Special Issue Article

Proc IMechE Part P:

J Sports Engineering and Technology
1–11
Design and manufacturing of a Ó IMechE 2017
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DOI: 10.1177/1754337117716237

composite bicycle frame journals.sagepub.com/home/pip

Ali Amiri, Taylor Krosbakken, William Schoen,

Dennis Theisen and Chad A Ulven

Abstract
Carbon fiber composite frames were first used in Tour de France in 1986. With recent growth in research and develop-
ment of composite frames, carbon fiber composites have become more popular in bicycle industry where lightweight
and high stiffness are of upmost importance. Unfortunately, carbon fiber is expensive and has low impact toughness.
One method of overcoming this shortcoming is to hybridize carbon fiber with natural fibers such as flax. The benefit of
using hybrid composites is that the advantages of one type of fiber can overcome the disadvantages of the other type of
fiber. As a result, a balance in cost, performance, and sustainability could be achieved through proper composite material
design. In this study, carbon fiber was hybridized with flax fiber in an effort to manufacture a bicycle frame with the high-
performance characteristics of carbon fiber and low cost and renewability of flax fiber. In addition, vibration damping
properties of flax fiber will result in a more comfortable ride. The results of mechanical tests of the frame material
revealed that the manufactured frame possess similar or higher stiffness and strength as commercially available carbon,
titanium, and aluminum frames while exhibiting superior vibration damping properties. All these were achieved with a
lower cost compared to carbon composite frames while maintaining 40% biocontent.

Keywords
Bio-composites, carbon, epoxy, flax, hybridization, bicycle frame

Date received: 30 September 2016; accepted: 2 May 2017

Introduction equipment is one of the important factors in improving

cycling performance.5
Composites in bicycle industry
Sports and recreation applications are the world’s third
consumer of advanced composites following aerospace/
Hybridizing carbon and flax
defense and elastomer reinforcement.1 Utilization of On the other hand, high cost and low impact toughness
composites has been center of attentions for bicycle of carbon fiber composite frames can be mentioned as
design since 1980s.2 In bicycle industry, carbon fiber is one of drawbacks for these frames.3,4 One solution to
one of the most favorable reinforcement to be used in this problem could be implementing other types of
composite frames due to weight reduction and higher fiber, such as flax into composite frames to lower the
specific stiffness.3 The other advantage could be men- material cost and increase the impact toughness. While
tioned as the ability to manipulate the fiber orientation natural fibers offer competitive strength-to-weight ratio
in bicycle frames unlike in isotropic materials such as compared to synthetic fibers (i.e. glass and basalt) there
steel and aluminum.4 Carbon fiber bicycle frames were are other benefits in using them such as reduction in
first used in 1986 in the Tour de France with the weight
of 7–8 kg.5 A study was conducted in 2010 on three sig- Department of Mechanical Engineering, North Dakota State University,
nificant cycling races including Tour de France and Fargo, ND, USA
classic European races. It revealed that use of advanced
Corresponding author:
composite materials in Bicyles frames has been a factor Chad A Ulven, Department of Mechanical Engineering, North Dakota
in the progression of road cycling speed since 1990.6 State University, Dept 2490, PO Box 6050, Fargo, ND 58108, USA.
There are other studies that support the claim that Email: chad.ulven@ndsu.edu
2 Proc IMechE Part P: J Sports Engineering and Technology 00(0)

