Final Report - Timber 2 (2)
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Timber Practical: Report Flexural Properties of Timber Members SANDRA LISTER N7457499 ENB273 – Civil Materials 5/6/2011
Investigation into relative performance of various timbers and timber products
SANDRA LISTER N7457499
Executive Summary This report presents the results and evaluations of the flexural properties of four types of timber products, namely softwood, hardwood, chipboard and plywood that are of interest to design engineers and architects. The aim of o f this experiment was to gain a more meaningful understanding of how various types of timber products vary in terms of stress, elastic limits, and resistance to bending. The approach taken was the standard three-point flexure test. Included are particulars on visual strength grading, testing methods, results, calculations and comment on Modulus of Elasticity and Modulus of Rupture. Furthermore, an investigation into how moisture content influences the strength of timber, specifically the Modulus o f Elasticity and Modulus of Rupture is included. The overall objectives were met and show that there was a correlation between density and the Modulus of Elasticity where elasticity elasticity generally improved as density increased. increased. Additionally, the composite materials, chipboard and plywood, engineered for specific structural applications were found to have elastic and maximum stress values that fell in the scope specified by the Australian Wood Panels Association. The values for the Modulus of Rupture for all specimens were determined thus allowing appropriate design for strength in terms of structural application, however direct comparison was difficult since the beam section dimensions were varied between samples.
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Table of Contents Executive Summary ................................................................................................................................. 1 List of Tables ........................................................................................................................................... 3 List of Figures .......................................................................................................................................... 3 Introduction ............................................................................................................................................ 4 1
Testing Method ............................................................................................................................... 4 1.1
Visual Strength Grading and the Effects of Defects ................................................................ 4
1.2
Three-point Flexure Testing Procedure .................................................................................. 5
2
Results ............................................................................................................................................. 6
3
Load vs. Deflection Graph ............................................................................................................... 6
4
Calculations ..................................................................................................................................... 7 4.1
Density .................................................................................................................................... 7
4.2
Moment of Inertia (mm )........................................................................................................ 8
4.3
Modulus of Elasticity ............................................................................................................... 8
4
4.3.1
Softwood ......................................................................................................................... 8
4.3.2
Hardwood ....................................................................................................................... 9
4.3.3
Chipboard ........................................................................................................................ 9
4.3.4
Plywood........................................................................................................................... 9
4.4
Modulus of Rupture (MOR) .................................................................................................. 10
4.4.1
Softwood ....................................................................................................................... 10
4.4.2
Hardwood ..................................................................................................................... 11
4.4.3
Chipboard ...................................................................................................................... 11
4.4.4
Plywood......................................................................................................................... 11
5
Evaluation of Density, Elastic Modulus & Modulus of Rupture .................................................... 11
6
The Effects of Moisture on E and MOR......................................................................................... 13
7
Applications in Building ................................................................................................................. 14 7.1
Softwood ............................................................................................................................... 14
7.2
Hardwood ............................................................................................................................. 15
7.3
Chipboard.............................................................................................................................. 15
7.4
Plywood................................................................................................................................. 16
8
Conclusions ................................................................................................................................... 16
9
Works Cited ................................................................................................................................... 17
10
Appendix A - Elastic Constants and Defect Illustrations ........................................................... 18
11
Appendix B – Australian Wood panel Association: Facts about Particleboard and MDF ......... 19 2
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12
Appendix C – Raw Data ............................................................................................................. 20
List of Tables Table 1: Visual Sample Characteristics .................................................................................................... 4 Table 2: Sample Measurements ............................................................................................................. 6 Table 3: Load Deflection Characteristics................................................................................................. 6 Table 4: Sample Densities ....................................................................................................................... 7 Table 5: Moments of Inertia ................................................................................................................... 8 Table 6: Engineering Characteristics Summary..................................................................................... 11
List of Figures Figure 1: Illustration of Three Point flexure Test .................................................................................... 5 Figure 2: Plot of Load vs. Deflection for all Samples ............................................................................... 7
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Introduction Timber from well-managed forest plantations is one of the m ost sustainable building resources available. It has a high to strength to weight ratio and is capable of transferring both tensile and compressive forces and therefore, as might be expected, is highly suitable as a flexural member (Porteous and Kermani 2007). There are a number of other distinctive characteristics that make timber an ideal construction material, these being its durability and insulating properties against heat and sound as well as its natural growth characteristics such as grain patterns and availability in many species, sizes and shapes that render it an extraordinarily versatile material (Porteous and Kermani 2007). This report provides an account of the engineering properties of four types of timber products, namely; softwood, hardwood, chipboard and plywood that are of interest to design engineers and architects. Included are particulars on visual strength grading, testing methods, results, calculations and comment on Modulus of Elasticity (E) and Modulus of Rupture (MOR). Furthermore, the report will consider how moisture content influences the strength of timber, specifically the Modulus of Elasticity (E) and Modulus of Rupture (MOR).
