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NONDESTRUCTIVE AND DESTRUCTIVE EVALUATION OF WOOD STRENGTH AND ITS RELATION TO CELLULAR MICROSTRUCTURE
Nurul Faziha binti Ibrahim
Master of Science 2010
J "' 1 laJUUmal Axuuc OJ ilVERSITI MALAYSIA SARA\V,
P.KHIDMAT MAKLUMAT AKADEMIK
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NONDESTRUCTIVE AND DESTRUCTIVE EVALUATION OF WOOD STRENGTH AND IT'S RELATION TO CELLULAR MICROSTRUCTURE
NURUL F AZIHA BINTI IBRAHIM
A thesis submitted In fulfillment of requirements for the degree of Master Science
Faculty of Resource Science and Technology UNIVERSITI MALAYSIA SARAW AK
2010
DECLARATION
No portion of the work referred to in this dissertation has been submitted in support of an application for another degree of qualification of this or any other university or institution of higher learning.
;=ei i
Nurul Faziha Binti Ibrahim
Faculty of Resource Science and Technology
Universiti Malaysia Sarawak
ACKNOWLEGMENT
First and foremost, I would like to thank the Faculty of Resource Science and
Technology, Faculty of Engineering and the Centre of Graduate Studies, UNIMAS for
providing me the opportunity, scholarship and facilities to conduct this research.
I also would like to extend my gratitude and appreciation to my supervisor, Associate
Professor Dr. Ismail Jusoh and Associate Professor Dr. Sinin Hamdan for their invaluable
advice, constant support, guidance and patience throughout the process of this research.
I am also grateful to my fellow coursemates, Nur Afnie Farysha Binti Hamsah,
Sharifah Mona Abdul Aziz, Farawahida Abu Zahrin, Rezaur Rahman and Saiful Islam;
laboratory technicians, Mr. Salim, Mr. Rizan, Mr. Sabariman for their technical guidance,
kindness, friendship and company. I also would like to thank Timber Research and Technical
Training Centre (TRTTC) for their assistance in preparing my wood samples.
My sincere thanks and love go to my parents, Ibrahim Bin Jusoh and Naemah Binti
Mat Zin; brother, Mohd Fahizan, sisters, Filzana, Ida Firdaus, Fadzilah and Fatin Nadia for
their encouragement and moral support.
11
ABSTRACT
(Non-destructive evaluation (NDE) of wood is a method of identifying wood quality without
damaging the samples and its eliminate the tedious specimen preparation in order to determine
the mechanical properties of wood. Wood properties can be determined rapidly by in situ
inspection during its service life or measured directly from standing trees without reducing the
economic value of its timber. This study assess the feasibility of free-free flexural vibration
method, one of NDE techniques for estimating the wood stiffness of plantation species
namely Acacia mangium, Hevea brasiliensis and Paraserianthes mOluccanaJ The specific
objective of this study were (i) determine the dynamic modulus of elasticity (DMOE) on the
three plantation species, (ii) establish the relationship between DMOE obtained from non
destructive and modulus of elasticity (MOE), modulus of rupture (MOR), Young's modulus
(E) and maximum crushing strength (MCS) obtained from destructive test, (iii) evaluate the
effects of tension wood on DMOE, MOE and MaR, and (iv) analyze the relationship between
anatomical properties and mechanical properties. For this purpose, wood specimens with
dimension 20 mm (T) x 10 mm (R) x 340 mm (L) were prepared for non-destructive test
according to tension wood and opposite wood to determine DMOE. The results from the non
destructive test were compared with destructive tests namely three-point bending and
compression parallel to grain where the samples were .prepared according to the British
Standard. The DMOE was also compared with MOE and MOR obtained from three-point
bending test using the non-destructive test's samples. Results showed that tension wood
recorded greater DMOE mean values than opposite wood. A. mangium recorded higher
DMOE in both tension and opposite wood followed by H brasiliensis and P. moluccana.