CO2 emission, less dependency on foreign oil sources, needed to be limited as much as possible in order to
reduction in energy consumption and the most impor- improve overall efficiency.29 These values were gained
tant one, recyclability.7,8 However, flax fiber, when by the testing of current aluminum and carbon fiber
compared to its synthetic or mineral-based counter- bike frames and will be discussed later in detail.
parts, generally has lower mechanical properties. A cost constraint, although hard to quantify, was
These low mechanical properties are a major inhibitor also considered that the manufactured frame should
when trying to develop high-performance prod- not exceed the price of an average aluminum frame
ucts.9,10 One method for increasing their level of which is approximately US$1000. Since complex manu-
mechanical performance is to hybridize flax fibers facturing methods will result in expensive tooling and
with synthetic fibers or mineral-based fibers.11,12 By overall expensive manufacturing process. Therefore,
hybridizing different types of fibers, the advantages another design constraint set for this project was incor-
of one type of fiber could compensate the shortcom- porating simple and inexpensive manufacturing
ings of the other types used in the hybrid composite. methods.
Through proper composite material design, tailored As result of this project, a method was developed to
properties, a balance in cost, performance, and sus- manufacture a carbon/flax hybridized bicycle frame, on
tainability could be achieved.4,13 a small scale production, with limited resources.
Another great advantage of flax fiber composites is Manufactured frame was testing in bending as well as
superior vibration damping properties. Due to unique vibration test to compare the performance with com-
structures, thermoset resins reinforced with flax fibers mercially available carbon and aluminum frames.
exhibit nonlinear behavior when subjected to load-
ing.14–16 This nonlinear response results in energy
loss.17 This is beneficial in the design of sports equip- Materials, design, and manufacturing
ment where vibration damping and comfort of the ath- Materials
lete using the equipment are desirable.18–20
Hybridizing is considered to be an effective method The carbon fibers used in this study were unidirectional
to improve damping properties of laminate compo- fabric mat GA130 manufactured by Hexcel
sites.21 Experimental studies22 as well as modeling of Corporation, Dublin, CA. The flax fibers used in this
carbon/flax hybrid composites23 show that the hybridi- study were manufactured by Composites Evolution
zation of flax and carbon fiber offers good potential Ltd., Chesterfield, UK. The flax fibers known as
for developing high stiffness composites for various Biotex Flax come in a unidirectional fabric. The epoxy
structural24 and sports applications while simultane- resin system used in this study was Super Sap One
ously incorporating biobased materials. Epoxy, with 20% biocontent mixed with Super Sap
One hardener from Entropy Resins Inc., Hayward,
CA. The epoxy resin system had a mixing ratio of 2
Project objectives and design constraints parts resin to 1 part hardener by volume.
At large-scale carbon fiber bicycle manufacturing facili-
ties, devices such as autoclaves, aluminum clamshell
Frame design
molds, and complex bladders are used. This very specia-
lized equipment can be used in a similar fashion to pro- The design of a bicycle frame is a stiffness based
duce flax bike frames. To cite some examples, Belgian design.30 When designed to have acceptable flexure,
bicycle company, Museeuw (Lokeren, Belgium) hybri- high ultimate strength is usually achieved. The maxi-
dizes flax fiber (FlaxpregÒ 2.0) with carbon fibers in mum amount of stress will happen at the end of each
their professional bike frames. They use the vibration frame tube. Therefore, in the design of the frame, at
absorption advantage of flax fibers for the comfort of the ends of every tube, an extra layer of carbon fiber
their users. There have been several studies done by was considered for holding the joint together as well as
Vanwalleghem et al. on effect of damping on bike providing additional stiffness.
frames and bike parts.19,20,25–28 Frame geometry influences the handling and ride
The goal for this project was set to manufacture a characteristics of bicycles.29 In this study, the frame
lightweight bicycle frame in the range of 1500–2000 g was designed for light off-road use, while being equally
while maintaining minimum 40% biobased content by capable on the road. It was a combination of the geo-
weight. The frame was to be designed in a way to metry of a current commercially available endurance
accommodate a 1.88 m tall rider and be able to fit 700C road bike and an off-road cyclocross race bike. The
size wheels with 34 mm wide tires and ample clearance important dimensions that were picked for the frame
for mud and debris accumulated on the tire surface. In are presented in Figure 1.
this manner, the static load the bike need to support is
a rider and gear weighing 115 kg. Stiffness/deflection of
the frame also needed to be considered. Vertical deflec-
Fiber orientation and layup
tion (in-plane) is desired to act as a suspension on To determine the fiber layup needed, couple of com-
rough surfaces. Horizontal deflection (out-of-plane) mercially available frames was measured for tube
Amiri et al. 3