1
Testing Method
1.1 Visual Strength Grading and the Effects of Defects This form of grading is a manual process whereby a sample is inspected visually, since this process involves experience and personal judgment, the results are i nherently subjective. Four samples of were examined, each piece to inspect the size and frequency of specific physical characteristics or defects such as knots, slope of grain, wane, shakes and distortion, bending or twisting. The results are shown in the table 1. Table 1: Visual Sample Characteristics Sample
Visual Analysis
Softwood
Edge Grain with one knot, no other defects present
Hardwood
Edge Grain, no visual defects present
Chipboard
Visible particles, no visual defects present
Plywood
Layered appearance ( 3 layers), no visual defects present
The slope of the grain is critical when grading timber products as it can affect the strength properties of the wood as well as the type of warping which may occur under certain conditions. For i nstance boards with a straight or edge grain, as in the c ase of the above softwood and hardwood, where the board has been cut so that the fibres run up and down the length of the board will result in the greatest strength. In contrast, cross grain boards, will result in the least wood strength (Singh 2007).
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A knot, a portion of a branch enclosed by the natural growth of the tree (Porteous and Kermani 2007), found on the softwood may have had adverse effects on the mechanical pro perties of the timber sample since knots alter the fibers surrounding them, causing discontinuity and stress concentrations or non-uniform stress distributions (Mamlouk and Zaniewski 20 11). Their effects are further magnified in members subjected to tensile stress. The presence of the knot on the lower side of a member, being subjected to tensile stresses, has a greater effect on the load capacity of the member than a similar knot on the upper side being subjected to compressive stresses (Porteous and Kermani 2007). Other defects include cracks, fissures, decay and wanes, all natural defects, none of which were present in any of the test samples. The effect of a wane is a reduction in the cross-sectional area resulting in reduced strength properties due to a reduced second moment of Area (Kermani 1999). Further defects may be possible from uneven drying during the seasoning process and may result in splitting or cupping (Porteous and Kermani 2007).
1.2 Three-point Flexure Testing Procedure For each of the four timber specimens provided, softwood, hardwood, plywood and chipboard, the cross section dimensions, length and mass were recorded. The test span, distance between the supports, was also recorded. Each test specimen, in turn, was placed in the testing rig and a dial gauge placed beneath the load point of the sample, ensuring it that it just touched the underside of the sample. The dial gauge was then zeroed, and care was taken to ensure that the loading arm was not placed on the sample at this time. The loading arm was then placed on the sample and the corresponding deflection measured. The deflection was again measured in increments of 0.5 kg up to a maximum of 3.5 kg. After this point the dial gauge was removed and loading continued until failure. Using these results the Elastic Modulus (E) and Maximum Tensile Stress (or Modulus of Rupture MOR) for each samples were determined.
