2. Anisotropic Behaviour of Natural wood Palmyra (Borassus Aethiopum Mart) of Chad
http://www.iaeme.com/IJMET/index.asp 103 editor@iaeme.com
Key words: Borassus Aethiopum Mart, Wood, Anisotropic Material, Fiber,
Natural Composite.
Cite this Article: Ngargueudedjim K, Annouar D. M, G.E. Ntamack, S.
Charif D’ouazzane and Bianpambe H. W. Anisotropic Behaviour of Natural
wood Palmyra (Borassus Aethiopum Mart) of Chad, International Journal of
Mechanical Engineering and Technology, 6(9), 2015, pp. 102-111.
http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=6&IType=9
1. INTRODUCTION
The Palmyra is an angiosperm spermatophyte plant (class of monocotyledons) in the
class of palm. It grows in the African savannah [1]. He develops a trunk from 15m to
20m of length and 0.5m to 1.2m of diameter [2]. Its characteristics vary from one
region to another. Its wood has a woody tight structure, typical of palm trees, with
significant internal tensions [3, 4]. Unlike other woods whose heartwood (wood very
old and hard) is in the heart of the stem, Palmyras heartwood is located between
sapwood and bark. This wood rots hardly, even in water, and resistant to salinity. It is
not attacked by termites, marine borers and mushroom. It is an excellent lumber
which was widely used in civil engineering for the construction of bridges, wharves,
warehouses of infirmaries and in ports. Its fibrous structure and strength makes it a
material of choice carpentry and plastering. Finally, we note the recent use of this
wood in joinery and cabinet for manufacturing modern living rooms furniture, trunks
etc [1, 5, 6]. In Chad, we found plenty in the Sudano-Sahelian zone [7, 8]. In some
rapidly growing cities, It constitutes the frame of houses (walls supports, frames, door
and window frames, window frames). In rural areas, it is also widely used in
construction and as palisades support poles, in addition to many other domestic
purposes (manufacture beehives, seats, and shelters for domestic animals). Given its
importance in the construction work, knowledge of scientific data is essential to
define a strategy for the rational use. The work carried out concerning the extent of its
elastic constants as an orthotropic anisotropic material (natural composite).
Specifically, it is to determine its mechanical parameters which are the Young's
modulus, Poisson’s coefficients and shear modulus by using the 6 test method.
2. PLANT MATERIAL TESTING
The plant material is taken from a trunk of a male Palmyra tree aged of about 30
years. Its average height and bead diameter in the middle of the useful length (8m of
height) are respectively 16m and 34cm. The trunk is cut into pieces of 1.20m. The
piece of the base circumference of 1.46m is used for these experimental tests. The
sampling site is in the village Malfana at south of N'Djamena – Chad, located at
15°15.113 east longitude and 11°11.771 north latitude (figure 1).
Figure 1: Localization of Palmyra groves of the village Malfana.
3. Ngargueudedjim K, Annouar D. M, G.E. Ntamack, S. Charif D’ouazzane And Bianpambe H. W
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The average values of its chemical composition are 65.66% of cellulose, 23.66%
of lignin, 9.33% of hemicellulose and 1.35% of extractives. The density at 12% humidity is
823.22kg/m3
[9].
3. METHODOLOGY
3.1. Theoretical reminders
3.1.1. Anisotropy wood material
Wood is a natural composite material which is heterogeneous, porous anisotropic. It
has several levels of well organized cellulars structures and is made with 3 natural
biopolymers including:
- 2 amorphous polymers, lignin and hemicellulose which constitute the matrix,
- 1 crystalline polymer, cellulose which contributes to strengthening [10].
