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Bicycle Frame Materials


Throughout history the concept of the bike has been used and manipulated with materials from all over the spectrum exercised. Lately, machining methods have become advanced enough to control all different marks of metals, from typically the most popular being steel, to alloying titanium based mostly alloys, however not only metallic materials are being used. Carbon fibre, a universal term of the structure of carbon fibre weave and epoxy resin, is the world's most recent popular material to be utilized on basically everything in the automotive industry, from products knobs to the entire framework on the Porsche Carrera GT for example, which is little by little expanding in to the bi-cycle market and beyond. Nowadays bicycle manufacturers provide an apparent unlimited array of materials, joining techniques and concluding techniques, that ought to theoretically be able to produce the "best" bicycle frame on the market. Taking present day complications into account, the "best" bicycle body material(s) are perhaps inappropriate in conditions of processing price and market sale value. Despite this, using Cambridge Anatomist Selector (CES Software), by establishing engineering constraints, considering material selection indices and loading patterns on components; an individual "best" material is usually to be determined.

Product Definition

As not absolutely all bicycles are targeted at the same individual market, with the motive to design a bike for different purposes such as; pile bikes, city bikes, leisure bikes, road bikes, competition bikes, etc. the constraints and objectives of the way the bicycle body should react under pressure during use will vary. It is because of this, the "best" materials can differ from bi-cycle type, and for that reason a category of cycle must be specified.

The bicycle category to be given is a tiny sub-category of street bikes called set items bikes or "fixies". This group of bike has sprung up all over the world, with its major uprising leading back again to Brooklyn, NY; however a cult following has arisen in major metropolitan areas around the world. This type of bicycle and cycling style lends its origins back to keep track of racing, where in fact the same design of bike is used in the Olympics and other motorcycle sporting events. The fixie style is becoming popular on the road because of its agility and acceleration around town for commuting as well as its fitness affiliation for of course only having one equipment. This sub group of cycle is often used for part recreation, part fitness use, yet mainly as a way of transport in and around town.

This recent uprising has uncovered numerous materials of bike framework, from old 1980's track bikes made from steel to recently created aluminium and carbon fibre composite frames which are being used on this kind of bike and design of riding.

Materials Selection Possible Constraints

The shape components will be subject to different forces, which several will go through the same force depending on different launching conditions. The seat pipe will experience regular compression pushes from the weight of the rider as well reactions from road pushing support to the rider, whereas the down pipe will experience tensional makes having the crank area together with the fork set up; however braking gives surge to compression. Other features like the seat stays will experience frequent compression and lateral stress from the braking mechanisms, of which tightness is a vital property of the materials. Young's modulus or rigidity is also very important in the design of the forks credited to instantaneous braking pushing the forks to flex.


The denseness of the materials will impact highly the efficiency and feel of the bike when ridden. More energy must brake or speed up the bike that has a high density body, consequently making the bike hard to control and manoeuvre. A light and portable material is vital to create the perfect bicycle frame to improve manoeuvrability, braking and acceleration performance. That is why a constraint of thickness is to be limited at 5000 KG/M^3. This includes common body materials such as aluminium and titanium alloys. [4]

Young's Modulus

The stiffness of the framework is vital to avoid plastic material deformation of the body when ridden over obstructions, however if the shape is too stiff there will too much vibration from road areas. A constraint of materials above 30GPa are satisfactory for the intended use, however materials above 400GPa are considered too stiff and will cause a harsh incontrollable bi-cycle. [4]

Tensile and Compressive Stress

Tensile stress occurs on lots of the the different parts of the bicycle body and is a faltering property by overloading the body which consequently helps it be a high goal factor. Materials above of tensile stress value 300MPa and above are acceptable. Compression is also a major stress force loaded in the bicycle shape, in places like the rear seat keeps and seat pipe from gravity pulling the weight of the rider toward the bottom. Poor compressive makes will translate into a mess of buckled piping. [4]

Yield Strength

The yield power determines the amount of force required to plastically deform the material of which the materials is entirely deformed after yielding. This can be applied to abrupt impacts or higher launching of the frame which can result in inability of the frame, perhaps leading to personal injury when ridden. The bigger the yield strength, the higher pressure the frame will be able to hold up against which is favourable in frame design. [4]


