references and further reading you must
purchase this article.] Dealer tax and title not included. Some restrictions apply.

Maybe infrared thermography is the affordable solution. I haven't priced the equipment yet.

AND AS CITED:

Shoukai Wanga, D.D.L. Chunga, Corresponding Author Contact Information, E-mail The Corresponding Author and Jaycee

H. Chungb

aComposite Materials Research Laboratory, University at Buffalo, State University of New York, Buffalo, NY 14260-

4400, USA

bGlobal Contour Ltd, 1145 Ridge Road West, Rockwall, TX 75087, USA
Received 24 June 2004;
revised 20 February 2005;
accepted 24 February 2005.
Available online 13 May 2005.

Abstract

Drop impact damage of continuous carbon fiber epoxy–matrix composite laminates, was studied by electrical resistance measurement, which was shown to be more sensitive than the ultrasonic method. The oblique resistance at an angle between the longitudinal and through-thickness directions was more effective than the surface longitudinal resistance in indicating damage, particularly interior damage. The oblique resistance values from longitudinal segments of a specimen were not additive, but the surface resistance values were.

In the case of a unidirectional composite, electrical contacts at 45° from the longitudinal direction in the plane of the laminate were more effective than those at 90°. Even minor damage associated with negligible indentation was sensed. The spatial distribution of damage was also studied.

AND....

Shoukai Wang1, Daojun Wang1, D. D. L. Chung1 Contact Information and Jaycee H. Chung2
(1) Composite Materials Research Laboratory, University at Buffalo, State University of New York, Buffalo, NY

14260-4400, USA
(2) Global Contour Ltd., 1145 Ridge Road West, Rockwall, TX, 75087

Received: 7 April 2005 Accepted: 24 June 2005 Published online: 3 March 2006
Abstract The method of sensing impact damage in carbon fiber polymer-matrix structural composite by DC electrical resistance measurement was evaluated by measuring the resistance of the top surface (surface receiving impact). The resistance obtained by using the four-probe method is a more sensitive, more precise (less data scatter) and more accurate indicator of composite damage than that obtained by using the two-probe method. The data scatter is low for both four-probe and two-probe resistances for impact energy up to 5 J, but it is lower for the four-probe resistance than the two-probe resistance. The data scatter increases with damage. It is attributed to electrical contact degradation. The four-probe resistance of the 8-lamina composite increases upon impact, such that the fractional increase diminishes as the distance from the point of impact increases. The four-probe resistance of the 24-lamina composite increases upon impact for the specimen segment containing the point of impact, but decreases slightly upon impact for the segments within about 20 mm from the point of impact. The two-probe resistance has less tendency to decrease upon impact than the four-probe resistance.

Hmmm. If you really want to know, check the four-probe resistance.

Until we upgrade our testing equipment, all you can do is look for dings or cracks, listen for scary noises, wear a mouth guard, and if something makes you nervous, replace it, no matter how much it costs. The bike industry thanks you for your business. That noise, that gouge? They're probably nothing.

You and me and the Culture of Speed

Cycling advocates use the term "Culture of Speed" to describe the moto-centric mentality that breeds contempt, hostility or neglect toward the needs of non-motorized travelers on the public streets and highways we all try to share.

Truly addicted drivers will be as rough on each other as on the hapless bicyclist or pedestrian who happens to interrupt their flight. In fact, it's probably worse between motorists, because they tend to be going closer to the same speed, in vehicles that are harder to overtake because they fill more of the lane.

Two things got me into bike commuting 30 years ago. One was exercise. I knew I needed it, and forcing myself to do it to get around seemed like an excellent plan. Second, in the congested streets of Annapolis, I could get around faster than a driver and I could park much more easily. So in pursuit of speed, I adopted a human-powered vehicle.

As my commute shifted from one part of town to another I used roads on which I did not go faster than the cars. The other advantages remained.

Here in New Hampshire, I ride most of the distance to work on a highway. The trip definitely takes less time in a car. The little town of Wolfeboro, however, is very congested in the summer, and parking is scarce. I can't claim better speed than the cars, but I do enjoy a better mental and emotional flow.

Humans are content when their flow rate matches their expectation. Bicyclists enjoy this much more often than motorists do. Too many things can and should hinder the flow of motor vehicles. Motor vehicles are large, hard and heavy. They can do a lot of damage to themselves and their surroundings when they follow an unplanned trajectory. But because they have the potential to go much faster than is often advisable, their pilots live in a near-constant state of discontentment.

Because cyclists have done the calculation and decided to accept a lower overall speed range, we are happier in our culture of speed than the drivers of powerful vehicles held in check by what can often seem like artificial limitations.

People drive because they want to get where they're going. Motorized transportation allowed people to pack their schedule with more events. That capability became the norm. Yes, a power-assisted lifestyle has many undesired, unintended consequences. But it's very easy to descend into the addiction.

We who are our own engines purchase equipment and learn techniques to make our rational choice work. Some of us have to shower when we get to work. Often we have to give up events or activities if we can't get ourselves from here to there in time and in acceptable condition. Or we make special arrangements to work around what someone else might accomplish by driving a car at a faster speed than we can pedal, to arrive fresh and ready, not breathless and sweaty.

Many people who use bikes as transportation also use motor vehicles. We just use them less.

I'm really looking forward to using mine less in a few weeks. I hope the weather cooperates with the increasing daylight to allow an early transition to bike use. The winter certainly has been a bust for alternative training and fitness activities. My main worry is that this has been my worst winter in decades for keeping fit. Music is partly to blame, as I put time into instrument practice that I formerly would have put into various forms of indoor exercise when the outdoor conditions went bust. I confess it is all too easy to talk me out of using a Nordic Track, a bike trainer or even the weight bench anymore. But even before my late-life grab at musicality I was trying to put more time in at the drawing table. I really need my commute, for all the reasons that made sense 30 years ago. It's so damn convenient to stick that ride between me and the paycheck in the morning, and me and supper in the evening.