With the anisotropic material, the main directions of strain are not necessarily those
stress. In the case of a parallel or perpendicular effort to the direction of the fiber, the
two main directions are the same. It is possible to determine the Young’s modulus in
this direction and the corresponding Poisson's ratio with one strain gauge placed along
one of the two directions. If the force is neither parallel nor perpendicular to the fiber
direction the main directions of the strain are different from those of the stress and
those of the material. It takes this time a diagonal rosette (3 gauges at 45°) or Delta
rosette (3 gauges at 60°) for measuring strain. For an orthotropic material in plane
stresses or in the presence of an isotropic plane, it must necessarily the following five
parameters to calculate the stresses:
- Poisson’s coefficient III, Young’s modulus EI, EII and Coulomb’s modulus GI II,
which are independent,
- Poisson’s coefficient II I = I II * EII / EI if the material properties are the same in
tension and compression.
3.1.2. Linear orthotropic elasticity of wood
It is assumed that wood is a continuous, elastic, homogeneous orthotropic medium
admitting a cylindrical symmetry hardware [11, 12]. Then, we adopt the system of
orthogonal axes (R, T, L) for this study (figure 2).
(a) (b)
Figure 2: (a) System of cylindrical symmetry coordinates, (b): Test tube oriented along the
symmetry axes [12].
In the base (1, 2, 3), the elastic behaviour of the material is characterized by the
tensor of the compliances (Sij) which links the strain tensor (ij) to the stress (ij)
tensor:
TR
LR
LT
L (3)
T (2)
R (1)
R
L
T
TR
LR
LT
L (3)
T (2)
R (1)
TR
LR
LT
L (3)
T (2)
R (1)
R
L
TR
L
T
4. Anisotropic Behaviour of Natural wood Palmyra (Borassus Aethiopum Mart) of Chad
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12
31
23
3
2
1
66
55
44
333231
232221
131211
12
31
23
3
2
1
S00000
0S0000
00S000
000SSS
000SSS
000SSS
2
2
2
(1)
In the basic (R, T, L), equation (1) becomes:
RT
LR
TL
L
T
R
RT
LR
TL
LT
TL
R
RL
L
LT
TR
RT
L
LR
T
TR
R
RT
LR
TL
L
T
R
G
1
00000
0
G
1
0000
00
G
1
000
000
E
1
EE
000
EE
1
E
000
EEE
1
(2)
Modulus EL, ER and ET in the directions L, R and T, respectively, are defined by:
11
R
S
1
E ,
22
T
S
1
E ,
33
L
S
1
E (3)
The coefficients of Poisson RT RL, TR, LT, LR, and TL are given by the following
relationships:
11
31
RL
33
23
LT
22
12
TR
33
13
LR
22
32
TL
11
21
RT
S
S
,
S
S
,
S
S
S
S
,
S
S
,
S
S
(4)
The shear modulus GLR, GLT and GRT in the planes LR, LT and RT, respectively, are
defined for a rosette orthogonal by:
TLTLTLTLT
2
L
2
LTTL
66
RT
RLRLRLRLR
2
L
2
LRRL
55
LR
RTTRTRTRR
2
T
2
TRTR
44
LT
EEE2EE4E
EEE
S
1
G
EEE2EE4E
EEE
S
1
G
EEE2EE4E
EEE
S
1
G
(5)
The components Cijkl of elastic stiffness tensor allow calculating the components kl
of stress tensor according the components ij of strain:
klijklij C (6)
5. Ngargueudedjim K, Annouar D. M, G.E. Ntamack, S. Charif D’ouazzane And Bianpambe H. W
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3.2. Testing equipment
3.2.1. The strain gauge rosettes used
The rosette used comprises 3 gauges type CEA-06-240UZ-120 arranged at 45°. Its
dimensions are 16x10 mm. The active length of the gate of the gauge is 5mm (upper
3mm minimum recommended value in literature) it is sufficient to integrate the
macroscopic effect of the deformations of the material. The gauge dimensions are also
sufficient to allow for the dissipation of heat, therefore, to ensure greater compatibility
with a correct answer of the dynamic phenomena and gradients stress. Their
resistance and factor are R=120 and K=2.055, respectively.
