Page 71 - 3D Fibre Reinforced Polymer Composites

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3.7 COMPONENT QUALITY

There are a number of factors that can define the quality of the component produced via
a liquid moulding process. Factors such as adequate fibre volume fraction, correct fibre
orientation, degree of resin cure and interfacial bonding between the fibre and resin are
important but are generally controlled through the preform design, resin selection and
control over the cure cycle. The primary component quality factor that is a direct result
from the process of liquid moulding is the presence of defects such as voids, porosity or
dry patches within the component. A dry spot is defined as a region of the preform that
has not been wet out by resin, an example of which is shown in Figure 3.7a. Voids
(Figure 3.7b) are bubbles of air or other gases, whilst porosity is a collection of voids
within a region.

b)
Figure 3.7 a) Typical dry patch b) Typical void between reinforcement tows

Dry spots essentially occur due to the resin not flowing correctly to every part of the
preform. This can be due to a poor design of the resin inlet and outlet positions which is