A Fibre-Path Generation Algorithm for Fibre-Steered Variable Stiffness Laminates

A Fibre-Path Generation Algorithm for Fibre-Steered Variable Stiffness Laminates

Hijne, Max (TU Delft Aerospace Engineering)

van Campen, J.M.J.F. (mentor)
Benedictus, R. (graduation committee)
Peeters, D.M.J. (graduation committee)
Bergsma, O.K. (graduation committee)

Delft University of Technology

Aerospace Engineering

2022-07-12

The development of novel materials has been of great interest to the aerospace industry in the pursuit of efficiency and cost reduction. Fibre-steered variable stiffness laminates have promising characteristics due to the ability to better tailor designs for expected loading, as the fibre orientation can be varied within a layer. This thesis was created to develop a fibre placement planning algorithm for fibre-steered layers on moderately curved open shells for a given fibre angle distribution.

The fibre-steered layers are to be produced by Automated Fibre Placement (AFP) without any course overlaps, which means that several manufacturing defects have to be considered. Gaps between courses are inevitable due to course shifting in combination with the prescribed fibre paths, and tow cuts run the risk of tow straightening due to loss of steering control of the AFP roller head. Furthermore, steering limits have to be observed to prevent tow buckling.

The thesis objective was approached by dividing it in three parts. Firstly, the geometry of the mould and the course paths was defined parametrically in the form of NURBS surfaces and curves. These have been widely used in Computer Aided Modelling (CAM) and have extensive support in terms of existing algorithms and documented work. Additionally, performing most operations in the parametric space allows for greater accuracy compared to general finite element methods.

Secondly, the fibre angle distribution was converted into a fibre layer. This was initiated by generating initial course centre lines, which were then fit onto the parametric surface. Representations of tow courses were made by geodesically offsetting the course centre lines in the binormal direction. A curve-curve intersection algorithm was then used to accurately detect tow overlaps, which were handled according to the tow placement strategy. Two tow placement strategies have been developed, one for general use and one to specifically prevent tow straightening. In addition, curvature of the course centre line was registered to check for tow buckling, and the minimum cut length was enforced by evaluating the length of tow segments.

Lastly, fitness criteria for fibre-steered layers were defined. Layers were evaluated for gap percentage, fibre angle error and number of cuts. These can be used to objectively grade layers against each other, or to assess the effects of fibre steering against conventional laminates.

Variable Stiffness
Composites
Fibre Steering
Automated Fibre Placement

http://resolver.tudelft.nl/uuid:114bd4e8-093e-4cb9-827f-c0641381f2ff

Student theses

master thesis

© 2022 Max Hijne