Indian Journal of Fibre & Textile Research
Vol. 33, December 2008, pp. 411-418
Effect of punch density, depth of needle penetration and mass per unit area on
compressional behaviour of jute needle-punched nonwoven fabrics using central
composite rotatable experimental design
Surajit Senguptaa
National Institute of Research on Jute and Allied Fibre Technology, 12 Regent Park, Kolkata 700 040, India
Prabir Ray
Institute of Jute Technology, 35 Ballygunge Circular Road, Kolkata 700 019, India
and
Prabal Kumar Majumdar
Government College of Engineering and Textile Technology, Serampore, Hooghly 712 201, India
Received 4 October 2007; revised received and accepted 5 February 2008
The compressional behaviour of jute needle-punched nonwoven fabric has been studied. Statistical models using
central composite rotatable experimental design are developed on compression parameter, recovery parameter, energy loss
and thickness loss, depending on the three important parameters of needled fabric, i.e. needling density, depth of needle
penetration and mass per unit area. From this model and its contour diagrams, the effects of different parameters can be
understood and prediction of compressional behaviour can be made knowing the values of independent parameters. The
correlation coefficients between observed and predicted values are found to be significant in all the cases. It is found that the
15-16 mm depth of needle penetration, 170-180 punches/cm2 needling density and 800-900 g/m2 mass per unit area is a very
critical combination which might be considered for minimum compressibility because the deviation from any of the variable
may be responsible for the increase in compressional behaviour.
Keywords: Central composite rotatable experimental design, Compressional parameter, Energy loss, Jute, Needle-punched
nonwoven, Recovery parameter, Thickness loss
IPC Code: Int. Cl.8 D04H
1 Introduction
Needle-punched nonwoven fabric is a sheet of
fibres made by mechanical entanglement, penetrating
barbed needles into a fibrous mat.1 Such fabric is
extensively used in technical applications. In such
applications, fabric is subjected to normal
compressive loads, and the physical, tensile and
hydraulic properties change with these loads,
depending on the compressional behaviour of the
fabric. The nonwoven geotextile, when used
underground, is subjected to compressional loads,
both static and dynamic. A number of papers have
been published on tensile2,3, hydralic4,5 and
compressional behaviour6-8 of nonwoven geotextiles.
Some work has been reported on the compressional
behaviour of loose fibre masses.9,10
_____________
a
To whom all the correspondence should be addressed.
E-mail: [email protected]
Jute dominated the world market as packaging
material, carpet backing and industrial textiles till the
synthetic material came into competition. In search of
diversified uses of this fibre, successful attempts have
been made to use this natural and ecofriendly
technical fibre in the field of geotextile, floor covering
and filtration.11,12 Punch density, depth of needle
penetration and mass per unit area of jute needlepunched nonwoven are the parameters, which have
significant effect on compression.13 The effect of
these parameters on the properties of nonwoven has
been reported in number of papers.14-16 But the
detailed work has not been reported so far regarding
the effect of these parameters on compressional
behaviour of jute needle-punched nonwoven. In this
study, an attempt has been made to understand the
effect of punch density, depth of needle penetration
and mass per unit area on compression, recovery,
energy loss and thickness loss of jute needle-punched
nonwoven geotextiles.
412
INDIAN J. FIBRE TEXT. RES., DECEMBER 2008
2 Materials and Methods
Table 1―Actual and coded values of different factors
2.1 Materials
Tossa jute of grade TD3 (ref. 17) was used to
prepare needle-punched nonwoven fabric, having the
fibre properties: linear density, 2.08 tex; tenacity,
32.30 cN/tex; and extension-at-break, 1.60%.
2.2 Methods
The significant independent variables of jute
needle-punched nonwoven with respect to different
properties, namely needling density, depth of needle
penetration and mass per unit area, were identified.18
The useful limits of the three variables stated above
were selected based on the information available in
literatures14-16 and also by conducting a number of
preliminary experiments. The limits, and actual &
coded values of different factors are given in Table 1.
2.2.1 Developing the Design Matrix
To determine the effects of factors (variables) on
the response parameter, it was decided to use the
statistical technique called central composite surface
design to develop the design matrix. The matrix so
developed was a 20 point central composite design
which consists of a full factorial design 23 (8) plus 6
centre points and 6 star points.19 The 20 experimental
runs thus allowed the estimation of the linear,
quadratic and two-way interactive effects of the
various factors on properties. The design matrix so
developed with coded values of the factors is given in
Table 2.