Elongation pertains to brittle and ductile properties of an material, where high percentage elongation leads to ductile properties and low percentage elongation brings about brittle properties. If a materials is too brittle, it theoretically could fracture into small parts which are to be avoided when bicycling. It would be preferable for the material to plastically deform to a large extent before failing as this will prevent damage if an abrupt stop is experienced. A material with an extremely raised percentage elongation is also to be avoided as the framework will not keep its form and deform with the weight of the rider. Materials below 40% elongation provides favourable elongation properties. [4][5]

Fatigue Strength

The maximum cyclical tensions can be analyzed and applied to a bicycle body immediately, mimicking the repetitive strains when ridden. This may therefore extrapolate the life of the bicycle frame given the quantity of repetitive weight applied when ridden. [4][5]

Torsion Stress

Torsion launching occurs upon acceleration of the bicycle where the body is moved laterally under the lateral forces applied by the rider from the torque applied. The usual lateral launching on the framework is used in slight longitudinal loading. The torsion capacities of the material must be taken into account which also highly impacts the joining techniques of the bicycle frame. [4][5]

Material Aims Set-up and Index Selection

To find the "best" material for a fixed gear bike structure, the main objective is to prioritise engineering performance; reducing weight, increasing rigidity. The agility of the framework is the key characteristic of which turning reactions, acceleration and deceleration performance are vital to a successful fixed gear cycle to be utilized around town as well as for training purposes.

The indices used to insight into CES will define stiffness-limited design at least mass.

The structure features that are tensile loaded, creating a tie between two other frame beams use the index Young's Modulus / Thickness, E/. Increasing this index will discover appropriate materials that exert stiffness, combined with low denseness, however also giving the best tensile properties.

The compression index, for components filled in compression, is (Young's Modulus ^ Ѕ)/Density, E1/2 / will also identify the best materials for your type of launching. For components packed in bending the index (Young's Modulus ^ Ѕ)/Density, E1/2 /, will also be used.

For durability limited design, locating the best material for tensile durability before yielding and plastic deformation of the shape occurs, the index yield power/density, Жf /, is to be used. Locating the best materials for compression power will also utilize this index. For the seatstays and fork components, packed in bending, the index Жf2/3 / will be utilized.

Maximising these indices will locate the best materials for each and every specified kind of loading. [6]

Outcomes using CES

Function: Bi-cycle frame

Constraints: Should never fail under rider weight and road reactions.

Objective: Overall mass of bike frame is to be reduced, without compromising stiffness and power.

Variables: Material choice, materials section shape, concluding techniques.

Before inputting constraints, the graphs of Young's Modulus over thickness and yield power over density seem as follows using education level 2:

Figure 5. Young's modulus over denseness CES.

Figure 6. Produce strength over thickness. CES.

Inputting the constraints, CES outlines sets of materials that meet up with the constraints:

Figure 7. Young's modulus over denseness using constraints. CES.

Figure 8. Yield strength over density using constraints. CES.

CES software has defined different materials from the teams: composites, metals and alloys, and technological ceramics. These materials are:

Aluminium alloys

Titanium alloys

Beryllium alloys

Carbon fibre composites

Magnesium alloys

Silicon based complex ceramics

Aluminium alloys

Aluminium alloys are extremely light and shows signals of high elongation, these factors direct aluminium toward being truly a good applicant for a bi-cycle frame, however aluminium has a low young's modulus value and certain alloys show low tensile strength worth. These properties may give the bicycle frame flexibility, however current aluminium bicycle frames aren't flexible as they generally have a larger diameter top pipe and basic radii in the framework components to counter work this. The exhaustion ideals for aluminium alloys are very low, which indicates that after some time the structure will split and fail, which is definitely something to avoid. Current bike shape manufacturers use butting technology in aluminium structures to combat this, by increasing the thickness of the pipe at where in fact the material is necessary most. [4]

