Fiberwork materials


construction and dimensioning

targets of construction

 
  • design justiced to fibers, i.e. e.g. as big radii as possible in edges and areal parts instead of tube combines
  • high integration density, i.e. summary of monofunctional parts to one multifunctional part. By that the otherwise needed links between the separate parts become no longer necessary.


    • Depending on kind and use of a part the targets can be stiffness, strength and / or stability :
     
  • stiffness : in parts with a big area which are not essential in case of slip-up ( e.g. fairing parts )
  • strength : in parts which are essential in case of slip-up ( as e.g. the fork )
  • stability : stability problems are above all the snap of rods and the dent of sheets or bowls caused by high pressure forces in the plane of the part. This problem can get solved especially by optimizing of the form, e.g. fins with big volume in bowls ( this is how I´ve constructed the inner bodywork ).



    • procedure of calculation and dimensioning

      A calculation of fiberwork materials is possible very limited only, because "the" fiberwork material" does not exist in contrast to homogeneous materials such as alu or steel. Beside the fiber modules and the direction of the fibers you also have to consider the way and quality of processing and much more. With complexe parts as e.g. the inner bodywork of MagicScooter2 with in addition hard to define cases of load FEM-programmes only would be considered for calculation, which seemed to be much too lavish to me.
    Alternatively you can add results of experience as well as roughly estimated calculations. To understand the principle of supporting in complex parts resp. to localize their weak spots there´s also the possibility to build a prototype ( in case of small parts ) or a model and then to load them in an as practicable as possible way.
    In most parts the stiffness is authoritative. This calculation is much easier than the strength calculation. Here you have to trace the tension jumps from layer to layer, so you have to get through for every single layer.
    In the calculation of stiffness especially the fiber share of the whole laminate in a definite direction is important.


    General rules to define the laminate structure :

      Dimensioning at fiberwork materials doesn´t mean define the necessary thickness only, because "the" FWM doesn´t exist. It first has to get modelled depending on necessity with the following parameters :
  • kind of fiber ( material and weaving )
  • number of layers ( to get the necessary thickness for the chosen combination of parameters )
  • sequence of layers
    The single layer with the least danger of a break between the fibers ( the break takes place in the matrix resp. at the boundary layer matrix-fiber ) should be placed on the outside of the laminate ( so e.g. canvas outside and UD-layers inside )
    In addition the fabrics should get placed as regularly and symmetrically as possible in the laminate.
  • fiber directions
    Definite use of the anisotropy by placement of the fibers with a main part in main tension direction. As less secure you are about the direction of tensions as more you have to place the fibers "quasi-isotrop", i.e. distributed regularly in all directions.
    So-called "interlaminar tensions" on free laminate edges, so at holes, edges, force inlets, etc. can lead to a delamination of single layers. This danger can get lowered by a as low difference of fiber directions between the layers as possible, so e.g. not 2 UD-layers twisted 90° on top of each other.


    • general
    sandwich construction
    form building