Destructive tests also showed that A. mangium recorded the highest mean MOE and MaR
III
values followed by H brasiliensis and P. moluccana as determined by three-point bending
test. Regression analyses showed that strong relationship were observed between DMOE and
MOE detennined from non-destructive samples (ND samples) in both of tension (r= 0.92)
and opposite wood (r2=0.79). However, DMOE and MOE obtained from British Standard
samples (BS samples) were not correlated. In order for DMOE to be meaningful and able to
predict MOE, correction factor has to be introduced to DMOE. Following inclusion of
correction factor (CF), DMOE' was significantly correlated with MOE in A. mangium
(R=0.80 and 0.88) and H brasiliensis (R=0.85 and 0.90) in tension and opposite wood,
respectively. However, it did not successfully determined DMOE' in P. moluccana due to its
low density that yielded large CF values. Between DMOE and MOR, only tension wood
recorded good relationship (r2=0.70) compared to opposite wood (r2=0.46) in all species
combined from ND samples. Anatomically, tension wood is characterized by thicker fibre
wall, longer fibre, larger fibre diameter, smaller vessel diameter and small microfibril angle
(MFA). The relationship between anatomical properties and mechanical properties showed
that fibre wall thickness gave significant effect on DMOE in all individual species in both of
tension and opposite wood. The fibre wall thickness significantly effect the MOE and MOR in
all individual species in tension wood but only A. mangium and P. moluccana in opposite
wood. For all species combined, fibre length was significantly correlated with DMOE, MOE
and MOR in tension wood but only correlated to MOR in opp<?site wood. Ray height was
significantly correlated with DMOE and MOE in opposite wood of the species studied. Fibre
lumen diameter and fibre diameter were significantly correlated with MOE and MOR only in
opposite wood. From the results, it can be concluded that the free-free flexural vibration
method has the potential to predict the mechanical properties of the plantation species.
IV
UJIAN TANPA MUSNAH DAN MUSNAH KEKUATAN KAYU DAN
HUBUNGANNYA DENGAN STRUKTUR MIKRO SEL
ABSTRAK
Ujian tanpa musnah (NDE) ialah satu kaedah untuk mengenal pasti kualiti kayu tanpa
merosakkan sampel dan menghapuskan penyediaan sampel yang remeh. Sifat-sifat kayu dapat
ditentukan berulang kali dengan menguji secara 'in situ' semasa servis atau secara terus dari
pokok tanpa menyusut nilai ekonomi kayu tersebut. Kajian ini melihat keupayaall kaedah
getaran melintang secara bebas untuk mengukur kekuatan spesies ladang hutan iaitu Acacia
mangium. Hevea brasiliensis dan Paraserianthes moluccana. Objektif spesijik kajian ini
adalah untuk (i) menentukan modulus kekenyalan dinamik (DMOE) ke atas tiga spesies
ladang hutan, (ii) menentukan hubungan antara DMOE diperolehi daripada ujian tanpa
musnah dan modulus kekenyalan (MOE), modulus patahan (MOR), modulus Young (E) dan
kekuatan musnah maksimum (MCS) diperolehi daripada ujian musnah, (iii) menguji kesan
kayu tegangan terhadap DMOE, MOE, MOR, E dan MCS dan (iv) menguji hubungan di
antara sifat-sifat anatomi dan sifat-sifat mekanikal. Bagi tujuan ini, spesimen kayu bersaiz 20
mm (T) x 10 mm (R) x 340 mm (L) telah disediakan untuk ujian tanpa musnah mengikut kayu
tegangan dan kayu normal untuk menentukan DMOE. Keputusan dari ujian tanpa musnah
ujian musnah iaitu lenturan tiga litik dan mampatan selari iradibandingkan dengan
mengguna piawai British. DMOE juga dibandingkan dengan MOE dan MOR diperolehi dan
lenturan tiga titik menggunakan sampel ujian tanpa musnah. Keputusan ini menunjukkan
kayu tegangan mencatatkan nilai DMOE yang tinggi berbanding dengan kayu norma/. A.
mangium mencatatkan DMOE yang tinggi dalam kayu tegangan dan kayu normal diikuti oleh
v
H brasiliensis dan P. moluccana. Ujian musnah juga menunjukkan A. mangium mencatatkan
purata nilai MOE dan MOR tertinggi diikuti oleh H brasiliensis dan P. moluccana yang
ditentulcan dari ujian lenturan tiga titik. Keputusan analisis menunjukkan hubungan yang kuat
antara DMOE dan MOE yang ditentukan dari sampel tanpa musnah (sampel ND) dalam kayu
tegangan (r2= 0.92) dan kayu normal (r2=0. 79). Walau bagaimanapun, tiada korelasi antara
DMOE dan MOE diperolehi dari sampel mengikut piawaian British (sampel BS). Untuk
menjadilcan DMOE lebih bermakna dan dapat meramalkan MOE, laktor pembetulan telah
diperkenallcan terhadap DMOE. Sebaik sahaja kemasukan laktor pembetulan (CF), DMOE'
didapati berkorelasi secara signifikan terhadap MOE dalam A. mangium (R=0.80 dan 0.88)
dan H brasiliensis (R=0.85 dan 0.90) masing-masing dalam kayu tegangan dan kayu normal.