Point load
L = 550
Deflection (mm)
Dial Gauge
Figure 1: Illustration of Three Point flexure Test
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2
Results
Table 2: Sample Measurements
Sample
Mass (gm)
Length (mm)
Width (mm)
Depth (mm)
Softwood
65.5
749
19
11
Hardwood
42.5
600
9
9
Chipboard
170.8
750
20
16
Plywood
46.3
701
20
6
Test Span:
550mm
Table 3: Load Deflection Characteristics
Load Load (kg) 0
Softwood 0
Deflection (mm) Hardwood 0
Newtons 0
Chipboard 0
Plywood 0
0.5
4.905
1.9
2.76
1.64
9.95
1.0
9.81
2.74
3.92
2.3
14.28
1.5
14.715
3.65
4.96
2.98
18.33
2.0
19.62
4.58
6.05
3.65
22.82
2.5
24.525
5.42
7.11
4.34
26.78
3.0
29.43
6.32
8.09
5.05
31.71
3.5
34.335
7.23
9.16
5.76
36.79
Failure Load
21.5 kg (210.9N)
14.5kg (142.2N)
7.5kg (73.6N)
6kg (58.9N)
3
Load vs. Deflection Graph
The load versus deflection graphs with t he line of best fit shown for all timber samples are plotted below, care was taken to include the 0kg loads and deflections, since these points will affect the gradient of each plot. The equation of each line of best fit was used to determine the gradient, thus:
= + : : = =
() ()
=
3 48 6
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Figure 2: Plot of Load vs. Deflection for all Samples
45
40 y = 1.1162x 35
30 Softwood
) m m 25 ( n o i t c e l f 20 e D
Hardwood Chipboard Plywood Linear (Softwood ) Linear (Hardwood )
15
Linear (Chipboard ) 10
Linear (Plywood)
y = 0.2882x y = 0.2218x
5 y = 0.1778x 0 0
10
20
30
40
Load (N)
4
Calculations
4.1 Density Table 4: Sample Densities Sample Softwood
65.5
74.9
1.9
1.1
Volume (cm^3) 156.541
Hardwood
42.5
60
0.9
0.9
48.6
0.874485597
874.4855967
Chipboard
170.8
75
2
1.6
240
0.711666667
711.6666667
46.3
70.1
2
0.6
84.12
0.550404184
550.4041845
Plywood
Mass (gm)
Length (cm)
Width (cm)
Depth (cm)
Density (g/cm^3) 0.418420733
Density (kg/m^3) 418.4207332
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4.2 Moment of Inertia (mm4)
=
4
Where: I = Moment of Inertia (mm ) B = Breadth (mm) D = Depth (mm)
Table 5: Moments of Inertia
Sample
Depth (mm)
Breadth (mm)
4
I (mm )
Softwood
11.00
19.00
2107.42
Hardwood
9.00
9.00
546.75
Chipboard
16.00
20.00
6826.67
6.00
20.00
360.00
Plywood
4.3 Modulus of Elasticity
4.3.1
Softwood
: = + = 0.2218 + 0 = 0.2218 = =
=
()
=
48
3 48
0.2218 =
=
()
3
5503 48(2107.42) 5503
480.2218(2107.42)
= .
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4.3.2
Hardwood
: = + = 0.2882 + 0 = 0.2882 = =
=
() ()
48
3 48
0.2882 =
=
=
3
5503 48(546.75) 5503
480.2882(546.75)
= 4.3.3
Chipboard
: = + = 0.1778 + 0 = 0.1778 = =
=
()
=
48
3 48
0.1778 =
=
()
3
5503 48(6826.67) 5503
480.1778(6826.67)
= .
4.3.4
Plywood
: = + 9
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= 1.1162 + 0 = 1.1162 = ()
=
=
()
48
3 48
1.1162 =
=
=
3
5503 48(360) 5503
481.1162(360)
= .
4.4 Modulus of Rupture (MOR)
Load at Failure
Softwood 21.5 kg (210.9N)
Hardwood 14.5kg (142.2N)
Chipboard 7.5kg (73.6N)
Plywood 6kg (58.9N)
** Plywood sample did not rupture; deflection became too great for further consideration and thus was deemed to have failed.