Titanium alloys

Titanium alloys remain twice the weight of aluminium alloys, yet around 50 percent that denseness of metal alloys, making up because of this will be the high tensile power and Young's modulus prices which enable to style to be produced from thinner tube portions than aluminium which reduce overall weight. The tiredness principles are also high meaning the frame can last for a long time. [4][7]

Magnesium alloys

Magnesium alloys are even lighter than aluminium alloys and have a just a little better exhaustion value. Magnesium alloys also have a low Young's modulus value, lower than aluminium which indicates flexible shape properties that will have to be yet again fixed using tube section width design. Magnesium alloys look appealing and also have good properties that may be applied to a bicycle structure, nonetheless they have low corrsosion level of resistance which needs to be triumph over by surface treatments. On the existing market, few casings have been made from the materials as they tend to be very costly. [4][7][8]

CFRP, Carbon Fibre Re-enforced Plastic

CFRP, a composite material, is lighter than all the metals earlier mentioned as well as having high a Young's modulus, tensile value, and relatively high exhaustion strength beliefs. This material is currently being used all around the bike market, from strictly track bicycles to road racers, complete structures or part CFRP casings, and components used in mountain bicycle off road casings. The modulus of the epoxy resin is extremely low, producing a brittle materials; which consequently affects the method which the CFRP tiers are applied. CFRP has good tensile properties, however not so high compression or torsion properties, therefore the angle of which the carbon fibre tiers are applied must be taken into consideration, in any other case turning bends could convert the frame into a fractured chaos. That is also obvious in the extremely low elongation value, 0. 032% - 035% [3][4][8]

Technical Ceramics, Silicon Carbide

Silicon carbide, unlike ceramics generally speaking has a good tensile value similar compared to that of titanium, aluminium and CFRP, and a young's modulus value four times that of titanium. Therefore that silicon carbide has a favorably good outlook on the perspective bicycle framework, displaying high tiredness values and having a slightly lower density than titanium. Silicon carbide does indeed however have a minimal ratio elongation at 0% [3] which features the prospect of producing a cross material to increase this value. [4][11] [10]


Beryllium is often used as an alloying materials to increase hardness properties, nonetheless it also has an extremely high young's modulus value and is lightweight. Beryllium could not be used to solely create a bicycle shape as it is poisonous, especially with inhalation. [12][5][4]

It is noticeable to start to see the sets of materials commonly applied to bicycle frames from the graphs produced; however there aren't any specific materials shown. Enabling education level 3, the repository of materials becomes more specific and materials that not meet up with the constraints are overlooked. By maximising the indices, specific materials can be identified.

CES software has located Cyanate ester/HM carbon fibre UD amalgamated 0 lamina by maximising the indices as the best material for a bike shape. The unidirectional lamina allows the tensile and young's modulus ideals to be standard within the materials, rather than have a directional stream providing room for failure by torsion. The composition of 30-40% polymer and 60-70% carbon fibre sustains a high level of stiffness and tiredness durability from the carbon fibre and reduces the brittle properties of the polymer resin.

The CES end result may have located the "best" material for a fixed gear bike shape, with the aim minimise the weight of the entire frame, without compromising stiffness and durability, however joining procedures, surface treatments/coatings and forms have to be considered.

Joining processes

Current CFRP structures are either manufactured by using tubular lugs of aluminium or titanium, and then pre-made CFRP pipes aligned and trapped into place with further layered CFRP and epoxy adhesives. The subscribing to between your two different types of materials has led to corrosion and faltering, which has aimed manufacturers to produce frames solely using CFRP. Constant laminating can be used to cover a mandrel which removing the mandrel gives go up to a designed tube or hollow section essential for the specified element. One method used to build low batch numbers of CFRP frames is autoclave moulding, which builds up the CFRP layers by hand, this technique creates a monocoque CFRP shell which has superior stiffness, strength and is extremely lightweight; frames lower than one kilogram have been produced. [8]

Shape Factors

Cyanate ester/HM carbon fibre UD composite 0 lamina has a maximum condition factor value for stretchy bending (Maximum eB) of 12. 3. Employing this value, the shape efficiency can be compared against other materials determining if other materials display better stiffness and level of resistance to bending properties.