Walau bagaimanapun, DMOE' tidak sesuai diaplikasikan dalam P. moluccana kerana
ketumpatannya yang am at rendah menyebabkan julat CF yang terlalu besar. Antara DMOE
dan MOR, hanya kayu tegangan mencatatkan hubungan yang baik (/=0.70) berbanding kayu
normal (/=0.46) dalam kombinasi semua spesies dari sampel ND. Berdasarkan anatomi,
kayu tegangan bercirikan dinding gentian yang tebal, gentian yang panjang, diameter gentian
yang besar, diameter liang yang kecil, dan sudut mikrojibril (MFA) yang kecil. Hubungan
antara sifat anatomi dan mekanikal menunjukkan ketebalan dinding gentian menunjukkan
kesan yang signifikan terhadap DMOE dalam semua spesies sama ada dalam kayu tegangan
dan kayu normal. Ketebalan dinding gentian juga memberi kesan signifikan terhadap MOE
dan MOR dalam semua spesies individu dalam kayu tegangan tetapi hanya A. mangium dan
P. moluccana dalam kayu normal. Kombinasi data bagi semua spesies menunjukkan panjang
gentian berkorelasi secara signifikan terhadap DMOE, MOE dan MOR dalam kayu tegangan
lelapi hanya berkorelasi terhadap MOR dalam kayu normal. Panjang ruji berkorelasi secara
signifilcan terhadap DMOE dan MOE dalam kayu normal. Diameter lumen gentian dan
VI
diameter gentian berkorelasi terhadap MOE dan MaR. Kesimpulan dari kajian ini
menunjukkan bahawa kaedah getaran melintang bebas berpotensi meramalkan sifat
mekanikal spesies ladang hutan.
VB
Pu at Khidm~ lJu..nlllt Akad mi... UNIVERSITI MALA S SAI{AW K
TABLE OF CONTENTS
Page
DECLARATION
ACKNOWLEDGMENT 11
ABSTRACT
TABLE OF CONTENTS Vlll
III
ABSTRAK v
xiiLIST OF FIGURE
LIST OF TABLE xv
LIST OF SYMBOLS XIX
LIST OF APPENDICES xx
CHAPTER ONE: INTRODUCTION
1.1 Background 1
41.2 Objectives
CHAPTER TWO: LITERATURE REVIEW
2.1 Acacia mangium Willd. 7
2.2 Hevea brasiliensis Muell. Arg. 11
2.3 Paraserianthes moluccana (L.) Nielsen 14
2.4 Properties of tension wood 17
2.5 Non-destructive evaluation techniques 20
2.6 Principle of free-free flexural vibration 30
2.7 Dynamic Modulus of Elasticity (DMOE) 30
Vlll
332.8 Relationship between anatomy and wood properties
CHAPTER THREE: MATERIALS AND METHODS
373.1 Sample collection
403.2 Non-destructive testing
3.2.1 Experimental apparatus 40
3.2.2 Determination of DMOE using free-free flexural vibration 45
3.3 Destructive testing 46
3.3.1 Static bending test 46
3.3.2 Compression parallel to grain 48
3.4 Quantification of anatomical properties 50
3.4.1 Wood material 50
3.4.2 Cube softening 50
3.4.3 Cube sectioning 51
3.4.4 Staining 51
3.4.5 Permanent mounting 51
3.4.6 Determination of fibre length 52
3.4.7 Determination of microfibril angle (MFA) 53
3.4.8 Measurement of anatomical parameter 54
3.5 Determination of air-dry density and specific gravity 57
573.6 Data analyses
CHAPTER FOUR: RESULTS
594.1 Vibrational properties of plantation species
IX
Dynamic Modulus of Elasticity (DMOE) 60
Modulus of Elasticity (MOE), Modulus of Rupture (MOR), 61
Young's Modulus (E) and Maximum Crushing Strength (MCS)
Anatomical properties of Acacia mangium, Hevea brasiliensis 64
and Paraseriathes moluccana
4.5 Air-dry density and specific gravity ofAcacia mangium, Hevea brasiliensis 67
and Paraseriathes moluccana
4.6 Relationship between MOE and MOR, and E and MCS 69
4.7 Variation of MOE and MOR values determined from 77
ND samples and BS samples
4.8 Relationship between DMOE and frequency 79
4.9 Relationship between DMOE and MOE and MOR 81
modulus of elasticity (MOE), and modulus of rupture (MOR)
4.10 Relationship between DMOE' and MOE following application of 88
correction factor
4.l1 Effect of anatomical properties on DMOE, MOE and MOR 92
4.11.1 Effect of anatomical properties on DMOE 92
4.11.2 Effect of anatomical properties on MOE 97
4.1l.3 Effect of anatomical properties on MOR 100
4.l2 Relationship DMOE and air-dry density 104
CHAPTER FIVE: DISCUSSION
5.l Dynamic Modulus of Elasticity (DMOE), Modulus of Elasticity (MOE), 107
Modulus of Rupture (MOR), Young's Modulus (E) and
x
Maximum Crushing Strength (MCS) of plantation species