2.2.2 Fabric Preparation
Jute reed was subjected to softening treatment with
4% jute batching oil-in-water emulsion and then
processed in a breaker card. To make jute needlepunched nonwoven, the breaker card sliver was fed to
Dilo nonwoven plant comprising a roller and clearer
card, a camel back cross-lapper and needle loom
(Model number OD II/6). Twenty samples as per the
design matrix (Table 2) were prepared using five
levels of punch density, depth of needle penetration
and mass per unit area.
2.2.3 Measurement of Compressional Behaviour
The compression and recovery between 0 kPa and
200 kPa were measured on Instron tensile tester
(Model No. 5567). The gauge length between
stationary anvil and pressure foot was set at 0 mm.
The needle-punched nonwoven sample was placed
between 150 mm diameter stationary anvil and
Factor
-1.682
-1
70
106.5
18
300
Punch density (X1)
punches/cm2
Depth of needle
penetration (X2), mm
Mass per unit area
(X3), g/cm2
Code
0
+1
+1.682
160
213.5
250
16.4
14
11.6
10
442
650
858
1000
Table 2―Constructional details of experimental fabrics
Sample Experimental
No.
run order
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
4
11
9
15
2
10
3
7
17
1
16
19
13
20
5
18
6
14
12
8
Needling
density
punches/cm2
1
-1
1
-1
1
–1
1
-1
1.682
-1.682
0
0
0
0
0
0
0
0
0
0
Depth of Mass per
unit area
needle
g/m2
penetration
mm
1
1
-1
-1
1
1
-1
-1
0
0
1.682
-1.682
0
0
0
0
0
0
0
0
1
1
1
1
-1
-1
-1
-1
0
0
0
0
1.682
-1.682
0
0
0
0
0
0
150 mm diameter pressure foot, which are well
separated in the start of experiment. Then the pressure
foot started moving downward at a speed of 2 mm per
min. After reaching the maximum compressional load
of 3532 N (exerts pressure of about 200 kPa), the
pressure foot automatically started moving up with
the same speed (2 mm/min), decreasing the load
accordingly. A diagram, plotting the compressional
load against thickness (Fig. 1), was available along
with a report of compressional deformation at a
required compressional load. Average of ten such
diagrams was considered here.
The initial thickness, compressed thickness and
recovered/final thickness were available from this
graph. Compressional parameter (α) and recovery
parameter (β) were calculated from the best fit
equations as suggested by Sengupta et al. 6,7, 13 For
jute needle-punched fabrics, the following equations
SENGUPTA et al. : COMPRESSIONAL BEHAVIOUR OF JUTE NEEDLE-PUNCHED NONWOVEN FABRICS
are found to be best fit in describing the compression
and recovery behaviour:
T/T0 = 1 – α / log e (P/P0)
T /Tf = (P/Pf)-β
Compression:
Recovery:
where T0 and Tf are the initial and the final thicknesses
at initial and final pressures P0 and Pf respectively;
and T, the thickness at any pressure P. In the above
equations, α and β are the dimensionless constants
indicating the compression and recovery parameters
of the fabric respectively.
The per cent energy loss (EL) during compression
and recovery can be calculated as follows:
EL (%) = [(E1 – E2)/ E1 ] × 100
413
where E1 is the potential energy stored during
compression; and E2, the energy recovered during
recovery. These energies were measured as the area
under the compression or recovery curves from
Instron tester.
The per cent loss in thickness (TL) during
compression and recovery is obtained by the
following relationship:
TL (%) = [(T0 –TF)/T0] × 100
where TF is the thickness after recovery or final
thickness. All these data are shown in Table 3.
2.2.4 Development of Statistical Model
Proposed Polynomial
To correlate the effects of factors and the response,
the following second order standard polynomial was
considered20:
y = b0 + b1 x1 + b2 x2 + b3 x3 + b11 x12 + b22 x22
+ b33 x32 + b12 x1 x2 + b13 x1 x3 + b23 x2 x3
… (1)
where y represents the response and b0, b1, b2,
………,b23 are the coefficients of the model.