=
Where: M = Bending Moment at Failure = PL/4 Y=Distance from Neutral Axis to extreme fibres = d/2 P = Load at Failure I= Moment of Inertia
4.4.1
Softwood
211 ∗ 550 11 ∗ 4 2 = 2107 = .
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4.4.2
Hardwood
142 ∗ 550 9 ∗ 4 2 = 547 = . 4.4.3
Chipboard
74 ∗ 550 16 ∗ 4 2 = 6827 = . 4.4.4
Plywood
59 ∗ 550 6 ∗ 4 2 = 360 = .
5
Evaluation of Density, Elastic Modulus & Modulus of Rupture
Abdy Kermani, in his book, ‘Structural Timber Design, 1999 states that density is the best indicator ’
when determining a timbers material properties. Such properties may include strength, stiffness, and hardness, ease of machining, fire resistance and drying characteristics. On average,
hardwood is of higher density than softwood, but there can be considerable variation in actual density in both classifications (National Association of Forest Industries 2004). A summary of the flexural characteristics of the four test samples is shown below in Table 6. Table 6: Engineering Characteristics Summary Sample
Density (gm/cm^3)
Moment of Inertia (mm^4)
Elastic Modulus (MPa)
Modulus of Rupture (Mpa)
E/ ρ Mpa/(kg/m^3)
MOR/ρ Mpa/(kg/m^3)
Softwood
0.418
2107.42
7415.39
75.7
17.74
0.181
Hardwood
0.874
546.75
21997
160.6
25.17
0.183
Chipboard
0.712
6826.67
2855.66
11.9
4.01
0.017
Plywood
0.550
360.00
8625.86
67.6**
15.68
0.122
** Plywood sample did not rupture; deflection became too great for further consideration and thus was deemed to have failed.
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The presence of moisture in timber not only increases the mass of the timber, but it also results in the swelling of the timber, and hence both mass and volume are affected. Thus, in the determination of density both the mass and volume must be determined at the same moisture content (Dinwoodie 2000). As can be observed from Table 6, the softwood possesses the lowest density, hardwood the highest with chipboard and plywood lying between. The physical substance that makes up the cell walls has a basic density of approximately 1500 kg/m3 (Dinwoodie 2000). However, as timber comprises both wood substance and voids, such as the central cavities in cells, density can vary considerably due to the cell structure between softwoods, hardwoods, different species and different trees within the same species. Since softwoods are generally faster growing, have higher moisture content and thinner cell walls, they are generally less dense when compared to hardwoods at the standard moisture content of 12 percent which is often referred to as the air-dry density (National Association of Forest Industries 2004). The Elastic modulus of the softwood sample at 7415 MPa is almost three times less than the hardwood at 21997 MPa. A study on ‘Estimation of Basic Density and Modulus of Elasticity of Eucalypt Clones in Southern China,2010’ by S.J Wu et al , found that the correlation between basic
density and the Modulus of Elasticity was significantly positive, in line with the results of this investigation where elasticity is increasing with density, disregarding plywood and chipboard which are composite materials. The Modulus of Rupture of the hardwood was significantly greater than all other specimens, while the softwood was similar to the plywood. The modulus of Rupture depends on the beam section properties and the arrangement of loading. Given that all specimens were loaded in the same manner but the section dimensions were varied, in this case it is difficult to give a straightforward comparison. The density of the Chipboard sample is relatively high as compared to the plywood and the softwood. Chipboard is a manufactured timber product whereby w ood particles are coated with a resin, then formed into a mat and pressed to produce a board of particular thickness. Chipboard is available in a range of densities which depend on type and size of wood particles used, ratio of wood particles to amount of resin and the amount of pressure used to reduce voids. Different types of boards with different engineering properties can be formed in this way (Australian Wood Panels Association Incorporated 2008). The Modulus of Rupture (MOR) is relatively low at 11.9 MPa and is close to the standard particleboard MOR as per the Australian Wood panel Association s range for ’
boards of this thickness at 15 MPa, refer to Appendix B. The chipboard in this case is not high performance and should not be used for structural applications such as flooring which requires a depth of at least 19mm and a MOR of 24 MPa. Comparatively, the Modulus of Elasticity is low at 2855 MPa, which implies that the material will reach plastic deformation relatively quickly. Since the elastic modulus is an inherent material property, it will vary with the quality and quantity of ingredients used in manufacture. Plywood is made from thinly sliced wood veneers glued together to form a board of desired thickness. The grain direction is alternated layer by layer so that the sheet has similar areas of grain in the direction of the width of the sheet and the length of the sheet (Forest & Wood Products Australia 2007). Therefore, plywood has properties that are relatively the same in both directions with regard to the plane of the sheet. Since only thin slices of timber are used in the manufacture of 12
