Derby cycle IMPULSE 2.0 - Page 30

30 Bicycle Owner’s Manual
Carbon ber composites are typically a strong, light
ber in a matrix of plastic, molded to form a shape.
Carbon composites are light relative to metals. Steel
weighs 7.8 grams/cm
3
(grams per cubic centimeter),
titanium 4.5 grams/cm
3
, aluminum 2.75 grams/cm
3
.
Contrast these numbers with carbon ber composite at
1.45 grams/cm
3
.
The composites with the best strength-to-weight ratios
are made of carbon ber in a matrix of epoxy plastic. The
epoxy matrix bonds the carbon bers together, transfers
load to other bers, and provides a smooth outer surface.
The carbon bers are the “skeleton” that carries the load.
Why Are Composites Used?
Unlike metals, which have uniform properties in all
directions (engineers call this isotropic), carbon bers
can be placed in specic orientations to optimize the
structure for particular loads. The choice of where to place
the carbon bers gives engineers a powerl tool to create
strong, light bicycles. Engineers may also orient bers to
suit other goals such as comfort and vibration damping.
Carbon ber composites are very corrosion resistant,
much more so than most metals.
Think about carbon ber or berglass boats.
Carbon ber materials have a very high strength-to-
weight ratio.
What Are The Limits Of Composites?
Well designed “composite” or carbon ber bicycles and
components have long fatigue lives, usually better than
their metal equivalents.
While fatigue life is an advantage of carbon ber, you
must still regularly inspect your carbon ber ame, fork,
or components.
Carbon ber composites are not ductile. Once a carbon
structure is overloaded, it will not bend; it will break. At
and near the break, there will be rough, sharp edges and
maybe delamination of carbon ber or carbon ber fabric
layers. There will be no bending, buckling, or stretching.
If You Hit Something Or Have A Crash, What Can You
Expect From Your Carbon Fiber Bike?
WARNING: Defects and cracks in composites might
appear without being visible! If you have had a
crash, ear unusual noises or feel a dierence while
riding, let your dealer check the bike or the part. Don`t
continue the ride before having the bike or part beeing
checked!
Let’s say you hit a curb, ditch, rock, car, other cyclist or
other object. At any speed above a fast walk, your body
will continue to move forward, the momentum carrying
you over the ont of the bike. You cannot and will not stay
on the bike and what happens to the ame, fork and other
In most cases a fatigue crack is not a defect. It is a
sign that the part has been worn out, a sign the part has
reached the end of its usel life. When your car tires wear
down to the point that the tread bars are contacting the
road, those tires are not defective. Those tires are worn
out and the tread bar says “time for replacement.” When a
metal part shows a fatigue crack, it is worn out. The crack
says “time for replacement.”
Fatigue Is Not A Perfectly Predictable Science
Fatigue is not a perfectly predictable science, but here
are some general factors to help you and your dealer
determine how oen your bicycle should be inspected.
The more you t the “shorten product life” prole, the
more equent your need to inspect. The more you t the
“lengthen product life” prole, the less equent your need
to inspect.
Factors that shorten product life:
 Hard, harsh riding style
 “Hits”, crashes, jumps, other “shots” to the bike
 High mileage
 Higher body weight
 Stronger, more t, more aggressive rider
 Corrosive environment (wet, salt air, winter road
salt, accumulated sweat)
 Presence of abrasive mud, dirt, sand, soil in riding
environment
Factors that lengthen product life:
 Smooth, uid riding style
 No “hits”, crashes, jumps, other “shots” to the
bike
 Low mileage
 Lower body weight
 Less aggressive rider
 Non-corrosive environment (dry, salt-ee air)
 Clean riding environment
WARNING: Do not ride a bicycle or component with
any crack, bulge or dent, even a small one. Riding a
cracked ame, fork or component could lead to complete
failure, with risk of serious injury or death.
B. Understanding composites
All riders must understand a ndamental reality
of composites. Composite materials constructed of
carbon bers are strong and light, but when crashed or
overloaded, carbon bers do not bend, they break.
What Are Composites?
The term “composites” refers to the fact that a part or
parts are made up of dierent components or materials.
You’ve heard the term “carbon ber bike.” This really
means “composite bike.”