JEC COMPOSITES MAGAZINE - Issue #88 - April 2014 - Special JEC Americas Spring Edition - 32

C-Ply

the tape edge is one-ply thick as compared
with the traditional triax that is two-ply
thick. These seams will be staggered as sublaminate tape is laid and stacked. The paper
by Nettles and Tsai in this volume describes
the effects of staggered seams.
If the starting ply is 50 gsm, each bi-angle
C-Ply will be 100 gsm and the 4-ply sublaminate will be 200 gsm. It was found that
the laminate would be sufficiently homogenized with as few as 4 such sub-laminates,
or a total of 16 plies or 800 gsm. Supporting
data is also provided in the article by Nettles
and Tsai.
When a laminate is homogenized, it can be
laid up without mid-plane symmetry and
thermal warpage is minimal. Such asymmetric or non-stop layup is faster and less
prone to error. By comparison, unitape
is too thick (150 versus 50 for NCF) and
takes 3 or 4 directions to lay the laminate;
i.e., 1 along the 0- and/or 90 axis, 2 along
the off-axis. The off-axis layup takes much
longer than the layup time for those along
the 0 or 90 degree axis. It is nearly impossible to build a laminate with 6 ply angles using unitape. The sub-laminate would be too
thick to be homogenized. One motivation
to have more than 4 ply angles is to reduce
the angle between plies, say, from 45 to 30.
Smaller interlaminar angles increase delamination and impact resistance. We will show
that with C-Ply, having 6 angles can be as
economical as when having fewer angles.
Using a 1- and 2-axis orthogonal layup can
also reduce scrap while increasing the speed
and productivity of ATL. A factor of 2 to
over 10 is possible depending on the aspect
ratio of the part. The 1-axis layup, that has
a ratio of 2:0 for C-Ply, will be the fastest.
For a 2:2 layup, it is more than twice as fast
as 4-axis unitape. For a 4:2 layup, it would
be between 2:0 and 2:2 because there will
be four courses of layup along the x axis as
compared with two courses along the y axis.
The basic bi-angle C-Ply can be used to
produce different combinations of tri-angle
C-Ply of [0/j/0/-j] with 1-axis layup, and
[0/±j/±y/90] with 2-axis layup. Thus,

Tab. 1: Nine varieties of laminates that can be generated from bi-angle
C-Ply with 3 thick-thin combinations and 3 layup ratios. Off-axis angles can be 45, 30 or any
value ± 20

Starting
C-ply

[0/j2] - Thin-Thick
(33/67/0) - 150 gsm

[0/j2] - Thin-Thick
(50/50/0) - 100 gsm

[0/j2] - Thin-Thick
(67/33/0) - 150 gsm

1-axis
2:0

[0/±j]2
=[p/3]2 for j=60
(33/67/0)

[02/±j]
(50/50/0)

[04/±j]
(67/33/0)

2-axis
4:2

[0/±j]2/(±y/90)]2
y=90-j
(22/67/11)

[(02/±j)2/±y2/902]
y=90-j
(33/50/17)

[(04/±j)2/±y2/902]
y=90-j
(44/33/22)

[0/±j/±y/90]2
= [p/6]2 for j=30

[02/±j/±y/902]
= [p/4]2 for j=45

[04/±j/±y/904]
y=90-j
(33/33/33)

2-axis
2:2

(17/66/17)

(25/50/25)

C-Ply can generate a much greater variety of
laminates arranged in 9 groups: 3 columns
of thick-thin bi-angle C-Ply, and 3 rows
of layup ratios as shown in Table 1 above,
where examples of off-axis angles of 30, 45
and 60 degrees are cited for their quasiisotropic cases.
Table 1 shows 9 possible laminates that can
be generated from 3 layup ratios along the
x and y axis. The layup ratios shown are
limited to 2:0, 2:2 and 4:2. They are selected
because of their high-speed productivity.
Ratios higher than 4:2 would certainly be
possible but would make homogenization more difficult to reach. Also shown in
parenthesis is the laminate designation as
the percentage of the 0, ±off-axis and 90
degree plies. For [0/45] C-Ply, there is only
one off-axis of 45, while for [0/30] there are
two at 30 and 60 degrees. But the percentages of off-axis plies are the same for all biangle C-Ply laminates with one off-axis ply.
We represent thick by assigning 2 plies to
designate thick plies; [0/452] meaning thin
0 and thick 45. Thus for each starting biangle C-Ply, we have 9 combinations, from
3 thick-thin multiplied by 3 layup ratios.
The same 9 possible laminate compositions
are also shown in the traditional carpet
plot in Figure 2. The percentage of [0] can
range from 16 to 67%, or 1/6 to 2/3. The
same range applies for off-axis ply angles, i.e.
[±j]+[±y]. The 1-axis layup is highlighted
in orange because of its high productivity
(by one order of magnitude with high aspect ratio) and high quality (easy nesting).

32 jec composites magazine / No88 April 2014

Fig. 2: Laminates generated from C-Ply with 1-axis
layup for three thick-thin combinations, in orange
circles, and 2-axis layup in dark blue circles. Not
included in the range of property variations are the
values of off-axis plies, that can range from shallow
angles as low as 20 degrees and up

Master design chart
With these variations, the normalized inplane stiffness component E1* is shown for
all 9 combinations in Table 1, where 3 thickthin bi-angle starting C-Ply plies are shown
on the top row, each with 3 layup ratios. The
E6°/E1° value as a function of the off-axis
angle is also shown for each case.
It is a new strategy to use the off-axis angle
as a design variable. C-Ply manufacturing
is designed to use this angle variable. The
familiar [π/4] as well as [π/3] and [π/6] are
also shown as reference points.
As an example for the selection of laminates,
let us assume that we want the longitudinal
stiffness E1* at a normalized value of 0.5,
for which a horizontal red line is drawn in
Figure 4.
There are 5 intersections with the stiffness
lines shown by red vertical lines represent-
JEC COMPOSITES MAGAZINE - Issue #88 - April 2014 - Special JEC Americas Spring Edition

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