3.2.2. Device tests
The test device (Figure 3) comprises
- 2 bridges strain type P3 of VSHAY Micromesures Firm. They have 4
independent channels and a dial LCD display. This bridge provides a facility for
setting the resistance, the gauge factor, the type of mounting of the bridge and the unit
of measurement.
- 1 bending and twisting machine designed and manufactured in the Exact and
Applied Sciences Faculty of University of N’Djamena-Chad. It is equipped with a
hydraulic system ENERPAC brand louse weight bearing. The maximum pressure of
the pump of the hydraulic system is 70bars. The piston of the hydraulic system is set
down in a vertical position for the occasion. Its diameter and maximum stroke are
25.3mm and 25mm respectively.
Figure 3 Device testing and specimens in position of test compression
3.3. Preparation of test specimens and conducting trials
The six specimens for the adopted method of characterization are collected from the
base of palmyra at 1m from the ground, especially in the part of the heartwood after
wood splitting into 4 parts (Figure 4) as follows:
- 3 specimens in main directions R, T and L,
- 3 specimens in tangential directions at 45° in the plans RT, RL and TL.
After their machining milling to dimensions 25x25x40mm, the two adjacent side
surfaces to receive the rosettes were polished to P800 sandpaper. The alignment pins
of the gauges on the surfaces have been drawn in pencil hard lead. These surfaces
have been degreased, cleaned and dried in the open air under the sun. The gauges are
cleaned resin solvent and neutralized before being glued with the M200 cyanoacrylate
Piston
Specimen
Bridge
strain P3
Hydraulic
pump
6. Anisotropic Behaviour of Natural wood Palmyra (Borassus Aethiopum Mart) of Chad
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superglue. Next, the connecting wires are welded on each gauge in quarter (1/4) of the
Wheatstone bridge mounting (figure 5).
Figure 4: Specimens for the six pieces method.
Figure 5 Test specimen with 2 diagonal rosettes (3 gauges at 45°).
To prevent the erosion of borders and ensure the proper distribution and alignment
of the load, a square steel plate side 30mm and 5mm thick is placed on each of the
two charging tips of the specimen. Each specimen is tested at 351.90 N (7 bars) of
magnitude compressive force tree times. The average values of deformations recorded
manually permits the calculation of the components of the tensor of the strain’s
coefficients.
4. RESULT AND DISCUSSIONS
The values of the observed deformations were used to calculate the tensor
components of the elastic compliances (table 1).
Rosettes
Connecting
wires
7. Ngargueudedjim K, Annouar D. M, G.E. Ntamack, S. Charif D’ouazzane And Bianpambe H. W
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Table 1 Elastic compliances of Palmyra
S11 S22 S33 S12 S21 S13
-5,21.10-4 -6,15.10-4 - 2,0.10-4 8,28.10-4 -2,89.10-4 8,69.10-5
S31 S23 S32 S44 S55 S66
5,42.10-5 -3,34.10-5 -6,05.10-5 1,20.10-3 5,97.10-3 1,29.10-3
The Young's modulus (table 2), the Poisson's ratios (table 3) and the Coulomb’s
modulus (table 4) are calculated by using the values of the compliance.
Table 2 Young’s modulus of Palmyra
EL (MPa) ER (MPa) ET (MPa)
5005.68 1918.17 1630
Table 3 Poisson’s coefficient of Palmyra
RT LT LR TR RL TL
0,55 0,43 0,16 0,13 0,10 0,09
Tableau 4 Coulomb’s modulus of Palmyra
GLR (MPa) GTL (MPa) GRT (MPa)
834.51 775.88 167
It is observed from Table 2 that the longitudinal Young's modulus EL has a higher
value than the radial and tangential modulus. Indeed, fibers are reinforcing elements
along the major axis; they are coated by a softer matrix consisting of the common
lamella. Thus, since the majority of fibers will be oriented along the axis of the trunk,
this will give a fibrous reinforcement in the longitudinal direction and consequently a
higher Young's modulus. Woody rays constitute reinforcement along the radial axis
and that is why the ER value is greater than that of ET. The cells constituting the
woody radius induce a strengthening in the radial direction relative to the tangential
direction. Under a tangential force, the longitudinal fibers and woody radius are
charged perpendicularly to the long axes of the cells, which give a low tangential
modulus [10]. The shear modulus GLT in the longitudinal plane-tangential is very high
because this plane contains the longitudinal fibers and woody radius which improves
on the shear strength. In the radial-tangential plane, the crystalline polymers
(cellulose) and amorphous polymers (lignin and hemicellulose) are cut, which makes
easier shearing.
