MALAYSIAN TIMBER - Mechanical Properties

With over 58 per cent of its land area under natural forest, Malaysia is home to over 2,650 species, many of which are of commercial importance. Malaysia's location in the tropics means that its trees have 365 growing days in a year. This allows the trees ample time to grow and develop without seasonal interruptions.

Apart from its intrinsic beauty, wood is highly versatile, has good insulation properties and is strong yet easy to use. Malaysia has an endless selection of timbers from which to choose. Malaysian timbers have been utilised in various applications, including interior designs. The multitude of colours available represents an artist’s palette, enabling an endless expression of creativity.

This article focuses on statistical technique for the assessment of grouping tropical timbers into similar strength groups. The Student’s t-test was conducted to evaluate whether the values of mean MOE in bending of two timbers are statistically different from each other. A total of 23 Malaysian hardwoods of different strength classes were assessed by comparing MOE value of one timber to the next. The assessment is limited to species of data obtained from at least 40 specimens and from at least 5 trees. However, more species can be added by conducting extra test based on the similar test procedure. The results showed that from 23 timbers evaluated, they fall into 6 different levels, indicating 6 different timber groups of similar MOE. The outcome is almost similar to the previous groupings done through different methods. The grouping will serves as a guideline for converting small size specimens’ data into the equivalent structural timber test values.

Mechanical Properties

Name Botanical Name
Strength Group
Static Bending
Compression Strength
Shear Strength N/mm2
MOE N/mm2
MOR N/mm2
Perpendicular N/mm2
Parallel N/mm2
HEAVY HARDWOOD
Balau Shorea spp.
A
20,100
142
9.79
76
15
Bitis Madhuca utilis, palaquium ridleyi & P. Stellatum
A
23,800
171
12.48
90.3
15.4
Chengal Neobalanocarpus heimii
A
19,600
149
12
75.2
13.9
Giam Hopea spp.
A
16,500
122
11.17
58.9
15.9
Red Balau Shorea spp.
B
14.8K-17K
100-142
5.52
52.2 - 69.2
10 - 15
Merbau Intsia palembanica
B
15,400
116
9.17
58.2
12.5
Tembusu Fagraea spp.
B
14,000
100
8
52.1 - 60.6
10 - 14
Resak Vatica spp.
B
14.4K-18.1K
81-105
4.90 - 11.45
41.7 - 60.9
9.3 - 12.6
Keranji Dialium spp.
A
20,100
134
9.24 - 19.72
72
16
Kekatong Cynometra spp.
A
18,400
135
11.38
67
15.6
MEDIUM HARDWOOD
Kulim Scorodocarpus borneensis
A
14,900
107
5.10
57.0
10.3
Keruing Dipterocarpus spp.
B
17K-22.3K
91-133
4.34 - 9.17
50.2 - 68.1
9.2 - 12.3
Kempas Koompassia malaccensis
A
18,600
122
 7.52
65.6
12.4
Mengkulang Heritiera spp.
B
12K-16K
91-110
5.38
52.1 - 60.7
10.8 - 12.2
Merpauh Swintonia spp.
B
14K-18K
94-108
6.41 - 7.24
43.6 - 56.6
12.6 - 13.7
Meransi Carallia spp.
A
13.2K-13.4K
104-105
10.28 - 10.44
54.6 - 55.5
10.8 - 11
Mata Ulat Kokoona spp.
A
16,300
102
6.83
53.1
10.7
Rengas Gluta spp.
B
14,900
111
7.65
59.4
13.2
Punah Tetramerista glabra
A
15,400
87
5.72
49.4
9.7
Tualang Koompassia excelsa
A
17,800
121
8.0
62.0
16.3
Simpoh Dillenia spp.
B
14,300
76
5.03
39.4
8.2
Kasai Pometia spp.
C
17,000
106
5.31 - 9.52
49.3 - 53.5
13.4 - 14.3
Kelat Eugenia spp.
B
17,600
116
6.0
59.0
12.8
Keledang Artocarpus spp.
B
12.2K-15.5K
93-97
4.9
47.5 - 58.8
9.9 - 12.5
Kapur Dryobalanops spp.
B
13K-18.7K
114-126
5.52
61.7 - 69.6
9.9 - 12.5
Merawan Hopea spp.
B
15,000
90-92
5.10 - 5.59
46 - 51
9 - 9.3
LIGHT HARDWOOD
Melantai Shorea macroptera
C
7,900
46
2.21
24.5
6.3
Kungkur Pithecellobium spp.
B
10,700
89
6.62
44.1
12.8
KembangSemangkuk Scaphium spp.
C
15.3K-17K
92-93
n.a.
50.2-52
9.1-10.1
Medang Spp. of Lauraceae
C
10.1K-12.6K
64-93
3.19
34.2 - 52.1
7.5 - 7.7
Melunak Pentace spp.
C
2,000
85
4.28
43.6
10.8
Kedondong Spp. of Burseraceae
C
12.1K-12.9K
81
6.41
43.1 - 43.7
10.9 - 11.8
Jelutong Dyera spp. 
D
8,100
50
2.65
27.0
5.8
Machang Mangifera spp.
C
7.5K-14.8K
57-90
6.14
32.1 - 48.2
12.2 - 13.1
Ramin Gonystylus spp.
C
12K-16.4K
88-134
n.a.
48.8 - 72.4
8.5 - 11.9
Dark Red Meranti Shorea spp.
C
11.2K-13.9K
74-92
2.97 - 5.03
38.8 - 52.9
8 - 11.4
Mempisang Spp. of Annonaceae
C
13.4K-14.8K
80-85
3.65 - 4.62
41.4 - 51
8 - 11.5
Meranti Bakau Shorea uliginosa
C
14,700
68
3.38
25.9
6.7
Rubberwood Hevea brasiliensis
C
9,200
66
4.69
32.3
11
White Meranti Shorea spp.
C
11.5K-19.4K
90-132
3.86 - 11.08
44.3 - 67.1
9.4 - 14.2
Nyatoh Spp. of Sapotaceae
C
12.2K-18.3K
79-129
4.48 - 9.17
43.5 - 64.7
11 - 11.9
Mersawa Anisoptera spp.
C
9.2K – 19.2.6K
49-54
5.52 - 5.65
26 - 28.9
7.1 - 7.4
Light Red Meranti Shorea spp.
C
8.8K - 13.6K
63-83
2.41 - 2.51
34.5 - 48.2
6.3 - 11
Sepetir Sindora spp.
C
13,600
92
5.93
46.3
13.6
Gerutu Parashorea spp.
C
13,600
118
8.44
59.8
11.2
Pulai Alstonia spp.
D
7,100
43
n.a.
24.8
6.3
Yellow Meranti Shorea spp.
C
10K - 12.4K
67-88
2.97
40 - 50.6
8 - 10.5
Petai Parkia spp.
D
10,700
55.0
n.a.
30.8
7.4
Geronggang Cratoxylum spp.
D
8,000
40
1.93
18.3
5.1
Durian Durio spp., Neesia spp.
C
9.5K - 15.8K
65-95
2.72 - 5.65
32.5 - 53.9
6.8 - 9.2
Bintangor Calophyllum spp.
C
14,300
74
3.19
36.7
10.8
Sesendok Endospermum spp.
D
8,500
39
1.75
20.8
5.4
Terap Artocarpus spp.
D
10.3K - 12.1K
67-68
3.03 - 3.17
34.8 - 35
9.2
Penarahan Spp. of Myristicaceae
C
9,380
51
5.65
43.6
9.6
Perupok Lophopetalum spp.
C
12.2K - 12.6K
76-79
5.21 - 5.50
42.5 - 43.5
7.4 - 9.0
Terentang Campnosperma spp.
D
7,000
42
2.21
22.4
7.5
SOFTWOOD (Conifers)
Damar Minyak Agathis borneensis
D
12,000
66
n.a.
33.6
6.9
Podo Podocarpus spp.
C
10,500
n.a.
n.a.
48.5
7.8

