The pipes
must be machine-made and the machines must be equipped with a control
system that guarantees close tolerances of the quantity and lay-out
of the reinforcements.
The filament winding process should be normally preferred.
There are two widely used filament winding processes:
• The cross filament winding in which the fibers are layed so
to form an angle against the pipe axis of ± 55 - 65°. In
this case the strength of the fibers is distributed in the hoop and
longitudinal directions according to the selected angle. When this
angle is 55° the distribution of the strength is 2 in the hoop
and 1 in the axial direction i.e. the same proportion as the stress.