Table 4 Young's modulus of Palmyras heartwoods on 2 different areas in Chad
Origin of Chadian
Palmyra
Longitudinal elastic modulus (Young’s modulus)
(MPa)
EL ER ET
Malfana 5005.68 1918.17 1630
Houndouman [12] 6400 199.83
Table 4 shows the effect of the maturity of the tree on the mechanical properties
of the wood. Indeed, the Palmyra of Houndouman (at 15°04.47 east longitude and
11°51.33 North latitude) is oldest (40 years) than that of Malfana (30 years) standed at
8. Anisotropic Behaviour of Natural wood Palmyra (Borassus Aethiopum Mart) of Chad
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15°15.113 east longitude and 11°11.771 north latitude. Its heartwood is more resistant
(EL = 6400 MPa) than Malfana’s one (EL = 5005.68 MPa).
Tables 2, 3 and 5 highlight anisotropic nature of palmyra wood. Indeed, the
anisotropy of the wood results in the following order relationships:
- EL >> ER > ET for Young's modulus [12],
- GLR > GTL > GRT for shear modulus and RT > LT >> LR > TR > RL > TL for
the Poisson's ratios [10].
Table 5 Poisson's coefficients at 12% moisture content of the wood Palmyra with other
species [10].
Essence (kg/m3
) RT LT LR TR RL TL
Douglas 650 0.52 0.47 0.17 0.21 0.05 0.02
Spruce 450 0.42 0.40 0.34 0.38
Pine 490 0.45 0.44 0.39 0.39
Oak 560 0.6 0.57 0.39 0.18 0.04 0.02
Palmyra 823.22 0.55 0.43 0.16 0.13 0.10 0.09
Compared to other woods (table 5), the Palmyra wood has a low coefficient of
shrinkage in LR TR and LR plans. This can be explained by its consistency due to its
high lignin content (23.66%). His withdrawal coefficients in the RT plans, LT and LR
are close to the timber Douglas. Table 6 shows that the wood Palmyra is stronger than
spruce and Douglas in the shear plan RS and RT. Their shear modulus is similar to
those of pine and oak in the LR and LT plans. Its radial and tangential Young's
modulus are much higher than those of spruce, pine, Douglas and oak. Paradoxically,
the longitudinal Young's modulus of Palmyra is 10 times lower than those of other
timber. Palmyra Heartwood of Houndouman tested has given the longitudinal
Young's modulus of 6400 MPa in compression and 15044 MPa in flexure [13]. In
reality, flexural strength of high quality wood often exceeds the compressive strength
[12]. But this enormous gap values requires careful thought because the only
anisotropic character is not enough. Its anatomical structure which is heavily
composed of coarse fibers (figure 5) seems one explanation of this comportment. Like
other wood, Palmyra has Young’s modulus and Coulomb’s modulus well below those
of monvingui.
