University Project: Material and Process Selection for Bicycle Frame

This project focuses on the material and process selection for a road-racing bicycle frame, emphasizing the crucial role of the frame in upholding the bicycle's components. The student's objective is to choose a material that balances strength, weight, flexibility, and other key properties. After considering factors like tensile strength, stiffness, and fatigue strength, the analysis, supported by graphs and data from CES EduPack, concludes that Carbon Fiber Reinforced Plastic (CFRP) is the most suitable material due to its optimal combination of low density, reasonable price, and superior performance characteristics. The project also details the joining method, recommending Phenolic adhesives for a rigid and strong bond, and specifies filament winding as the shaping process for the carbon fiber components. This project provides a comprehensive overview of the material selection process, highlighting the considerations and rationale behind the final material and process choices for a high-performance road-racing bicycle frame.

Material and process selection for a
bicycle frame
The frame of any bicycle is considered to be the key element in its
structure. As it is responsible of upholding most of the bicycle’s
components such as the wheels, handles, axle, bars, etc. Therefore,
spending time and effort to choose the right material is essential. In order
to do that, determining the objectives of the bicycle and uses are
important, without it no final choice can be made.
A road-racing bike is to be my option of many types. As a result, the
chosen material must have three enquires: strength, weight and
properties.
Constrains and objectives the frame should fit:
 Light weighted frame.
 High tensile strength.
 Flexibility: to absorb road vibration.
 High fatigue strength.
 Low toughness.
 Low elongation.
 High stiffness.
 Comfortable.
Free variables:
 Cost.
 Color.

Graphs:
1- Price Vs. Density:
This graph illustrates the price of the materials against their densities. All showed
materials have fracture toughness less that 15 MPa (<15MPa).
From above, CFRP (carbon fiber reinforced plastic) appears to be the most suitable
material, as it has a low density and a reasonable price when compared with other
materials. Adding that in order to make one bike frame, around 40 layers of CFRP
are needed.
1- Younge’s Modulus Vs. Tensile strength:

As previously mentioned, high stiffness and tensile strength are the most required
properties I seek in a material. As this material must have the ability to resist
deformation and fracture. The graph above emphases on the fact that CFRP is the
most suitable material for a road-racing bike frame.
1- Fatigue Strength:

The bike frame must have significant high fracture strength as it is exposed to fails
and falls at high speeds. As it is clear in the graph, both stainless steel and CFRP
have a high fracture strength compared to other materials, so in this case the two
choices are possible.
1- Fracture toughness Vs. Compressive strength:

From the graph, both Aluminium and CFRP have fracture toughness smaller than
15 MPa (<15MPa). On the other hand, CFRP has a higher compressive strength,
which is a requirement. And that is because of the type of the bicycle, as it is a road-
racing bike that must endure long distances and a load from the rider’s body.
In conclusion, after analysing all the results from several graphs and databases from
CES Edupack, CFRP seems to be the best material for a road-racing bike. As it
meet all requirements and constraints.
The pros of selecting CFRP for a road-racing bike are:
 Very tough but at the same time very flexible, to allow the absorption of
vibrations and to endure the weight of the rider and hard falls and
collisions.
 Extremely light weight and comfortable when riding for long hours and
distances.
The cons of selecting CFRP for a road-racing bike are:
 Relatively expensive with other potential materials.
Joining Method:
Benefitting from the information and data from CES EduPack, I have concluded
that the joining method of the carbon fiber parts for the bike frame should be the
process “Phenolic adhesives”, in a joint geometry BUTT. This process gives a rigid
and stiff bond as it resembles chemically. Also giving the joining very high strength
and good water resistance as well as heat resistance/flame retardant. These
properties are well needed for frames of a road-racing bike as it accelerates to a high
speed while racing.

Figure1: Adhesives are applied by
spraying or with dispenser.
Figure 2: Shaping the Carbon fiber would be by
filament winding. This is by winding the resin-
impregnate reinforcement on a rotating mandrel.
This winding procedure is done to maximize the
performance of this application. Winding is
continued until the thickness of the required
material is achieved. As soon as the material is
hard it is pulled off the mandrel.