See figure 14-23.
Drawings specify ply stacking
angles and the sequence of the lay-up. A standard
laminate orientation code is used to ensure
standardization in the industry. The orientation code
denotes the angle, in degrees, between the fibers and
the X axis of the part. The X axis is usually
spanwise of the part, or in the direction of applied
loads. See figure 14-24. The laminate ply orientation
or stacking sequence is denoted in brackets, with the
angle of each ply separated by a slash (/); for example,
[+45/45/+45/-45]. Laminae are listed in sequence
from the first lamina to the last. The brackets or
parenthesis indicate the beginning and the end of a
code. The plus (+) and minus () angles are relative
to the X axis. Plus (+) signs are to the left of 0, and
minus () signs are to the right of 0. Adjacent laminae
of equal angles but opposite signs are identified as ±,
= +45, 45). The directional strengths and
stiffness of the laminate can be altered by changing
the ply orientation.
CATEGORIES OF COMPOSITE
Figure 14-23.Laminae stacking.
Advanced composite materials continue to be
increasingly popular with designers of new aircraft.
It is estimated that new airframes will be 75 percent to
Figure 14-24.Standard ply orientation clock.