5.2 Relationship among DMOE and MOE, and MOR 110
5.3 The effect of tension wood on non-destructive and destructive properties 113
of plantation species
1165.4 The effect of anatomical properties on DMOE, MOE and MOR
CHAPTER SIX: SUMMARY AND CONCLUSION
6.1 Summary 120
1226.2 Conclusion
125REFERENCES
xi
Figure
LIST OF FIGURE
Descriptions Page
Figure 3.1 Sampling for bolt 1, bolt 2 and bolt 3 38
Figure 3.2 (a) Sampling for tension and opposite wood for each bolt 39
(b) The cross section of tension and opposite wood
Figure 3.3 Sample preparation scheme from the log 39
Figure 3.4 Schematic diagram offree~free flexural vibration method 40
Figure 3.5 Free-free flexural vibration testing system 41
Figure 3.6 An example of natural frequency of wood specimen obtained from 43
free-free flexural testing system using Ix resolution
Figure 3.7 An example of natural frequency of wood specimen obtained from 43
free-free flexural testing system using 20x resolution
Figure 3.8 The ratio of nodal point from free ends to length of sample (xiI) 44
for mode 1
Figure 3.9 Three-point bending test 47
Figure 3.10 Scheme for determination of specific gravity, anatomical properties 48
and fibre length from bending specimen failure
Figure 3.11 Compression parallel to grain 49
Figure 3.12 Position of sections 52
Figure 3.13 Photomicrograph of fibre under confocal laser scanning microscope 53
Figure 3.14 Photomicrograph of microfibril angle (MFA) under compound 54
Microscope, 40x
Figure 3.15 Photomicrograph of (a) fibre cell with G-Iayer in H brasiliensis, 56
xii
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Figure 4.6
Figure 4.7
(b) fibre cell in P. moluccana, (c) vessel in H brasiliensis and
(d) ray cells in A. mangium
Relationship between MOE and MOR in ND samples 70
(20 mm (T) x 10 mm (R) x 340 mm (L)) for A. mangium,
H brasiliensis and P. moluccana in (a) tension wood and
(b) opposite wood
The relationship between MOE and MOR in BS samples 71
(20 mm (T) x 20 mm (R) x 300 mm (L)) for A. mangium,
H brasiliensis and P. moluccana in (a) tension wood and
(b) opposite wood
The relationship between MOE and MOR in ND samples 72
(20 mm (T) x 10 mm (R) x 340 mm (L)) for all species combined m
(a) tension wood and (b) opposite wood
The relationship between MOE and MOR in BS samples 73
(20 mm (T) x 20 mm (R) x 300 mm (L)) for all species combined in
(a) tension wood and (b) opposite wood
The relationship between E and MCS in A. mangium, 75
H brasiliensis and P.moluccana in (a) tension wood and
(b) opposite wood
The relationship between E and MCS for all species combined in 76
(a) tension wood and (b) opposite wood
The relationship between DMOE and frequency in A. mangium, 80
H brasiliensis and P. moluccana in (a) tension wood and
(b) opposite wood
Xlll
Figure 4.8 The relationship between DMOE and MOE in A. mangium, 82
H brasiliensis and P. moluccana for ND samples
(20 mm (T) x 10 mm (R) x 340 mm (L)) in (a) tension wood and
(b) opposite wood
Figure 4.9 The relationship between DMOE and MOE for all species combined 83
in ND samples (20 mm (T) x 10 mm (R) x 340 mm (L)) in
(a) tension wood and (b) opposite wood
Figure 4.10 The relationship between DMOE and MOR in A. mangium, 86
H brasiliensis and P. moluccana for ND samples
(20 mm (T) x 10 mm (R) x 340 mm (L)) in (a) tension wood and
(b) opposite wood
Figure 4.11 The relationship between DMOE and MOR for all species combined in 87
ND samples (20 mm (T) x 10 mm (R) x 340 mm (L)) in (a) tension wood
and (b) opposite wood
Figure 4.12 The relationship between MOE and DMOE' in (a) tension wood and 91
(b) opposite wood from BS samples
Figure 4.13 The relationship between DMOE and density in A. mangium, 105
H. brasiliensis and P. moluccana in (a) tension wood and
(b) opposite wood
Figure 4.14 The relationship between DMOE and density in all species combined 106
in (a) tension wood and (b) opposite wood
xiv
LIST OF TABLE
Table Descriptions Page
Table 2.1 Mean MOE, MOR, E and MCS values ofA. mangium 9