Bending tests

Bend tests provide a quick and simple way to determine the strength and deformation properties of wood and timber products. The test is also particularly relevent in this application because wood is frequently used in the form of beams where resistance to bending is an important parameter.
A range of fixtures is available to cater for various specimen sizes and strengths. All fixtures can be equipped with a range of optional support rollers some of which feature articulation to cater for warped specimens. The range of fixtures is ideal for tests on MDF and fiberboard as well as natural timber.

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Comment:-

Michanical Properties

The mechanical properties have been determined using the test procudure described in ASTM designation: D143-52 developed by the American Socity for Testing Materials.

Strength group

Four strenth groups are used, viz., strength groups A,B,C and D. The earlier grouping method(Burgess,1958) based solely on compession strength parallel to grain is given in the table below.

STRENGTH GROUPING TABLE
Strength Group
Compression Stength parallel to grain(N/mm2)
A
greater than 55.2; Extremely strong
B
41.4 - 55.2; Very strong
C
27.6 - 41.4; Moderately strong
D
Less than 27.6; weakest

A refinement to the earliar method took into consideration the basic and grade stresses(Engku Abdul Rahman, 1960). Spme timbers have been grouped using this method. For the remaining timbers, the earlier grouping has been used.

Static bending

Data on the Modulus of Elasticity(MOR) and Modulus test data (Lee et al,1979) the mean values are given in the air -dried condition(unless otherwise indicated). If a range is given, it shows the lowest and highest for the timber group.

Compression strenth

Data on compression strenth perpendicular to gain and compression strength parallel to grain have been obtained from published test data(Lee et al, 1979). If a range is given, it shows the lowest and highest values found for each timber.

Shear strenth

Data on shear strength have been obtained from published test data(Lee et al, 1979). If a range is given, it shows the lowest and highest values found for each timber.

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