Table 6 Coulomb's modulus of Palmyra with other species to 12% of wood humidity
Essence Palmyra Douglas [10]
Spruce
[14]
Pine [10] Oak [10] Monvingui [14]
(kg/m3
) 823.22 470 390 490 560 760
EL (MPa) 5005.68 16872 11800 16015 15248 16000
ER (MPa) 1918.17 949 920 1182 1182 2490
ET (MPa) 1630 934 510 616 616 1730
GLR (MPa) 834.51 749 760 828 828 1410
GLT (MPa) 775.88 802 730 688 688 1230
GRT (MPa) 167 114 40 320 320 550
9. Ngargueudedjim K, Annouar D. M, G.E. Ntamack, S. Charif D’ouazzane And Bianpambe H. W
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Table 7 Poisson's coefficients of Palmyra with Broad-leaved tree and resinous to 12% of
wood humidity
Essence (kg/m3
) RT LT LR TR RL TL
Broad-leaved
tree [10]
650 0.67 0.46 0.39 0.38 0.048 0.033
Resinous [10] 450 0.51 0.43 0.39 0.31 0.03 0.02
Palmyra 823.22 0.55 0.43 0.16 0.13 0.10 0.09
Table 8: Coulomb's coefficients of Palmyra with Broad-leaved tree and resinous to 12% of
wood humidity.
(kg/m3)
GTL
(MPa)
GLR
(MPa)
GTR
(MPa)
EL/ER GLR/GTR GTL/GTR
Broad-leaved
tree [10]
650 971 1260 366 12,1 à 62 3,4 2,6
Resinous [10] 450 745 862 83,6 40,6 à 182 10,3 8,9
Palmyra 823.22 775.85 834.51 167 5,0 4,6
Tables 7 and 8 show that Palmyra is a special wood whose mechanical
characteristics are similar to those of resinous.
5. CONCLUSION
The objective of this work is was to characterize the mechanical wood Palmyra of
Chad. The study has identified its elastic compliances, its elastic constants (Young's
modulus, Coulomb’s modulus and Poisson's ratios) using the method of six
specimens. The test results of this study corresponds to what is reported in the
literature. In the same test conditions, the Young's modulus in the longitudinal
direction is much higher than the radial and tangential modulus. The values of
different elastic constants found confirm the anisotropic nature of Palmyra wood. The
comparison on the elastic constants of 2 individuals of different ages (30 and 45
years) showed that the Young's modulus of the Palmyra heartwood depends strongly
of the maturity of the tree. Compared to other species, wood Palmyra seems very
durable and has mechanical characteristics similar to those of oak wood. The results
of our tests give a longitudinal Young’s modulus well below those of other species;
this enormous gap values requires careful thought. The results of this work will
undoubtedly contribute to a better understanding of the mechanical behaviour of
Palmyra wood of Chad.
REFERENCES
[1] SAMBOU B, 1989. Rônier (Borassus aethiopum Mart.) et rôneraie au Sénégal
état actuel et conditions de restauration. Thèse de Doctorat, Université Cheick
Anta-Diop.
[2] GBAGUIDI A. L et al, 2011. Etude de la possibilité d’utilisation du rônier
comme armature végétal dans les éléments en béton cas de poutres. Anales des
Sciences Agronomique, 15(1).
[3] O.D. SAMAH et al, 2013. Caractérisations du rônier (Borassus aethiopum)
«COCKER», CASPIAN Journal: Management and High Technologies 3(23), pp
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[4] F. GBESSO, G. AKOUEHOU, B. TENTE et A. AKOEGNINOU, 2013. Aspects
technico-économiques de la transformation de borassus aethiopum Mart
(Arecaceae) au Centre-Bénin. Afrique Sciences 09(1), pp 159 – 173.
[5] AHMED A., DJIBRILLA A., CLERGÉ T, March 2010. Physico-chemical properties of
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[6] O. D. SAMAH et al, 2014. Determination of mechanical characteristics and
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[7] Ministère du Plan et de la Coopération, septembre 1976. Préparation d’un Projet
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[8] JACQUES R., juin 1993. Rapport de synthèse des activités du chantier
d’aménagement forestier de Ngam, 29 pages.
[9] BIANPAMBE H.W, 2014. Caractérisation structurale, physico-chimiques et
mécanique du bois rônier. Mémoire de master en Mécanique et Matériaux Faculté
des Sciences, Université de Ngaoundéré, 59P.
[10] GUITARD D, 1987. Mécanique du Matériau Bois et Composites. Editions
Cepadues, Toulouse, France.