Table 2.2 Average values of fibre length, fibre diameter, fibre lumen diameter, 10
fibre wall thickness, vessel diameter, ray height and ray diameter of
A. mangium
Table 2.3 Mean MOE, MOR, E and MCS values of H brasiliensis 12
Table 2.4 Average values of fibre length, fibre diameter, 14
fibre wall thickness, vessel diameter, ray height, vessel frequency
and ray frequency of H brasiliensis
Table 2.5 Mean MOE and MOR values of P. moluccana 16
Table 2.6 Average values of fibre length, vessel diameter and vessel 16
frequency of P. moluccana
Table 2.7 The wood study using differences of non-destructive techniques 26
Table 3.1 Tree characteristics of A. mangium, H brasiliensis and P. moluccana 38
Table 4.1 Mean values of natural frequency in tension and opposite wood of 60
A. mangium, H brasiliensis and P. moluccana
Table 4.2 Mean values of DMOE in tension and opposite wood of 61
A. mangium, H brasiliensis and P. moluccana
Table 4.3 Mean values of MOE and MOR in tension and opposite wood obtained 62
according to British Standard (B.S.373: 1957)
Table 4.4 Mean values of MOE and MOR in tension and opposite wood obtained 63
xv
For ND samples determined destructively using British Standard
Table 4.5 Mean values of E and MCS in tension and opposite wood of 64
A. mangium, H brasiliensis and P. moluccana
Table 4.6 Comparison of anatomical properties in tension wood and 65
opposite wood of A. mangium
Table 4.7 Comparison of anatomical properties in tension wood and 65
opposite wood of H brasiliensis
Table 4.8 Comparison of anatomical properties in tension wood and 66
opposite wood of P. moluccana
Table 4.9 Mean air-dry density and specific gravity in A. mangium, 68
H brasiliensis and P. moluccana of tension and opposite wood
Table 4.10 Comparison between mean air-dry density determined in 68
tension wood and opposite wood of A. mangium, H brasiliensis
and P. moluccana
Table 4.11 Differences between ND samples and BS samples in terms of MOE 78
and MOR in A. mangium, H brasiliensis and P. moluccana
in tension and opposite wood
Table 4.12 Differences between BS samples and ND samples in terms of MOE 78
and MOR for all species combined in tension and opposite wood
Table 4.13 Comparison between mean values ofDMOE and MOE in ND samples 84
Table 4.14 Pearson correlation (R) between DMOE and MOE, and DMOE and 88
MOR in tension and opposite wood in BS sample,
20mm (T) x 20mm (R) x 300mm (L)
xvi
Table 4.15 Pearson correlation between MOE and DMOE after the correction 90
factor was included in BS sample, 20mm (T) x 20mm (R) x 300mm (L)
Table 4.16 Multiple linear regression of anatomical properties on dynamic 93
modulus of elasticity (DMOE) in tension and opposite wood
of A. mangium
Table 4.17 Multiple linear regression of anatomical properties on dynamic 94
modulus of elasticity (DMOE) in tension and opposite wood
of H brasiliensis
Table 4.18 Multiple linear regression of anatomical properties on dynamic 95
modulus of elasticity (DMOE) in tension and opposite wood
of P. moluccana
Table 4.19 Multiple linear regression of anatomical properties on dynamic 96
modulus of elasticity (DMOE) for all species combined in tension
and opposite wood
Table 4.20 Multiple linear regression of anatomical properties on modulus of 97
elasticity (MOE) in tension and opposite wood of A. mangium
Table 4.21 Multiple linear regression of anatomical properties on modulus of 98
elasticity (MOE) in tension and opposite wood of H brasiliensis
Table 4.22 Multiple linear regression of anatomical properties on modulus of 99
elasticity (MOE) in tension and opposite wood of P.moluccana
Table 4.23 Multiple linear regression of anatomical properties on modulus of 100
elasticity (MOE) for all species combined in tension and opposite wood
Table 4.24 Multiple linear regression of anatomical properties on modulus of 101
rupture (MOR) in tension and opposite wood of A. mangium
XVll
4.25 Multiple linear regression of anatomical properties on modulus of 101
rupture (MOR) in tension and opposite wood of H brasiliensis