SANDRA LISTER N7457499
this product, the size and influence of any natural characteristic is limited to the thickness of the veneer. Structural properties of plywood tend to have less variability than those for sawn t imber meaning that the mechanical properties are generally higher than the properties of the pure timber from which it was made (Forest & Wood Products Australia 2007) . In terms of this experiment, the Elastic modulus and Modulus of Rupture is comparable to that of the softwood, meaning that it may have been manufactured from timber of lesser quality than t he softwood but the manner of construction has rendered the product more stable and robust. It is important to note however, that the plywood specimen did not actually rupture at the ultimate load stated, deflection was excessive and was not longer able to be measured, and consequently specimen was deemed to have failed at this point. The Elastic modulus per unit density and Modulus of Rupture per unit density as shown in Table 6, may be useful in comparing the material flexural properties per unit mass o f a certain volume, and thus can be used to compare wood products with other materials such as Steel and Concrete. Relating these values obtained from the experiment to table 14.7 shown in Appendix A, we can see that the softwood and hardwood are approx imately in the range specified.
6
The Effects of Moisture on E and MOR
Timber properties, unlike other structural materials such as steel or concrete, are very sensitive to environmental conditions. For instance, timber is very sensitive to moisture content, which has a direct effect on the strength, stiffness and swelling or shrinkage and resistance to decay (Kermani 1999). Most timber is air dried or kiln dried to a moisture content of approximately 12% which is below fiber saturation point meaning that the cell walls are still saturated but moisture is removed from within the cells. Further reduction in moisture content will result in shrinkage, the amount of shrinkage pertaining to the particular species (Kermani 1999). Figure 3: General relationship between strength & moisture content
Kermani. A, 1999, Structural Timber Design, Chapter 1, Page 8
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Figure 3, shows the general relationship between strength of timber and its moisture content. Illustrating that there is an almost linear loss in strength and stiffness as moisture increases to approximately 30% which is consistent with the fiber saturation point (Kermani 1999). Any further increase in moisture content has no influence on strength. In terms of physical properties, it must be noted that as moisture content decreases shrinkage will increase. Seasoning is a controlled process whereby the moisture content of the timber is reduced so that it is suitable for the intended use. Seasoning defects are directly related to the movements which oc cur in timber due to changes in moisture content such as excessive or uneven drying, as well as other factors like exposure to wind and rain. Uneven drying can be caused by inferior stacking during the seasoning process and these can all produce defects in timber which ultimately reduce the strength (Porteous and Kermani 2007). However, interestingly, the level of moisture content has almost no effect on the tensile strength parallel to the grain. This strength property is determined by the strength of the covalent bonding on the molecular level. Additionally the relationship between moisture content and strength may not apply when the timber contains major defects as is the case with structural size timber for example, it has been shown that the effect of moisture content on strength decreases as the size of knots increase (Dinwoodie 2000) Timber is hygroscopic meaning that it attempts to attain equilibrium moisture content with its surrounding environment, resulting in variable moisture content. This property should always be considered when using timber, particularly softwoods which are more porous and thus more vulnerable to shrinkage and expansion than hardwoods (Kermani 1999). The strength of timber is a function of several parameters including the species type, density, size and form of members and presence of various strength reducing characteristics such as slope of grain, knots, fissures and wane. Since moisture content can affect some of these properties it will in turn affect the strength properties (Porteous and Kermani 2007). The Elastic Modulus will also deceases with increased moisture content. This variation takes place until the moisture content reaches the Fiber Saturation Point, which is around 30% for most species as shown in figure 3. It must be noted that the influence of the moisture content over the Modulus of Elasticity is not very significant (Dinwoodie 2000).
