Fiberwork materials

General

What do you understand by fiberwork materials
  A fiberwork material(FWM) comes into being by putting together several materials including a fiber material. In this case it´s high solid fibers in form of glass, carbon or aramid as well as a matrix in form of epoxy resin.


How I got to FWM ?

  As a carpenter I already had substantial contact to a fiber material, so I knew a lot about dealing with anisotropic material. Moreover I´ve been reluctant to use metalic materials because of the arduous work on it for lack of proper machines, but I nevertheless wanted to build a fully faired bike without outside help. For lack of alternatives I acquired the necessary knowledge from literature and experiments without much bother.


What are the advantages of fiberwork materials ?

 
  • high strength and stiffness with regard to weight
    stiffness strength

    The good qualities in fiber direction are fully utilizable just in pure oneaxle use, e.g. tension bars, bending beams, etc. Most disadvantageous case of a construction ( regarding low weight ) is the quasi-isotropic laminate ( in all directions of the laminate plane the same material qualities by the arrangement of the fibers in many different directions ).
    The more UD ( unidirektional fabric with fibers only in one direction ) you use therefore, the bigger is the potential to low weight.
  • more freedom in design
  • good qualities in suspension
  • high resistance against corrosion
  • low heat stretching


    • What are the disadvantages of fiberwork materials ?

     
  • strong anisotropy
    In contrast to an isotropic material (e.g. alu) with the same qualities ( strength, E-module, etc.) in all directions, there´s a big difference in fiberwork materials in this regard. The fibers support just in fiber direction.
    But this is a disadvantage just if you fight against this quality instead of making use of it determined.
  • high costs for material and work
  • complex process of construction
  • difficult processing
  • problems in designing of the introductions of forces


    • Kinds of fiber:

     
  • glass
  • carbon
  • aramid (kevlar)


    • Here the comparison of qualities to aluminium :
    comparison of qualities

    There´s also the possibility to combinate several kinds of fiber in one laminate :

     

    regarding CF alone

    regarding AF alone

    regarding GF alone

    CF / AF

    better blow toughness

    higher
    pressure strength

     

    CF / GF

    better blow toughness

     

    lower weight
    higher E-module

    AF / GF

     

    higher
    pressure strength

    lower weight
    higher E-module


    CF=carbonfiberplastic     AF=aramidfiberplastic     GF=glassfiberplastic

    I´d like to add to the kevlarfiber that its processing is much more difficult (e.g. with microgeared scissors). In addition kevlar gets unsightly under the influence of UV light and therefore it shouldn´t be used in the outer layer, also because in crashes or other injuries the surface gets rough resp."crumbly" and for that the repair is very difficult.


    kinds of weaving :

      In fabrics the threads cross right-angled (string and shot). The kind of crossing is called weaving and sets clearly the qualities of the fabrics.
  • canvas weaving : firm against thread shifts ( in processing ), but above all disadvantageous under demand on pressure because of the hard bent threads, and in addition it is very bad to shape.
  • köper weaving : good to shape
  • atlas weaving : very good to shape, but bad against thread shifts in process. These shifts can lower the performance.


    • The matrix :

      The matrix has to hold the fibers in form and its contribution to stiffness is just marginal. The forces mainly get transmitted into the fibers.
    I´ve used the cold hardening system of resin L and hardener L from R&G in all parts, which has an even sufficient time to process of 40 minutes. Other systems are either too expensive, have a too short time to process or they need heat for hardening.


    construction and dimensioning
    sandwich construction
    form building