4.26 Multiple linear regression of anatomical properties on modulus of 102
rupture (MOR) in tension and opposite wood of P. moluccana
Multiple linear regression of anatomical properties on modulus of 103
rupture (MOR) for all species combined in tension and opposite wood
xviii
LIST OF SYMBOLS
= dynamic modulus of elasticity
= dynamic modulus of elasticity following inclusion of
correction factor
= modulus of elasticity
= modulus of rupture
= Young's modulus
= maximum crushing strength
=period of strain oscillation
= lateral deflection of beam
= distance along the beam
= speed of sound in the beam
= radius of gyration
= moment of inertia
= cross section of beam
= density of beam
= constant in Euller-Bernoulli elementary theory
= beam depth
= beam width
= beam length
= natural frequency of specimen
= mode of vibration
XlX
LIST OF APPENDICES
Figure AI: Photomicrograph of Acacia mangium tension wood sections, (a) transverse
section, 200x, (b) tangential section, 200x, (c) fibre cell, 600x and (d) radial
section, 200x using confocal laser scanning microscope
Figure A2: Photomicrograph of Acacia mangium opposite wood sections, (a) transverse
section, 200x, (b) tangential section, 200x, (c) fibre cell, 600x and (d) radial
section, 200x using confocal laser scanning microscope
Figure A3: Photomicrograph of Hevea brasiliensis tension wood sections, (a) transverse
section, 200x, (b) tangential section, 200x, (c) fibre cell, 600x and (d) radial
section, 200x using confocal laser scanning microscope
Figure A4: Photomicrograph of Hevea brasiliensis opposite wood sections, (a) transverse
section, 200x, (b) tangential section, 200x, (c) fibre cell, 600x and (d) radial
section, 200x using confocal laser scanning microscope
Figure A5: Photomicrograph of Paraserianthes moluccana tension wood sections, (a)
transverse section, 200x, (b) tangential section, 200x, (c) fibre cell, 600x and (d)
radial section, 200x using confocal laser scanning microscope
xx
figure A6: Photomicrograph of Paraserianthes moluccana opposite wood sections, (a)
transverse section, 200x, (b) tangential section, 200x, (c) fibre cell, 600x and (d)
radial section, 200x using confocal laser scanning microscope
XXI
CHAPTER ONE
INTRODUCTION
Background
In Malaysia, forest plantation began in 1957 with the planting of teak (Tectona
grandis) in northern state of Perlis and Kedah (Nik Muhamad and Paudyal, 1999). Then, the
plantation of tropical pine especially Pinus caribaea var. hondurensis took place which was
meant for pulp and paper industry. However, due to difficulty in obtaining good quality seeds
of P. caribaea, the plantation has been shifted to short-rotation (IS-years rotation) tropical
species such as Acacia mangium, Tectona grandis, Gmelina arborea and Falcataria
moluccana (Suharti et al., 1991). Recently, short rotation plantation areas has been steadily
increasing throughout the country for a raw material of wood fibre, solid wood products and
also pulp and paper industry (Nik Muhamad and Paudyal, 1999). Although fast-growing
plantation has been taking place, timber from natural forest is still the main source of timber
product. However, log production in the tropics had decreased in 1980s due to decreasing
forest area (Firmanti et al., 2005). To address the issue of log supply the government has been
promoting the utilization of planted timber for industrial utilization. One advantage of using
the plantation species is that the wood properties can be modified at a very basic level
according to physical and mechanical desired to meet the demand for wood based industry
(Zink-Sharp and Price, 2006).
Most physical and mechanical properties of wood can be measure by destructive
testing. However, the technique is sometimes wasteful and time consuming. Development of
fast, simple, non-destructive and accurate methods apparatus become important in forest
product industry. Non-destructive evaluation (NDE) is a science of identifying the physical
1