TM 1-1500-204-23-11
Figure 5-9. Fiber Orientations
(5) Positive and Negative Angles. Positive
respect to the laminate 0 degree iber direction (igure
angles are deined as being counter-clockwise from
the 0 degree iber direction when looking down on
the layup tool surface. Negative angles are clockwise
from the 0 degree iber direction. Not all aircraft
manufacturers use this convention during fabrication
of parts. Use this convention for deining positive
and negative angles unless otherwise speciied by
the system speciic technical manual. A -45 degree
ply and a +60 degree ply are shown in igure 5-9,
View B and View C.
(6) Woven Material Ply Angles. The construc-
tion of many plain weave fabrics eliminates the need
for 90 degree ply designations as well as positive or
negative ply designations such as "+45 or -45". For
example, the dry woven carbon cloth materials spec-
iied for repair patches in Chapter 7 of this manual
(SGP 196-P) has eleven 6k yarns per inch in the
warp direction, and eleven 6k yarns per inch run-
ning in the ill direction. The result is a fabric which
has essentially the same strength in both the warp
and ill directions. In this case, it is unnecessary
to differentiate a 0 ply from a 90 ply since they re
Figure 5-10. Typical Laminate
essentially the same. Likewise, it is unnecessary to
differentiate a +45 ply from a -45 ply. In laminates
e. Lamination. During the lamination process, it is
made exclusively from these materials, it is common
essential that the correct ply orientation and stacking
to see only "0" and "45", or "0/90", "45" to denote
sequence be maintained.
the ply orientations. When the laminate is made from
a combination of woven fabric and unidirectional tape
it is common to see a lowercase "w" or "f" after the
(1) Ply Orientation Tolerance. Typical repair
ply orientation to distinguish that ply as being woven
tolerance for ply alignment is 3. A ply misorientation
fabric as opposed to unidirectional tape.
of 5 can result in a 20% reduction in strength while
a 10 misorientation can result in as much as a 50%
(7) Laminate. A laminate is made up of several
reduction in strength. The system speciic technical
manual will list the required ply orientation tolerance.
laminas (plies) oriented in different directions with