7 Applications in Building 7.1
Softwood
When compared to hardwoods, plantation softwood timber is less variable and thus, more predictable as a raw material. It also provides larger yields of usable timber in a shorter timeframe. Softwood dries quickly, is easily machine-processed, forms strong gluing bonds and is easy to treat with preservatives for uses where durability is important (Willmott forests Limited 2011). These properties make softwood extremely versatile, due it good strength to weight properties is suitable for many applications such as, structural sawn timber, laminated beams and veneer lumber, Pine poles, piles and fence posts and landscaping uses such as retaining walls. Its light colour, even texture and low resin content also make it suitable for wood panels, such as Medium density 14
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fiberboard (MDF) as well as wide range of Pulp and Paper products. Residues of wood chips, shavings and sawdust from the production of solid wood products are also a good source for these products (Willmott forests Limited 2011).
7.2 Hardwood Different species of hardwood afford themselves to a varied range of uses mainly due to the variety of characteristics apparent in different timbers including, density, grain, pore size, growth pattern, wood fiber pattern and flexibility. Hardwood with good strength characteristics lends itself to structural applications where strength is a critical factor such as bearers, joists, lintels and roof beams (Timber Development Association 2011). Other suitable structural applications for some hardwoods may be small temporary bridges, wharf timber or timber for use in wet conditions given that it is generally less porous than soft woods. Additional uses for hardwoods may be pre-assembled trusses and frames for large structures and other smaller objects such as furniture and musical instruments. Timbers for structural applications where large loads may occur would need to be specially selected and well graded (Timber Development Association 2011).
7.3 Chipboard The Australian Standard AS/NZS 1859.1-2004 describes three types of Chipboard otherwise known as particleboard, and each is engineered for specific structural applications. Standard general purpose particleboard intended for internal use in dry conditions, such as in the construction of furniture, cupboards and shelving. Moisture resistant general purpose particleboard is intended for internal where humid conditions are present or where occasional wetting may occur. It is however, not moisture proof and should not be used where there is persistent wetting the particleboard is likely to degrade via adhesive failure and is prone to fungal attack. Continued Exposure of particleboard to the weathering will have an effect on its internal bonding strength and stiffness (Australian Wood Panels Association Incorporated 2008). High Performance particleboard is engineered for use in continuously humid conditions and load bearing applications in dry and humid conditions. Chipboard can also used for flooring; there are two classes in this case, specifically Class 1 and Class 2 Flooring Board. Class 1 is stronger and is used for most internal flooring and is manufactured with an adhesive which does not deteriorate i n the presence of moisture. Class 2 is only suitable indoors where there is no risk of dampness such as upper storey floors (Timber Development Association 2011).
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7.4 Plywood Plywood is designed to have high strength and stiffness to weight ratios which renders it suitable for installation very cost effective in applications such as residential and commercial flooring, shearwalls and diaphragms, formwork and webbed beams (Forest & Wood Products Australia 2007). The cross-laminated construction of plywood ensures that sheet sizes remain r elatively stable under changes of temperature and moisture, making it particularly suited to formwork applications. The shear strength, approximately double that of solid timber due to its cross laminated structure, makes it suitable for use in gussets for portal frames, webs of fabricated beams a nd thin plywood bracing panels (Forest & Wood Products Australia 2007). Plywood, as with most timber products, has the ability to accommodate the occasional short term load up to twice the design load. This property is beneficial for applications such as loading docks where short term vehicle impact can be expected or in buildings subject to seismic activity or cyclonic winds. Plywood may also be utilized as interior panelling; decorative plywoods are frequently used as internally for their aesthetic value (Forest & Wood Products Australia 2007).