Evaluation of Coefficients of Model
Fig. 1―A typical experimental pressure-thickness curve of a jute
needle-punched nonwoven fabric
The coefficients of main and interaction effects
were determined by using the standard method.21
Table 3―Various parameters expressing the compressional behaviour
Sample
number
Initial
thickness
mm
Compressed
thickness
mm
Final thickness
mm
Compressional
parameter
(α)
Recovery
parameter
(β)
Energy
loss
%
Thickness
loss
%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
7.550
8.815
5.152
5.795
5.315
7.195
4.967
5.505
8.023
5.690
7.395
5.120
4.525
6.880
5.821
4.737
5.392
5.562
4.468
5.439
1.372
2.371
1.465
2.088
0.424
1.623
1.273
1.590
1.212
2.098
0.926
1.628
0.710
2.880
1.869
1.992
1.899
1.491
1.998
1.229
4.291
5.829
3.152
3.827
2.957
4.380
3.015
3.681
4.704
3.524
3.615
3.263
2.284
4.687
2.573
3.521
2.649
3.406
3.047
3.844
0.107655
0.096176
0.094153
0.084160
0.121068
0.101886
0.097845
0.093564
0.111689
0.083054
0.115089
0.089730
0.110920
0.076490
0.089320
0.076238
0.085228
0.096295
0.072731
0.101835
0.150015
0.118345
0.100801
0.079711
0.255522
0.130612
0.113437
0.110441
0.178418
0.068230
0.179186
0.091475
0.153721
0.064072
0.042057
0.074939
0.043791
0.108683
0.055521
0.150023
67.72
70.88
74.77
74.12
68.61
71.86
74.09
76.68
73.99
78.24
73.86
73.13
76.73
76.48
76.18
77.55
78.47
75.86
76.63
78.21
43.17
33.87
38.82
33.96
44.36
39.12
39.30
33.13
41.37
38.07
51.12
36.27
49.52
31.87
55.80
25.67
50.87
38.76
31.80
29.32
INDIAN J. FIBRE TEXT. RES., DECEMBER 2008
414
Table 4 shows the regression coefficients of the
proposed model for different parameters.
Correlation between Observed and Calculated Values
The correlation coefficients between the observed
values and the predicted values by proposed model
are shown in Table 5. It shows a very good
correlation.
Checking the Adequacy of Models
The analysis of variance (ANOVA) technique was
used to check the adequacy of the developed models.
The ANOVA results of proposed model are given in
Table 6. Accordingly F-ratios of the developed
models were calculated for 95% level of confidence
and were compared with the corresponding tabulated
values. If the calculated values of F-ratio did not
exceed the corresponding tabulated value then the
models were considered adequate. The tabulated
value of F-ratio at 95% confidence level is 5.05. For
this purpose the F-ratio is defined as follows:
good correlation (Table 5). The values of the
calculated correlation coefficient are much higher in
all the cases than the standard value of correlation
coefficient (i.e. 0.444) at 5% level and 18 degree of
freedom.22 It indicates that the observed values of
needle-punched nonwoven has a real degree of
association with the predicted values of the fabric.
The significance of the effect of the variables was
tested by F-ratios (Table 6). These quadratic
equations were also used to arrive at possible
combinations for each assessment and the respective
response using these values. The contour diagrams
were plotted to study the effect of variables on the
responses (Figs 2 – 5).
The regression coefficients have a value either
positive or negative and accordingly have an effect on
the experimental results. For a variable to have a
significant effect, its coefficient must be greater than
twice the standard error. However, the non-significant
coefficients should not be eliminated altogether.
The effects of variables or interaction of variables
on compressional parameter (α), recovery parameter
F-ratio = Lack of fit (mean square) / Error (mean square)
3 Results and Discussion
Table 3 shows the values of dependable
parameters, i.e. compressional parameter (α),
recovery parameter (β), energy loss (EL) and thickness
loss (TL), obtained from the compression testing. To
establish the relationships between the independent
and the dependent variables, regression analysis was
done. The regression coefficients (Table 4) were used
in the quadratic Eq. (1) for the determination of
predicted response values. The correlation
coefficients between the observed values and the
predicted values by proposed model illustrate a very
Table 5―Correlation coefficients between the observed values
and the predicted values by proposed model
Parameter
Calculated Correlation
correlation coefficient at
coefficient 5% level and
18 degree of
freedom22
Compressional parameter (α)
Recovery parameter (β)
Energy loss (EL)
Thickness loss (TL)
0.86
0.84
0.77
0.90
0.444
0.444
0.444
0.444
Remark
Significant
Significant
Significant
Significant
Table 6―ANOVA of the proposed model
Parameters 1st order
term
2nd order Lack of fit
term
Error
F-ratio
5
-
Table 4―Regression coefficients of model
Coefficient
α
β
EL
TL
b0
b1
b2
b3
b11
b22
b33
b12
b13
b23
0.086907
-0.001167
-0.007301
-0.007530
0.003914
0.005696
0.002618
-0.000753
-0.000249
0.002048
0.078936
-0.001770
-0.029115
-0.024269
0.017134
0.021378
0.012033
-0.009301
-0.009393
0.016562
75.91440
0.79709
1.41892
0.58064
-0.53518
-1.46297
-0.36170
0.00177
0.41545
-0.55932
38.81235
0.04024
-2.94973
-4.04492
-0.34141
1.06393
0.00587
-0.84963
0.34307
0.43833
α – Compressional parameter, β – Recovery parameter, EL –
Energy loss, and TL –Thickness loss.
