Design and manufacturing of a hybrid flax/carbon fiber composite bicycle frame

Abstract

Carbon fiber composite frames were first used in Tour de France in 1986. With recent growth in research and development 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 highperformance 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.

Review on Hybrid Carbon/Flax Composites and Their Properties

“…Particularly, the damping coefficient of composites reinforced with flax fibers is found to be 4 times higher than that of composites reinforced with carbon fiber 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 [8,9,12,13,15,17,21,22,26,40,43,45,46,[51][52][53][54][55]. [8,9,12,13,15,17,21,22,26,40,43,45,46,[51][52][53][54][55].…”

“…A hybridisation of carbon with flax fibers to improve the damping properties of carbon composites is promoted by the high damping ratio of flax fibers in comparison with titanium, aluminium, steel, or carbon [8]. Furthermore, the damping of nonhybrid flax fiber laminates is significantly higher than the damping coefficients of nonhybrid carbon fiber laminates [24].…”

“…However, in the last 5 years, the potential of the hybridisation of flax with high-performance expensive carbon fibers has been actively investigated. This type of hybridisation is especially interesting for the fields where mechanical performance and low weight are more significant than the cost of the corresponding construction part, like, e.g., sport and leisure [8], orthopaedic implants [9], or the automotive, especially racing car, industry [10,11].…”

“…Remarkably, according to Table 3, only epoxy resin is used as a polymer matrix in all of the reported studies. At the same time, two studies report the use of a partially biobased epoxy resin [8,22]. Consequently, further increasing the amount of a bio-based content in the carbon-/flax-epoxy composites contributes to environmental conservation.…”

“…(1) Impregnation of textiles one by one with resin (2) Curing at 35°C/3 h/5 bar [14] (1) Impregnation of textiles with resin (2) Curing in 2 steps: 200 kPa/8 h and 80°C/1 h [8] (1) Impregnation of textiles with resin (2) Curing in 2 steps: 10 bar/RT, 24 h [20] (1) Impregnation of textiles with resin (2) Curing in 3 steps: at RT/0.9 bar/24 h and 80°C/30 min and 130°C/60 min [19] (1) Impregnation of textiles with resin 7 International Journal of Polymer Science temperature, the cross-linking between the resin and the hardener starts and progresses, so that the epoxy matrix becomes solid. During the second curing step (or postcure), the composite is subjected to a higher temperature for a shorter time, so that the cross-linking between the resin and the hardener is completed and the glass transition temperature (T g ) of the cured epoxy matrix is increased.…”