Worse yet, my brain is shifting to motor mentality. Deprived of the balanced equation between the speed I'm capable of doing and the speed I'm getting to do, I grow irritable. I try to do creative or useful things in the morning and then dash to work in the rocket sled, only to find other people's sleds in the way. I try to get to work early, to get the place set up for the day, only to lose my high ground because some rolling speed bump happens to ooze out of a driveway or a side road just before I get there. At the end of a frustrating day devoid of exercise or creative satisfaction, I want only to get home to the music stand and the drawing board, or maybe just the blog, only to come up on the dim taillights of someone driving inexplicably at 42.17 miles per hour on the highway where 55 is permitted. It's a clear, dry night. They're not slowing for an intrepid cycle commuter. They're just meandering.

I really miss my bike. When I ride it I get home later than I would in a car, even driving behind a meanderer. I'm frequently sore and tired. But at least I got myself there as fast as I could go. I can shower, stretch, eat, relax and think. Sometimes I wish I lived a shorter ride from work, but I never wish to be in the car if I have a choice. I have too much need for my speed.

February: A Lot Like the Middle of Nowhere

Usually I'm working 12 straight days during this part of February. Massachusetts schools take a break during the week following the President's Day holiday. Vast numbers of Massachusettsans flood winter recreation venues. It's like a herd migration.

Winter isn't cooperating. Some vacationers have come up anyway, apparently for the ice skating. A few have even tried the six kilometers of trail we have on life support.

With no work marathon, I'll probably try to go for a ride tomorrow. Then the forecast gets murky. Tuesday could bring enough snow to make a better skiing surface. Or maybe it will just muddle up the outdoor riding. So what season is this?

The stack of firewood in the shed dwindles. The days lengthen. Snow could turn it into winter. Or we could just go on, day after dusty, windy day, salt and sand on frost-heaved pavement, far from spring.

Sunny with cream cheese

Went for another fixed gear ride yesterday under sunny skies, with milder breezes than the day before. I should have chosen the fixie with fenders, because a high around 40 sent meltwater streams across the roadway in places. It wasn't bad. I just hate brining the Traveler's Check.

After I got home I was doing some chores around the yard when I noticed that the snow had the perfect skating and turning surface we refer to as cream cheese. The snowpack was basically firm, with a very cooperative top layer. Too bad I had to move on to other important tasks.

Windblown debris covers the decaying snow. The skiing wouldn't have taken me far. I could see myself hooking a tip on some piece of crap in the beech glades or the logged areas up the back mountain. For the moment it seems wiser to look toward cycling season.

Starts and restarts

My wife's mother died at the end of January. That makes any whinge about lack of riding or skiing opportunities seem unforgivably trivial unless you consider the anti-depressant effects of exercise and the value of positive routines to help overcome the considerable stress of unhappy events.

Indeed, my wife resumed her trainer rides when we returned from the funeral trip. I was the laggard, already in a slump with the destruction of cross-country ski conditions after heavy rain took out most of the trail system a few weeks ago. And I got a headcold on the airplane trip. So the ride I took today was long overdue.

I haven't had this long a break in training since about 1979. Even when I quit racing bikes I still commuted, and I trained for climbing and mountaineering, so I ran, hiked, and followed a regular upper-body conditioning program. Exploring demands fitness.

My wife was a runner for many years. Whenever she needed to jump-start a conditioning program she would run. Unfortunately, the impacts finally caught up with her. She rides the trainer with admirable dedication. She also has discovered the fixed-gear, for when she's inclined to go back out on the roads.

Fixed gear does for me what running did for her. Cross-country skiing is more complete exercise, but requires certain conditions. Ski machines are mentally torturous. When I need to blast the lethargy and get moving, the fixed gear provides the same continuous effort that running requires (no coasting), without the impact.

I've read a little about chi running. It seems intriguing. When I ran, I did not suffer injuries, but I never ran for more than a few months at a time. I would always resume one of my preferred activities when I got the chance. I'm a bike guy. From the little I've skimmed about chi running, it sounds like a way to promote a light-footed stride that I may have possessed naturally. I remember the beginning of every summer in childhood, when all the neighborhood kids would recondition their feet to go barefoot. I ran all over the place with no shoes, once my feet were toughened up. The barefoot stride apparently trains you not to strike heavily on the heel. I do remember padding like an animal when running barefoot.

I would have to run along the roads around here. Some people stud an old pair of running shoes and use the snow machine trails. It's so much easier to break out the fixed gear and knock off ten or fifteen miles.

This is February. It could be the beginning of riding season. It wouldn't be the first time. It needs to be something.

The big snow in the Middle Atlantic region of the US makes my Mobile Groomer idea look pretty good. Big cargo aircraft would transport grooming equipment to create cross-country ski trail networks wherever heavy snow had just fallen. The mobile units would stay as long as they were needed. They could also bring mobile rental and retail facilities to bring the Nordic area to the snow rather than sit in one place and hope the weather comes to them. There are parks and golf courses in many places that see snowy winters on an irregular basis. No one would invest in a permanent facility there, but some sort of broad-based investment system might support mobile facilities.

None of this helps me in snow-deprived New England. I still have to do my rides on the sandy, dusty roads with a cold wind pushing me around. But it would help me, knowing that the bounty of snow somewhere else wasn't going completely to waste.