d.f.
α
3
6
5
SS
MS
0.001521 0.000826 0.000619 0.000634
0.001521 0.000826 0.000124 0.000127
0.976
SS
MS
0.019664 0.016497 0.011133 0.009097
0.019664 0.016497 0.002227 0.001819
1.224
SS
MS
40.7768
40.7768
40.7406
40.7406
62.7683
12.5537
27.0074
5.4015
2.324
SS
MS
342.2940
342.2940
26.2470
26.2470
83.4060 745.7100
16.6812 149.1419
0.112
β
EL
TL
d.f.— Degree of freedom; SS— Sum square, and MS— Mean
square.
SENGUPTA et al. : COMPRESSIONAL BEHAVIOUR OF JUTE NEEDLE-PUNCHED NONWOVEN FABRICS
(β), energy loss (%) and thickness loss (%) can
effectively be interpreted and explained by regression
coefficients and contours. The information available
from contour diagrams regarding the interactions of
parameters on compressional behaviour is very much
useful to design a jute needle-punched nonwoven for
various applications.
415
3.1 Compressional Parameter
Figure 2a shows the contour diagram of
compressional parameter (α) of jute needle- punched
nonwoven with respect to the workable range of
needling density and depth of needle penetration for
mass per unit area of 500 g/m2. Similarly, Fig. 2b
shows contour diagram of α with respect to mass per
unit area and needling density for depth of needle
penetration of 15 mm. Again, Fig. 2c shows the
contours of α with respect to mass per unit area and
depth of needle penetration for fabric with 198
punches/cm2. From these diagrams, it is observed that
with the increase in depth of needle penetration or
needling density or mass per unit area, α initially
decreases up to a minimum value and then it
increases. Higher the needling density or depth of
needle penetration, higher is the entanglement and
consolidation and hence α is decreased initially.
Beyond a certain value, the increase in above
parameters also increases α, which may be due to
fibre breakage in severe action of needles, resulting in
lower consolidation as suggested by Purdy.1 The same
phenomenon has been observed by other workers and
explained in similar way.14,15
Higher mass per unit area offers more number of
fibres to the needle barb to rearrange in vertical
direction, resulting in higher consolidation. Hence,
there is a decrease in α value. After a certain mass per
unit area, needle penetration is much difficult and the
fibre carrying capacity of the needle barb is reached to
maximum and chances of fibre breakage increases,
which causes lower consolidation and that is why
there is an increase in α value.
The center of minimum α is achieved using the
combination of depth of needle penetration, 15-16
mm; needling density, 170-180 punches/cm2 and mass
per unit area, 800-900 g/m2. A deviation in either side
of these combination results in the increase in
compressibility for jute needle-punched cross-laid
nonwoven fabric.
3.2 Recovery Parameter
Fig 2―Contours of compressional parameter (a) with mass per
unit area 500 g/m2, (b) with needle penetration 15 mm, and (c)
with needling density 198 punches/cm2
Contour diagrams of recovery parameter (β) with
respect to the workable range of needling density and
depth of needle penetration for mass per unit area of
500 g/m2, and of mass per unit area and needling
density for depth of needle penetration of 15 mm are
shown in Figs 3a and 3b. Similarly, Fig. 3c
demonstrates the effect of mass per unit area and
depth of needle penetration on β of fabric with 198
punches/cm2. It is observed from the figures that
416
INDIAN J. FIBRE TEXT. RES., DECEMBER 2008
β value decreases with the increase in needling
density, depth of needle penetration and mass per unit
area due to higher entanglement, resulting in more
compact fabric structure. In case of very high (240
punches/cm2) or very low (100 punches/cm2) needling
density, the increase in needle penetration above
15 mm or mass per unit area above 750 g/m2 shows
increase in β value due to lower consolidation
(Figs 3a and 3b). The minimum point is achieved
using the parameters, depth of needle penetration,
15-16 mm; needling density, 170 punches/cm2; and
mass per unit area, 800-900 g/m2.