8
Conclusions
This report has provided an account of the flexural properties of four types of timber products, namely; softwood, hardwood, chipboard and plywood that are of interest in terms of structural design. It was found that the softwood had the lowest density, hardwood the highest with chipboard and plywood lying between. The test and research demonstrated that there was a correlation between density and the Modulus of Elasticity where elasticity generally improved as density increased. The composite materials, the chipboard and plywood, engineered for specific structural applications were found to have elastic and maximum stress values that fell in the scope specified by the Australian Wood Panels Association. The values for the Modulus of Rupture for all specimens were determined thus allowing appropriate design for strength in terms of structural application, however direct comparison was difficult in this case since the beam section dimensions were var ied. An overview of the effects of defects on Strength and structural applications for all specimens as well as brief outline visual grading and effects of Moisture of timber was also incorporated.
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9
Works Cited
Australian Wood Panels Association Incorporated. Facts about Particleboard and MDF. Coolangatta: Australian Wood Panels Association Incorporated, 2008. Dinwoodie, J M. Timber Its Nature and Behaviour. New York: Spon Press, 2000. Forest & Wood Products Australia. “Plywood.” Timber.org.au. 2007.
http://www.timber.org.au/ntep/menu.asp?id=104 (accessed May 13, 2011). Kermani, Abdy. Structural Timber Design. Oxford: Blackwell Publishing , 1999. Mamlouk, Michael S, and John P Zaniewski. Materials for Civil and Construction Engineers. New Jersey: Pearson, 2011. McKenzie, William M C, and Binsheng Zhang. Design of Structural Timber to Eurocode 5. New York: Palgrave Macmillan, 2007. National Association of Forest Industries. Timber Species and Properties: Timber Manual Datafile 1. Sydney: National Association of Forest Industries, 2004. Porteous, Jack, and Abdy Kermani. Structural Timber Design to Eurocode, 5. Oxford: Blackwell Publishing, 2007. Singh, Harbhajan. Design of Masonry and Timber Structure. Chandigarh: Abhishek Publications, 2007. Timber Development Association. “Structural Timber.” Timber.net.au. 2011.
http://www.timber.net.au/index.php/Structural-Timber.html (accessed May 13, 2011). Willmott forests Limited. “About the Softwood Industry.” Willmott Forests. 2011.
http://www.willmottforests.com.au/default.asp?id=about_the_softwood_industry (accessed May 13, 2011).
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10 Appendix A - Elastic Constants and Defect Illustrations
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11 Appendix B – Australian Wood panel Association: Facts about Particleboard and MDF
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12 Appendix C – Raw Data
Sample
Mass (gm)
Length (mm)
Width (mm)
Depth (mm)
Softwood
65.5
749
19
11
Hardwood
42.5
600
9
9
Chipboard
170.8
750
20
16
Plywood
46.3
701
20
6
Test Span:
550mm
Load Load (kg) 0
Softwood 0
Deflection (mm) Hardwood 0
Newtons 0
Chipboard 0
Plywood 0
0.5
4.905
1.9
2.76
1.64
9.95
1.0
9.81
2.74
3.92
2.3
14.28
1.5
14.715
3.65
4.96
2.98
18.33
2.0
19.62
4.58
6.05
3.65
22.82
2.5
24.525
5.42
7.11
4.34
26.78
3.0
29.43
6.32
8.09
5.05
31.71
3.5
34.335
7.23
9.16
5.76
36.79
Failure Load
21.5 kg (210.9N)
14.5kg (142.2N)
7.5kg (73.6N)
6kg (58.9N)
20
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