Using CES a graph can be drawn of Young's modulus over thickness with the index /E1/ 2, which will show the utmost bending stiffness whilst minimizing weight. As the form of the materials is not set, generally materials used for light and portable structural aims require low /( eBE)1/2 values. The materials will be determined as they provide the best properties. [10]

By comparing alloys used frequently in the produce of bicycle casings up against the CFRP based materials CES located, it is possible to see the advantages of firstly the form factor related to aluminium, offering it good structural properties despite its low young's modulus value. However the lower value of the driven CFRP material means so it has better form efficiency and can have better in service properties at providing a light stiff bicycle framework, repellent to bending causes.

The titanium, given its tightness will be able to produce a lighter structure than one manufactured from steel and aluminium, yet doesn't have a much better bending shape factor shown by the aluminium alloy. Magnesium, despite having the most affordable modulus has a maximum bending factor lower than the aluminium alloy, which is one of the reasons why it is becoming an increasingly popular base alloy for bicycle frames. [10]

Hybrid Bike Frame

The extreme stiffness of the Cyanate ester/HM carbon fibre UD composite 0 lamina bike frame will create an extremely stiff ride, which the road surface will be sensed through the shape to the rider. One way to avoid this is to use bigger or thicker tyres, which will reduce vibration, however will significantly increase friction and reduce top swiftness and acceleration times. A method to reduce these problems would be to develop a framework that utilised a couple of materials and combined them together to give longitudinal damping properties yet keep up with the transverse stiffness and light properties. This may be attained by using titanium on the primary triangular frame due to its 5-10% elongation property, extremely high tiredness, tensile and light-weight properties; and using the CFRP on the chain stays, seat keeps and fork components for its extremely high shape factor and bending stiffness value. This may also create a high fatigue level of resistance of the frame making it previous for many a long way of riding, however problems might occur with the getting started with of both materials when using acrylic based or epoxy glues to bond both sections collectively as this interferes with the structure and may lead to corrosion or inability from loading. [8][7][6]

A hybrid material could be response to creating the perfect bicycle framework using silicon carbide, boron carbide and aluminium, also called MMC duralcan alloys, or alumina B4C alloys. Alloys using these materials have been created, utilizing silicon and boron carbide's mechanised properties and combining them with aluminium's structural advantages.

The aluminium carbide composites exhibit good bending factor worth as well as high Young's modulus ideals, fatigue strength, tensile strength and very high compressive strength, which makes the material promising for use as a bicycle frame.

Surface Treatments

Surface treatments such as anodizing are normal in today's current bike market, for example on aluminium where the reactive surface is protected with an oxide covering and the thickness controlled using anodizing. This prolongs the life of the framework by reducing the risk of corrosion. Electroplating is also used for corrosion amount of resistance or to improve hardness, this method is usually applied to metals; however non-metals can be plated once coated with an electrically conductive material. This can give metals bright mirror coatings, synthesizing the appearance of commonly expensive materials such as yellow metal or sterling silver. For metals and non-metals, organic and natural solvent structured paints are widely used to give the frame interesting colours and finishes. Organic solvent based mostly paints are usually applied to carbon fibre; nonetheless it may also be preferred showing the design of the carbon fibre in its natural form demonstrating the weave routine. [4][10]


The best materials for a fixed gear road motorcycle come by means of carbon fibre re-enforced plastics; this is due to light in weight, high modulus structures they create. The form factor contributes highly to the success of the materials by creating stiff tubular portions that are immune to bending and plastic material deformation also advanced by their high produce strength principles. The tensile and compression properties shown by the materials are very high and work well at absorbing impact, distributing the strain throughout the framework. The orientation of the carbon fibre is very important as this impacts the tensile and compression principles that the material may take before fracture in the longitudinal and transverse directions, essential to the structure residing in one part when turning, decelerating or accelerating quickly. A uni-directional laminate is preferable as the fibres provide ideal stress and stress abilities.

The metals brought up provide lightweight solutions to the bicycle shape; however each has issues, whether it is low young's modulus or tiredness limits that require to be attended to. These issues are usually resolved through alloying or using form factors to increase or lower tube thicknesses or use of butting and other becoming a member of processes.

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