Fig. 3―Contours of recovery parameter (a) with mass per unit
area 500 g/m2, (b) with needle penetration 15 mm, and (c) with
needling density 198 punches/cm2
Fig. 4―Contours of energy loss (a) with mass per unit area 500
g/m2, (b) with needle penetration 15 mm, and (c) with needling
density 198 punches/cm2
SENGUPTA et al. : COMPRESSIONAL BEHAVIOUR OF JUTE NEEDLE-PUNCHED NONWOVEN FABRICS
3.3 Energy Loss
Energy loss is basically the difference between the
energy stored during compression and energy gained
during recovery. Contour diagrams of energy loss due
to one complete compression-recovery cycle have
417
been shown in Figs 4a – 4c in different combinations
of needling density, depth of needle penetration and
mass per unit area. This effect basically depends on
the complicated and combined interaction of energy
gain by compression and energy loss by recovery. As
needling density is increased within the workable
range, energy loss always decreases. With the
increase in needle penetration, mass per unit area or
depth of needle penetration, the energy loss increases
due to more compact structure of fabric, which
requires higher energy to compress. In low mass per
unit area (around 400 g/m2), the increase in needling
density above 210 punches/cm2 or depth of needle
penetration above 15 mm shows decrease in energy
loss value (Figs 4b and 4c) due to lower consolidation
in structure.
3.4 Thickness Loss
Effect of needling density, depth of needle
penetration and mass per unit area on thickness loss
due to one compression-recovery cycle of jute needlepunched nonwoven fabric is shown in Figs 5a – 5c.
With the increase in any of these parameters, the
thickness loss always decreases. Thickness loss
denotes the difference between initial thickness and
final thickness after recovery. As any of these
parameters increases, the structure of fabric becomes
more compact. This resists compression and
facilitates recovery, resulting in lower thickness loss.
Figure 5a shows that the increase in needling density
for any depth of needle penetration has hardly any
effect on thickness loss.
Fig. 5―Contours of thickness loss (a) with mass per unit area 500
g/m2, (b) with needle penetration 15 mm, and (c) with needling
density 198 punches/cm2
4 Conclusions
4.1 Statistical models are developed relating the
compressional behaviour (compressional parameter or
recovery parameter or energy loss or thickness loss)
and three effective independent parameters, i.e.
needling density, depth of needle penetration and
mass per unit area of jute cross-laid needle-punched
nonwoven. From this model, one can understand the
effects of different parameters on compressional
behaviour and can also predict the compressional
behaviour approximately knowing the values of
factors or parameters.
4.2 The information available from contour
diagrams regarding the interactions of parameters on
compressional behaviour is very much useful to
design a jute needle-punched nonwoven for various
applications.
INDIAN J. FIBRE TEXT. RES., DECEMBER 2008
418
It is found that 15-16 mm depth of needle
penetration, 170-180 punches/cm2 needling density
and 800-900 g/m2 mass per unit area is a very critical
combination which might be considered for minimum
compressibility because deviation from any of the
variables may be responsible for the increase in
compressional behaviour.
4.4 In general, with the increase in needling density
or depth of needle penetration or mass per unit area,
compressional parameter decreases, recovery
parameter decreases, energy loss increases and
thickness loss decreases.
4.5 In case of high needling density (around 230
punches/cm2), the increase in mass per unit area
above 750 g/m2 or needle penetration above 15 mm
shows increase in both compressional and recovery
parameters.
2
4.6 In low mass per unit area (around 400 g/m ),
the increase in needling density above 210
punches/cm2 or depth of needle penetration above 15
mm shows decrease in energy loss value.
4.7 Increase in needling density for any depth of
needle penetration has hardly any effect on thickness
loss.
Industrial Importance: This study will be helpful in
designing the jute needle-punched nonwoven fabric
for better performance with respect to compressional
behaviour which is an important property for some
industrial uses.
4.3
Acknowledgement
One of the authors (SS) expresses his sincere
gratitude to Dr S K Bhattacharyya, Director, National
Institute of Research on Jute and Allied Fibre
Technology, Kolkata, for providing study leave to
carry out this work.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
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