JEC COMPOSITES MAGAZINE - Issue #88 - April 2014 - Special JEC Americas Spring Edition - 33

Fig. 3: Wide range of normalized stiffnesses E1* in C-Ply selection charts based
on 3 thick-thin starting C-Ply plies and 3 layup ratios, with off-axis angles from
20 degrees and up

Fig. 5: Selection of the best laminate from a given E6°/E1° value

Other laminate selection criteria than E1*
may be used, such as E6°/E1°, or E2°/E1°,
or the off-axis angle from the manufacturing and product availability standpoint, as
shown in Figure 5. It takes only a single option and the others will be locked in, with no
possibility to change. This strict and rigid order of laminate stiffness is discussed later in

Finally, these charts can be used to replace
existing laminates designed with the traditional black aluminium rules, so the high
productivity and quality of C-Ply can lead
to reduced weight and cost. Three typical
laminates are shown in Figure 6.
These laminates can be expressed in conventional designations shown alongside each

column in Figure 6. From these designations, it is easy to find their in-plane stiffness
in terms of E1* and E6°/E1° using the classical
laminated plate theory. The green letters in
the parentheses at the bottom of Figure 6
show the percentage of each ply angle in the
following order: (%[0], %[±45], %[90]).
The same master ply chart is used in Figure 7
to see if the 3 laminates with such a complex
stacking sequence can be replaced by the
laminates listed under the 9 groups of 3
thick-thin C-Ply and 3 layup ratios. It turned
out that Laminate A was the most difficult to
replace because of its high shear modulus.
The right side of Figure 7 shows how well
the replacement laminate can match the
original Laminate A. The shear modulus
match was good but the longitudinal stiffness was lower. The replacements for Lami-

Fig. 6: Three typical laminates having many 10-,
9- and 8-ply sub-laminates with a very complex
stacking sequence

No88 April 2014 /

Special JEC Americas 2014

this paper. It is to our
advantage to recognize
that these stiffness
and angle interactions
are predetermined
and can make design
and testing simple. It
is no longer correct
to assume that with 4
stiffness and 5 material
strength parameters
and dozens of options in lamination,
Fig. 4: Selection of the best laminate based on a required longitudinal
stiffness E1*
laminate selection will
be without limit. As
it turns out, there is only one option. This is
ing potential solutions. From left to right,
like metals. When selecting an aluminium
the off-axis angles are 22, 31, 26, 46 and 35
alloy, all the stiffness, strength and other
degrees. The best solution is shown with
properties are locked in. As seen before, if
the solid red dot for 4 reasons: 1) use of
the starting C-Ply thickness and the layup rathin-thin C-Ply (easier to homogenize); 2)
tio are known, there is only one option left:
use of a 2:0 layup ratio (1-axis layup with
either E1*, or E6°/E1°, or the off-axis angle.
significantly higher speed than 2-axis); 3)
off-axis angle of 46 degrees (lower cost CFigure 5 shows the results obtained with
Ply than with a shallower angle such as 31);
E6°/E1° = 0.3 as the initial choice.
4) reasonably high shear stiffness based on
In this case, there are also 5 possible lamiE6°/E1° = 0.26. To round off these off-axis
angles to something more comfortable, the
nates. The 34-degree one was selected as the
curves in Figure 4 can be used to determine
best laminate due to its 1-axis layup (highest
the effect of the rounding off.
productivity) and the highest E1* (0.46).

jec composites magazine 33

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

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #88 - April 2014 - Special JEC Americas Spring Edition