[11] TSOUMIS G, 1991. Sciences and Technology of Wood: Structure, Properties,
Utilization. Van Nostrand Reinhold, New York, 9(3), Pp. 359-360.
[12] KOLLMANN F., W. Côté, 1968. Principles of wood Science and Technology.
Vol.1, Solid Wood. Springer-Verlag, New York.
[13] ALLARABEYE N, 2010, Caractérisation structurale, physico-chimiques et
mécanique du bois rônier. Mémoire de master en Electromécanique de l’Institut
Universitaire des Sciences et Techniques d’Abéché, 59P.
[14] BODIG J, GOODMAN R., 1973, Prediction of Elastic Parameters for Wood,
Wood Science, 5(4), 249-264.
[15] David Goodman and Arash Edalatnoor. Waste Just Another Resource: A Case
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[16] M. Sreekanth. Measurement of Devolatilization Time And Transient Shrinkage
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[17] Ramesh Chandra Mohapatra, Antaryami Mishra and Bibhuti Bhushan
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![Anisotropic Behaviour of Natural wood Palmyra (Borassus Aethiopum Mart) of Chad
http://www.iaeme.com/IJMET/index.asp 103 editor@iaeme.com
Key words: Borassus Aethiopum Mart, Wood, Anisotropic Material, Fiber,
Natural Composite.
Cite this Article: Ngargueudedjim K, Annouar D. M, G.E. Ntamack, S.
Charif D’ouazzane and Bianpambe H. W. Anisotropic Behaviour of Natural
wood Palmyra (Borassus Aethiopum Mart) of Chad, International Journal of
Mechanical Engineering and Technology, 6(9), 2015, pp. 102-111.
http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=6&IType=9
1. INTRODUCTION
The Palmyra is an angiosperm spermatophyte plant (class of monocotyledons) in the
class of palm. It grows in the African savannah [1]. He develops a trunk from 15m to
20m of length and 0.5m to 1.2m of diameter [2]. Its characteristics vary from one
region to another. Its wood has a woody tight structure, typical of palm trees, with
significant internal tensions [3, 4]. Unlike other woods whose heartwood (wood very
old and hard) is in the heart of the stem, Palmyras heartwood is located between
sapwood and bark. This wood rots hardly, even in water, and resistant to salinity. It is
not attacked by termites, marine borers and mushroom. It is an excellent lumber
which was widely used in civil engineering for the construction of bridges, wharves,
warehouses of infirmaries and in ports. Its fibrous structure and strength makes it a
material of choice carpentry and plastering. Finally, we note the recent use of this
wood in joinery and cabinet for manufacturing modern living rooms furniture, trunks
etc [1, 5, 6]. In Chad, we found plenty in the Sudano-Sahelian zone [7, 8]. In some
rapidly growing cities, It constitutes the frame of houses (walls supports, frames, door
and window frames, window frames). In rural areas, it is also widely used in
construction and as palisades support poles, in addition to many other domestic
purposes (manufacture beehives, seats, and shelters for domestic animals). Given its
importance in the construction work, knowledge of scientific data is essential to
define a strategy for the rational use. The work carried out concerning the extent of its
elastic constants as an orthotropic anisotropic material (natural composite).
Specifically, it is to determine its mechanical parameters which are the Young's
modulus, Poisson’s coefficients and shear modulus by using the 6 test method.
2. PLANT MATERIAL TESTING
The plant material is taken from a trunk of a male Palmyra tree aged of about 30
years. Its average height and bead diameter in the middle of the useful length (8m of
height) are respectively 16m and 34cm. The trunk is cut into pieces of 1.20m. The
piece of the base circumference of 1.46m is used for these experimental tests. The
sampling site is in the village Malfana at south of N'Djamena – Chad, located at
15°15.113 east longitude and 11°11.771 north latitude (figure 1).
Figure 1: Localization of Palmyra groves of the village Malfana.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)