corresponding to each member were calculated based

on the equivalent stiffness of the original design. The
thickness of each member was assumed to be 2.66 mm,
corresponding to five layers of flax fiber with one layer
of carbon fiber. Based on calculations of stiffness and
weight, the fiber layup was optimized for each tube.
Results of finite element (FE) analysis suggested fiber
layup for the bicycle frame. Figure 2 shows FE model
and deformation analysis for the frame.
After this step, an exact computer-aided design
(CAD) model was developed in PTC Creo Parametric
1.0 and weight of each layer per square millimeter of
carbon fiber, bi-directional flax, and unidirectional flax
composite, combined with epoxy at 50% fiber volume
Figure 1. Flax/carbon frame geometry.
fraction, was calculated. Using this information and a
developed excel spreadsheet, overall weight and bio-
based content of the frame was calculated and com-
diameter and wall thickness, and stiffness was calcu-
pared to goal values for weight and biobased content,
lated. Specialized brand bike models Tarmac and Allez
1500 g and 40%, respectively. Based on the results from
road bikes with aluminum and carbon fiber composite
FE analysis and excel spreadsheet, the final fiber layup
frame (Specialized Bicycle Components Inc., Morgan
was selected to manufacture the frame as presented in
Hill, CA) were cut into in order to take samples and
Table 1. The final weight of the frame was calculated
measure the dimensions of the tubes. The equivalent
to be 1426.5 g. Also, the flax content combined with
stiffness for carbon fiber frame was calculated using
the 20% biobased epoxy resin resulted in overall 40%
published data for carbon fiber (T300)/epoxy.31 These
biocontent of the frame.
values were used in order to establish a baseline stiff-
Moreover, based on the final layup, calculated stiff-
ness for determining fiber layup. The results are pre-
ness of the parts are presented and compared to those
sented in Table 2.
of carbon fiber and aluminum frame in Table 2. The
With a combination of bending and torsional loads,
the tube layups were considered to have a combination
of 0° and 45° orientation. The parts such as down tube,
Table 1. Final fiber layup for designed frame.
chain stays, and top are exposed to more torsional
loads compared to seat stays and seat tube and there- Part Fiber layup
fore had to have more 645° plies.31
ANSYS 14.0 Classical was used along with a slightly Top tube [0F/0C/45F/–45F/45F/–45F]
Down tube [0F/0C/45F/–45F/0F/45F/–45F]
simplified model of the frame to investigate the effects Seat tube [0F/0C/45F/–45F/0F2 ]
of changing material layups. The model was created
Seat stay [0F/0C/0F/45F/–45F]
in PTC Creo Parametric 1.0 with the same overall
Chain stay [0F/0C/45F/–45F/45F/–45F]
dimensions of the actual frame. The cross sections sim-
plified to straight, circular cylinders and the radii C: unidirectional carbon fiber; F: unidirectional flax fiber.

Figure 2. Displacement contour plots for designed frame.

4 Proc IMechE Part P: J Sports Engineering and Technology 00(0)

Table 2. Calculated frame bending stiffness for different frames.

Carbon frame (GPa) Aluminum frame (GPa) Carbon/flax frame (GPa)

Vertical Horizontal Vertical Horizontal Vertical Horizontal

Top tube 3.50E + 09 3.50E + 09 1.34E + 08 3.40E + 09 1.13E + 09 2.96E + 09

Down tube 3.80E + 10 3.80E + 10 5.92E + 09 5.92E + 09 5.91E + 09 5.91E + 09
Seat tube 3.40E + 09 3.40E + 09 1.50E + 09 1.50E + 09 1.06E + 09 1.06E + 09
Seat stays 4.75E + 08 4.75E + 08 NA NA 3.80E + 08 1.75E + 09
Chain stay end 1.21E + 09 6.60E + 08 6.90E + 08 1.60E + 08 3.75E + 09 1.36E + 09
Chain stay mid 1.21E + 09 6.60E + 08 6.90E + 08 1.60E + 08 1.35E + 09 5.30E + 09

