Tailored fiber placement

Fiber rovings are placed in an optimal way, when their orientation is parallel to the principal stress direction. This tailored fiber placement can be achieved with CAIO software (Computer Aided Internal Optimization). CAIO integrates the direction field of principal stresses and places the principal stress lines (fiber rovings) 'infinitely dense'. A special fiber course with a special density can be extracted by mouse click from this continuous distribution.
Fig. 1: Extracting fiber rovings from a continuous fiber field of the 1st principal stress
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Fig. 2: Principal stress lines and direction field (detail from Fig. 1)
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Extracted fiber rovings (blue) and vectors of the 1st principal stress direction (black).  Fiber rovings follow the direction field. There are regions with a change of sign. CAIOShell integrates correctly over these regions without reversal of the direction.

Special fiber placement can be achieved by interactive postprocessing. Normally, the computed CAIO- pattern is subjected to different constructive changes. E.g., the surface weight may change or a roving concentration is requested due to high local stresses. Repetitive computations are avoided due to the fact, that all possible fiber courses were already computed and saved by the preliminary step with CAIOShell. The final fiber placement is done by interactive manipulations within Tecplot®. The user extracts a subset of rovings from the dense fiber field and optionally manipulates a single fiber by moving this item with the mouse device.

Within the postprocessor users can perform the following tasks:

  1. Extraction of an arbitrary number of fibers (rovings). This is done by an internal interpolation on the dense fiber field.
  2. Additional adding or deleting of fibers from the discrete fiber field. 
  3. Afterwards, user can move single fibers, forcing the fiber to remain on the 3D-shell surface. 
  4. Cutting single fibers or fiber regions.
  5. Calculation of the relative thickness of the fiber field. (Thickness will change due to the 'flowing' character of the fiber course.)
  6. Extraction of fiber position (x,y,z- coordinates, ASCII-format).
  7. Development of curved fiber courses to a plane, as long as this is possible. 
Fig. 3: Interactive fiber management (Point 1-3)
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Fig. 4: Fiber management (Point 7): Developed cone
This conical shell is an example of a developed surface. The structure shown under wind load is characterized mainly by membrane stresses. After optimization the CAIO-pattern can be developed. All Tecplot®- features (change of fiber density, manipulation of single fibers) are immediately effective on the developed plane.