The geometry of the component, previously defined in mandrel generation, determines the stable paths that the user will be able to achieve. The main requirement of the fibre path, when determining its trajectory, is that it should not slip. This is accomplished within CADFIL in two ways.
In the first method, the fibre path follows a geodesic path, this being the shortest distance between two points on the mandrel. The limitation of this method of fibre path generation is however, that once the initial conditions of start position and start angle have been input, the rest of the path is uniquely defined by the geometry of the component. Therefore, the scope for attaining an optimum winding pattern for mechanical and environmental requirements can be limited.
The second method of path generation makes use of the frictional effects between fibre, resin and mandrel surface, to allow the fibre to be deviated away from the geodesic non-slip path, to a friction sustained non-slip path .
The amount of deviation from the geodesic path is dependent upon the friction coefficient, this being dependent upon the mandrel finish, fibre and resin type, etc., and also upon the geometry of the component. A higher local curvature will increase the normal reaction to the component surface, this in turn increases the frictional forces available to sustain the fibre on the required path, and hence the fibre path will deviate faster.
The CADFIL system can make use of both of these methods whilst a fibre path is being generated, the operator deciding upon the amount of friction to be applied, and when to use it.