horizontal bending stiffness (out-of-plane) is of high together and eliminated the risk of tubes accidentally
importance and interest, since it will affect the efficiency changing dimensions. The jig was designed with the
power transfer. On the other hand, less vertical bending capability of being modified to accommodate different
stiffness (in-plane) will contribute to a smoother ride. In style bike frames.
the carbon/flax frame, the down tube is stiffer than in
the carbon frame and has the same stiffness as the alu-
minum frame. The top tube, being the farthest from the Manufacturing
power input, is not as stiff as the carbon or aluminum Design and manufacturing the frame. Based on the exact
frame in the horizontal direction. Seat tube stiffness is CAD model, wooden plugs were manufactured and
not as high as the carbon frame but comparable to the sprayed with a Duratec surfacing primer (from Fiber
aluminum frame; in addition, the seat tube tapered dra- Glast Development Corp., Brookville, OH), sanded,
matically to the width of the bottom bracket providing and buffed to a very smooth surface finish. Tag board
additional stiffness in the horizontal direction. Also, was attached to the plugs creating a lip and a parting
compared to the carbon frame, seat stay has a compa- line that gave the molds flanges and created two halves.
rable horizontal stiffness but less vertical stiffness. It is Pegs were also added to the tag board to create a hole
worth mentioning that the tubes used in this frame did in the first mold half and a matching peg in the second
not have circular cross section; therefore, the in-plane to ensure proper alignment.
and out-of-plane stiffness were different. A release agent was applied to the plug and tag
During assembly of the frame, in order to make sure board to ensure proper release of the molds once com-
the frame stayed square during assembly, a frame jig plete. 186 Black Tooling Gel Coat (from Fiber Glast
was designed and manufactured. The frame jig held the Development Corp., Brookville, OH) was painted onto
fully cured tubes in place so they could be glued one half of the plug and onto the tag board. This cre-
together and eliminated the risk of tubes accidentally ated the surface of the mold and ensured a hard, dur-
changing dimensions. The jig was designed with the able, and smooth mold surface. Manufactured wood
capability of being modified to accommodate different plugs and tag board parting line are shown in Figure 3.
style bike frames. Once this gel coat was partially cured, fiberglass and
During assembly of the frame, in order to make sure epoxy resin were added to reinforce the gel coat as well
the frame stayed square during assembly, a frame jig as create the mold structure. After the first half was
was designed and manufactured. The frame jig held the cured, the tag board was removed from the mold and
fully cured tubes in place so they could be glued plug, leaving the plug still attached to the first mold

Figure 3. (a) Wooden plugs and (b) plugs with tag board parting line as the first step to manufacture the mold for the frame.
Amiri et al. 5

Figure 4. Steps taken to manufacture the mold to manufacture the frame: (a) tooling gel coat applied, (b) fiberglass reinforcement
added, (c) ready for second mold half, and (d) one of the finished molds (half).

half. The same steps were then followed to create the

second half of the mold. When the second half was
cured, wedges were used to separate the two mold
halves and the plug was removed. This process was
repeated eight times to create two part fiberglass molds
for all the different tube shapes with nice polyester tool-
ing gel coat surface. A shot of these steps are shown in
Figure 4.
In addition to mold manufacturing, vacuum bagging
film was cut and sealed using heat in a shape similar to
the silicon bladders, with the silicon bladders inside to
create the structure needed in order to wrap fiber
around the bladder. A hose was fitted to one end in
order to inflate the bladder.
Mold surface was cleaned and coated with mold
release agent. The carbon fiber and flax fiber fabrics
were, cut to shape and wetted with epoxy resin, then
wrapped around the bladder in the specific layup order
and fiber orientation for each part. The bladder with
fabric wrapped around it was placed into one half of
the mold and the mold was closed and c-clamps were
used to hold the two mold halves shut. A regulator was
attached to the bladder hose to ensure stable pressure
throughout the resin curing process. This entire setup
Figure 5. Setup for manufacturing frame parts showing can be seen in Figure 5. The part was held under pres-
pressurized mold waiting to cure. sure of 200 kPa for 8 h to let the resin cure, and then the
6 Proc IMechE Part P: J Sports Engineering and Technology 00(0)

Figure 6. Carbon fiber dropouts: (a) first cut, (b) sanded dropout, and (c) completed and being installed on frame.

