Identifying the Problem



The lack of preferential anisotropic reinforcement in
“mainstream” composites has provided motivation
to develop materials with multidirectional strength
components.
Many multidirectional systems exhibit delamination
as a primary mode of failure.
Three-dimensional (3D) weaving solves both
problems--but so far the composite manufacturer and
weaver don’t fully communicate each other’s needs.
Traditional 2D Weaving
warp
fill
fabric
formation
zone
fabric flow
heddle eye
warp ends
warp
filling insertion
(through shed)
harness movement
filling
Processing of 3D Woven
Preforms
warp ends
filling insertion
shed
weaver
warp
filling insertion
fabric movement
Typical 3D Woven Geometry
Preform Variables








fiber type (IM7, AS4)
yarn size (3k, 6k, 12k)
yarn distribution (%0°, %90°, %z)
weave construction, particularly the
placement of the weavers
(in-phase or out-of-phase)
yarn spacing (yarns per inch)
fabric weight (oz/yd2)
fiber volume fraction (Vf)
weave angle
Typical Constituents of 3D
Woven Preforms

Most commonly used are graphite tows, with
availability the limiting factor in many cases.
Fiber type
Density
Linear density
Tow crosssectional area
g/cm3
lb/in3
tex
lb/106 in
mm2
in2 x 10-4
IM7-12k
1.77
0.064
446
25.0
0.252
3.90
AS4-3k
1.79
0.065
211
11.8
0.117
1.82
AS4-6k
1.79
0.065
425
23.8
0.237
3.67
AS4-12k
1.79
0.065
857
48.0
0.486
7.54
Preform Input Parameters

Using fiber volume (Vf), thickness (t), ply percentages
(wt%) as inputs:
wt%1 wt%2
wt%n 
w 

Vf =
 

 ...
t  r
r
rn 
Here r is fiber density for each n fiber type and w is the preform areal density.

Yarn spacings needed for each ith system (warp, fill,
weaver) can then be found using the tow linear
density N:
yarns per inch  ypii 
wi
Ni
 cos i
Weave Angle Projection
1/ppil

t
Np / ppil
t an  =
t  ppil
Np
Determining Preform Thickness
Requirements

Tows required to meet thickness can be estimated
assuming a common aspect ratio (AR):
AR = b
a
a
d
b
A ab  a2AR
a=
a 
A

3.9  104 in 2
6
tows needed for thickness
A =d 1
4AR
AR
 .00455 in
6

total thickness
tow thickness

t
2a

0.100 inches
2  .00455 inches
 11 tows
3D Woven Preform Case Study
Two sample preforms were specified,
each with a 45°weave angle requested:
Param eter
%0° fiber
0° fiber type
%90° fiber
90° fiber type
%z fiber
z fiber type
thickness (inches)
Volum e fraction (%)
Sample 1 Sample 2
47
77
IM7-12k
IM7-12k
47
17
IM7-12k
IM7-12k
6
6
AS4-3k
AS4-6k
0.100
0.100
56
56
The preforms were procured from a weaver,
then evaluated based on the design methodology.
Example Calculations

Example Calculations for Sample 2, using IM7-12k
graphite tows for all inputs:
Fiber direction
% tows
directional areal
density
2
(oz/yd )
0°
77
57.23
90°
17
12.63
ttt
6
4.46
Total
100
74.32
0°:
ypi = 57.23
oz
yd
2
6

2
 yd 
 
 110.4 ypi
25.0 lbs 16 oz 36 in 
10 in
6

lb
2
90°:
 yd 
ypi = 12.63


 
 24.4 ypi
2
25.0 lbs 16 oz 36 in 
yd
z:

yd 2

ypi = 4.46



 cos  i = 7.9 ypi
2
25.0 lbs 16 oz 36 in 
yd
oz
oz
10 in
10 6 in
lb
lb
Applying the Methodology
Sample 1
Param eter
0°
90°
ttt
Requir ed
Reported
Requir ed
Reported
Requir ed
Reported
areal weight
(oz/yd2)
34.9
34.9
34.9
34.9
4.5
4.5
yarns per inch
67.5
67.5
67.5
67
18.2
16
Volum e fraction
26.4
22.9
26.4
22.9
3.3
2.9
Sample 2
Param eter
0°
90°
ttt
Requir ed
Reported
Requir ed
Reported
Requir ed
Reported
areal weight
(oz/yd2)
57.2
12.5
12.6
57.2
4.5
4.5
yarns per inch
110.4
24
24.4
110
8.3
6
Volum e fraction
43.2
7.5
9.4
34.6
3.3
2.7
Measuring the Weave Angle
9°
Sample
Measured angle
Predicted angle
1
9.0°
14.4°
2
22.5°
22.7°
22.5 °
Examining Volume Fraction from
Input Parameters

Evaluating Sample 2:

yd 2

6 ypi = wz 2 


 cos22.5


11.8
lbs
16
oz
36
in
yd
oz
106 in
lb
w = 1.59+57.22+12.45 = 71.26 oz/yd2
36 in2 16 oz
oz
 
Vf  .064 3  .100 in 
 71.26 2
 yd 
lb
in
yd
lbs
Vf = 53.7%
It was calculated that 74.3 oz/yd2 was needed
to meet the 56% volume fraction specified
Conclusions



The methodology has been developed for crossdisciplinary understanding of the key variables in
3D weaving
Standardization and increased use of 3D woven
preforms should increase the communication
between weaver and customer
The key for both sides:
Understanding each other’s capabilities and
limitations