Page 217 - 3D Fibre Reinforced Polymer Composites

206 30 Fibre Reinforced Polymer Composites

pinned composites is examined based on the limited amount of published data and
information. Included in this chapter is a description of the fabrication techniques, the
in-plane and through-thickness mechanical properties, and impact damage tolerance of
z-pinned composites. 3D sandwich composites manufactured using Z-fiberTM
technology is also briefly described.

9.2 FABRICATION OF Z-PINNED COMPOSITES

The manufacture of 3D composites with Z-fibersTM is a multi-stage process that can be
performed inside an autoclave or in a workshop using an ultrasonic tool. The fabrication
of z-pinned composites is similar to the manufacture of stitched composites in that the
through-thickness reinforcement is inserted as a separate processing step to create a 3D
composite material. In this way these reinforcement techniques are different to the
textile technologies of weaving, braiding and knitting that create an integrated 3D fibre
preform within a single stage process. The steps involved in z-pinning using the
autoclave process are shown schematically in Figure 9.2.

, VacuumBag

2-Fibre Preform
epreg Composite

Stage 1: Place 2-Fibre Preform on top of Prepreg and then
enclose in vacuum bag
(a)
Pressure
0

Stage 2: Standard cycle or debulk cycle, heat and pressure
compact preform foam, forcing the z-pins into the composite
(b)
Remove & Discard Foam

Cured 2-Pinned Composite

Stage 3: Remove compacted foam and discard. Finish with
cured z-pinned composite.
(c)
Figure 9.2 Schematic of the Z-fiberTM insertion process using an autoclave (Adapted
from Freitas et al., 1994)