Figure 7. (a) Joining the tubes together using a 3M epoxy adhesive at the bottom bracket joint and (b) top tube, seat tube, and seat
stays junction.

entire mold was placed in a convection oven at 80 °C to hold it in place. Figure 7(b) shows one of the joints
for an hour to post cure the resin. under seat post. The cables for the break system were
The rear dropouts (slots on the frame that the axle run internally in the frame tubes, and the cable stops
attaches to) were designed and manufactured in the were glued onto the seat stay.
laboratory, while front dropouts were on a fork that
was purchased. Dropouts were manufactured from car-
bon fiber/epoxy composites, cut, and sanded to desired Characterization methods. Frame stiffness was measured
shape. The plugs were then inserted into the seat stays using the Rinard frame deflection test as specified by
and chain stays and secured with epoxy resin. This Rinard32 and used by Flynn et al.33 To perform the
interface was further strengthened by an additional test, the bottom bracket of the bicycle frame (where the
layer of carbon fiber. Figure 6 shown dropouts during crank arms are attached to the frame) was fixed and
manufacturing and after installation on the frame. the frame was held in a horizontal position and the
The flax fiber and carbon fiber composite tubes were deflection of the frame is measured as the load was
trimmed to length and mitered and were held in place applied.
using the frame jig. A 3M DP190 epoxy adhesive (3M, The Rinard frame deflection test setup is shown in
Maplewood, MN) was used to bond the tubes together, Figure 8. The stiffness of the front triangle plays a key
as shown in Figure 7(a). An additional layer of carbon role in overall handling characteristics of the frame
fiber in the form of fiber sleeve was impregnated with while the rear triangle stiffness affects the drive train
epoxy resin, was cut, wrapped, and placed onto the efficiency.29 In order to measure the front triangle stiff-
tubes to cover the joint section. Carbon sleeve was ness, a stiff steel rod was placed in the head tube in
sealed under a vacuum bag and was remained under order to act like a fork. A force of 211.3 N was applied
vacuum until the resin was cured. In order to secure the 230 mm from the bottom of the head tube. To measure
seat post inside the seat tube, a slit was cut to allow a the rear end deflection of the frame, an axle was placed
slight change in diameter and a metal clamp was used in the rear dropouts and a force of 211.3 N was applied.
Amiri et al. 7

Figure 8. (a) Rinard frame deflection test setup adapted from Rinard,32 (b) bottom bracket, (c) front triangle deflection test, and
(d) rear triangle deflection test.

Three-point bending tests were performed on tubes where d is the log decrement, x1 is the amplitude of one
cut out from commercial bike frames as well as frames wavelength, and xm + 1 is the amplitude of a wavelength
designed in this study. Bending tests parameters and m cycles away from x. The damping ratio z was then
support spans were set based on the ASTM D790. A calculated using
MTS Servohydraulic Model 312 (from MTS Systems d
Corporation, Eden Prairie, MN) was used with the z= ð2Þ
2p
cross-head displacement rate of 3 mm/min. Maximum
flexural stress and flexural modulus of specimens were
An Omron Z4M-S40 laser displacement sensor was
calculated based on the ASTM D790.
placed at the tip of the free end and was connected to a
In this study, a composite layup similar to the one
data acquisition system. LabView was used to generate
used in the frame was manufactured to test and charac-
voltage versus time plots which were then used to deter-
terize vibration damping properties. In addition, the
mine vibration characteristics. Voltages versus time
vibration test was performed on carbon fiber compo-
plots were generated by running LabVIEW by displa-
sites, flax fiber composites, aluminum, steel, and tita-
cing the tip of the sample and then releasing the sam-
nium specimens to compare the properties.
ple. The plotted data revealed a sinusoidal wave whose
Vibration tests were performed similar to a previous
amplitude decreased logarithmically with time. The
study4 by placing a 304.8 mm 3 25.4 mm specimen
process was completed three times in order to achieve
between a cast iron machining block and a block of
an accurate sampling set. The laminate’s damping
aluminum. The specimen was then secured into place
ratios were calculated from the obtained plots.
by tightening a c-clamp on the outside surfaces of metal
An alternate method of measuring vibration damp-
pieces. The resulting setup formed a fixed end cantile-
ing is to use free flexural vibrations test setup as out-
ver beam.
lined by Assarar et al.23 In this method, in order to
To find the damping ratio, the log decrement was
achieve free-free boundary conditions and less scatter
determined using the following equation34
in obtained data, specimen is hung vertically by rubber
 
1 x1 threads and then is excited by an impulse hammer or
d = ln ð1Þ by a loud speaker as used by Vanwalleghem et al.25
m xm + 1
8 Proc IMechE Part P: J Sports Engineering and Technology 00(0)

15% compared to non-hybrid carbon fiber composites.

Le Guen et al.35 studied the mechanical properties of
carbon–flax–epoxy composite laminates. Their tests
revealed that hybridizing carbon and flax fiber resulted
in composites with four times higher damping coeffi-
cient compared to composites using carbon fiber alone
as reinforcement. In addition, in a previous study done
on hybridization of flax fiber and carbon fiber at North
Dakota State University,4 a single cantilever beam
vibration test was utilized to study vibration damping
behavior of composites reinforced with plain carbon
fiber, flax fiber as well as hybrid carbon/flax samples.
Figure 9. Average horizontal deflection for frames with The results showed that with an increase in alternate
different materials. fiber loading, there is an increase in composite damping
ratio. This increase in damping ratio corresponds to an
improvement in vibrational damping characteristics of
Results of analysis a structure. The results revealed that as ratio of flax
fiber to carbon was increased, so was the vibration
The stiffness of carbon, aluminum, and manufactured damping capabilities of the composite.
flax/carbon frames was measured using Rinard frame Extra manufactured frames and rejected frames
deflection method. The stiffness of front and rear trian- due to surface flaws, as well as tubes from commercial
gles was measured as described previously (two mea- bikes were tested in three-point bending. Results of
surements from each frame) and average value of front flexural tests are presented in Figure 12. For both
and rear deflections is presented as the overall stiffness tested tubes, flax/carbon showed higher or the same
of the bike frame in Figure 9. The results show that the modulus. Also, in both tested tubes, carbon/flax
flax frame is 95% as stiff as the carbon fiber frame hybrid composite specimens reached higher amount
tested. The goal for this frame was to be stiffer than of load. It is worth mentioning that in carbon/flax
aluminum and this was achieved while almost reaching
frame tubes, wall thickness was thicker. The diameter
the stiffness of the carbon fiber frame.
of the down tube was limited to the standard width of
Vibration damping ratios of flax, carbon/flax, and
the spindle of the pedals; therefore, the diameter was
carbon composites as well as titanium, aluminum, and
maximum to reach higher stiffness. Therefore, indi-
steel coupons are presented in Figure 10. As expected,
vidual members of this flax/carbon fiber bicycle frame
plain flax fiber composite had the highest damping ratio
showed higher strength and stiffness compared to
followed by carbon/flax hybrid composite.
commercially available bike frames.
Figure 11 shows the raw displacement data of hybrid
carbon/flax composite and the titanium specimen. Both
specimens started with the same deformation, but as
Conclusion
seen, flax/carbon composite damped the vibration
much faster than titanium specimen. This project has explored the use of flax as a structural
The results presented here are in agreement with pre- component in a bicycle frame. Through testing other
vious studies conducted on damping properties of com- common frame materials, it was discovered that flax
posites incorporating flax fiber. Assarar et al.23 studied had superior damping characteristics compared to alu-
vibration damping properties of hybrid carbon–flax minum, carbon fiber, titanium, and steel. A prototype
reinforced composites. Their results showed that damp- bicycle frame made of approximately 70% flax fiber
ing properties of their composites were improved by and 30% carbon fiber was manufactured using the

Figure 10. Coupon damping ratios of different materials tested.

Amiri et al. 9

Figure 11. Displacement of titanium and custom (carbon/flax composite) frame.

Figure 12. Load versus deformation results for (a) seat tube and (b) down tube for three different frames.

Figure 13. A photo of complete bicycle using manufactured hybrid carbon/flax composite frame.
10 Proc IMechE Part P: J Sports Engineering and Technology 00(0)

manufacturing process designed. This frame had a bio- unique progression of road cycling speed in the last
based content of 40% using a 20% biobased epoxy 20 years. J Sports Sci 2010; 28(7): 789–796.
resin. This prototype frame was tested for horizontal 7. Fowler PA, Hughes JM and Elias RM. Biocomposites:
stiffness and proved to be nearly as stiff as a carbon technology, environmental credentials and market forces.
fiber frame and stiffer than all other frames tested. So J Sci Food Agr 2006; 86(12): 1781–1789.
8. Amiri A, Yu A, Webster D, et al. Bio-based resin rein-
in conclusion, a flax fiber bicycle frame can be made as
forced with flax fiber as thermorheologically complex
stiff as carbon, lighter than aluminum, and damping
materials. Polymers 2016; 8(4): 153.
characteristics better than all common frame materials. 9. Taylor C, Amiri A, Paramarta A, et al. Development
Because of manufacturing limitations, the fiber vol- and weatherability of bio-based composites of structural
ume fraction that was designed was not able to be quality using flax fiber and epoxidized sucrose soyate.
reached, and therefore, the final weight of the bike was Mater Design 2017; 113: 17–26.
about 2100 g. Once a proper fiber volume fraction is 10. Amiri A, Hosseini N, Ulven C, et al. Advanced biocom-
obtained in combination with fewer layers in key areas posites made from methacrylated epoxidized sucrose
as established using FE analysis, a frame weight under soyate resin reinforced with flax fibers. In: Proceedings of
the goal of 1500 g can be achieved. The final price of the 20th international conference on composite materials
materials and purchased parts was US$1350, not (ed A Amiri, N Hosseini, C Ulven, et al.), Copenhagen,
including the bikes that were cut into for testing and 19–24 July 2015. DOI: 10.13140/RG.2.1.1062.8965.
11. Petrucci R, Santulli C, Puglia D, et al. Mechanical char-
measurements.
acterisation of hybrid composite laminates based on
A photo of the finished bike is shown in Figure 13. basalt fibres in combination with flax, hemp and glass
In addition to mechanical tests and characterization fibres manufactured by vacuum infusion. Mater Design
methods, the finished bike was ridden and tested for 2013; 49: 728–735.
well over 500 miles, in one 100-miles gravel races as well 12. Ashworth S, Rongong J, Wilson P, et al. Mechanical and
as routing weekly rides. During test ride, the vibration damping properties of resin transfer moulded jute-carbon
damping properties in small scale have shown to be hybrid composites. Compos Part B: Eng 2016; 105: 60–66.
effective in the entire composite structure in providing 13. Bagheri ZS, El Sawi I, Schemitsch EH, et al. Biomechani-
a smooth ride quality. Several experienced cyclists have cal properties of an advanced new carbon/flax/epoxy
ridden the manufactured bike and all agree that it has a composite material for bone plate applications. J Mech
very unique ride quality. However, it is hard to quan- Behav Biomed 2013; 20: 398–406.
14. Newman RH, Battley MA, Carpenter JE, et al. Energy
tify this nonscientific claim, even though the findings of
loss in a unidirectional flax-polyester composite subjected
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47(3): 1164–1170.
Declaration of Conflicting Interests 15. Amiri A and Ulven C. Bio-based composites as thermo-
The author(s) declared no potential conflicts of interest rheologically complex materials. In: Antoun B, Arzou-
with respect to the research, authorship, and/or publi- manidis A, Qi HJ, et al. (eds) Challenges in mechanics of
cation of this article. time dependent materials, vol. 2. Cham: Springer, 2017,
pp.55–63.
16. Amiri A, Ulven CA and Huo S. Effect of chemical treat-
Funding ment of flax fiber and resin manipulation on service life
The author(s) received no financial support for the of their composites using time-temperature superposition.
research, authorship, and/or publication of this article. Polymers 2015; 7(10): 1965–1978.
17. Fereshteh-Saniee F, Majzoobi G and Bahrami M. An
experimental study on the behavior of glass–epoxy com-
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