Abstract
From the experiment, the problem encountered was to find the
compression and tension properties of solid woods, specifically
hardwood, medium wood and softwood. To overcome this problem we had
done several experiments to find the required characteristics and
thus be able to summarize its compression and bending properties.
From the result, for the bending properties of wood, the average
MOR of softwood is about 71.81 MPa, with an MOE of about 8535.16
MPa. The average MOR of hardwood meanwhile is about 89.16 MPa,
while its MOE is 11305.90 MPa. On the compression properties of
solid wood, hardwood showed a higher resistance to compression than
medium wood, as it is able to withstand a considerably higher load
during compression. Hardwood also showed a higher stress value
compared to those of medium wood samples.
Introduction
Solid wood as we know can be namely be classed as hardwood,
medium, and softwood according to its density. The purpose of these
experiments is to find the compression and bending properties of
these woods according to its density, whether it is the same or
vice-versa. The main experiment being done is the 3-point flexurial
test which we put load/force on 3 points on the speciments. The
results were being calculated by the computer and analyzed.
Compression and bending properties are very important to know and
analyzed because we can know what type, densities, and pressure
these woods can applied and withstand on the actual real life,
mostly in the engineering and construction fields.
Bend or flexure testing is common in springs and brittle
materials whose failure behaviours are linear such as concretes,
stones, woods, plastics, glasses and ceramics. Other types of
brittle materials such as powder metallurgy processed metals and
materials are normally tested under a transverse flexure. Bend test
is therefore suitable for evaluating strength of brittle materials
where interpretation of tensile test result of the same material is
difficult due to breaking of specimens around specimen gripping.
The evaluation of the tensile result is therefore not valid since
the failed areas are not included in the specimen gauge length.
Materials & Method
Bending test
Materials:5 (60x 20) cm softwood specimens, 5 (60x20) cm
hardwood specimens, Instron Lab machine, Vernier caliper, Weight
balance, Circular-saw, Ruler.
Method:1. Measure the width and thickness of the specimen
including the span length in the table provided for the calculation
of the stress and elastic modulus. Mark on the locations where the
load will be applied under three-point bending.2. Bend testing is
carried out using a universal testing machine until failure takes
place. Construct the load-extension or load-deflection curve if the
dial gauge is used.3. Calculate the bend strength, yield strength
and elastic modulus of the specimen4. Describe the failure under
bending and sketch the fracture surfaces in the table provided.5.
Discuss the obtained experimental results and give conclusions.
Compression test
Materials:5 (60x 20) cm softwood specimens, 5 (60x20) cm medium
wood specimens, Instron Lab machine, Vernier caliper, Weight
balance, Circular-saw, Ruler. Method:1. Dimensions of test piece
are measured at 3 different which is width, thickness and length.2.
Ends of the specimen should be plane. For that the ends are tested
on a bearing plate.3. The specimen is placed centrally between the
two compression plates, such that the center of moving head is
vertically above the center of specimen.4. Load is applied on the
specimen by moving the movable head.5. Load is applied until the
specimen is failed or the line of graph is dropped.
Bending Test Results
1. Hardwood
2. Softwood
Graph 1. Hardwood
2. Softwood
Compression testResults 1. Softwood
2. Hardwood
Graphs1. Softwood
2. Hardwood
Discussion
Bending
From the results that have been taken, it is known that the
average or mean for MOR of hardwood is about 87.16. From the
specimens, the highest recorded MOR is taken from sample 1 with an
MOR of 110.93, while the lowest from these hardwood samples is from
the sample 3 with an MOR of 46.58. The standard deviation of the
samples is calculated and the result is about 25.66. From the load
table, it can be seen that the average load applied until breaking
point reached is about 2065.69 N. The highest load being put is at
sample 1 at about 2753.94 N, while the least amount of load needed
to reach bending limit is on sample 3 at 1080.36 N. The standard
deviation of the loads is about 622.58 N.
For the softwood samples, the results of the testing is observed
and compared with the hardwood. For the softwood, the average or
mean MOR for 5 samples is about 71.81 MPa, with the highest
recorded MOR is achieved at sample 3 at 78.31 MPa. The lowest MOR
of softwood is recorded at 63.45 MPa for sample 2. The standard
deviation of these MOR is calculated and the result is about 6.02
MPa. As for the loads, the average load being applied to the sample
until it achieves breaking point is about 1556.54 N, with the most
loads being applied at sample number 3 with 1810.33 N. The least
load applied on the sample meanwhile is about 1391.52 N for sample
5. The standard deviation of the loads is calculated and the result
is about 203.11 N.
From these results, we can see that the MOR of hardwood is
higher than those of softwood, with the difference in average MOR
is about 15.35 MPa. This value is quite significant considering the
sample are of the same dimensions, albeit different type. Besides
that, the results also show that hardwoods are much greater in
terms of tensile strength than softwood, as it can withstand much
more loads and force until it breaks apart. The reason for these
results are shown may be due to the structure of the hardwood and
softwoods, with the hardwood may had a more turgid and compact
cells than softwood, besides not having much pores in the cell
components of the wood.
Compression
For the compression test, in softwood, the results show that the
mean or average maximum load for the samples is about 15.76 kN.
From the samples also, the maximum load it achieves is 17.84 kN for
the sample 1, while the least maximum load is achieved at sample 2,
with a load of 14.28 kN. At these maximum loads, the extension of
the sample (linear) was also calculated and the result is shown as
in table. The result for the extension shows that the average
extension for these samples is about 1.59 mm, with its standard
deviation is valued at 0.23 mm. For the stress results, the highest
maximum stress achieved between the samples is recorded at sample
1, with a maximum stress of 14.53 MPa. The average or mean maximum
stress for these samples is about 13.33 MPa, while the standard
deviation for stress is about 0.87 MPa.
For the hardwood compression test, the highest maximum load is
achieved during sample 2 when 26.56 kN of force is applied onto it,
while the least maximum load is recorded at 24.13 kN for sample 5.
In all, the average load among these samples is recorded as 25.39
kN, with the standard deviation of 1.04 kN. For the linear
extension, the highest extension at maximum load is achieved at
sample 2 with 1.88 mm, when the maximum load is about 26.56 kN.
Meanwhile, the least extension happens at sample 5, with 1.51 mm
only. On average, the extension at max load is about 1.67 mm, with
a standard deviation of 0.15 mm. Move on to the stress table, the
maximum stress achieved on average between these samples is about
64.91 MPa, with the highest max stress recorded at sample number 2
with a stress of 68.02 MPa.
From these results, we can see that the average maximum load for
hardwood is considerably higher than those of softwood; with the
difference between these 2 types is about 9.63 kN. Also the average
stress applied on the solid woods is much higher for those of
hardwood, with the difference between their average stress of
hardwood and softwood is about 48.73 MPa. This means that hardwood
is more resistance to compression than softwood due to their
properties and density, and because of that, they are able to
withstand such high stress/force during compression test.
Conclusion
In the world of cellulosic materials, hardwoods as we know it
are trees that are angiosperms. This means that they produce seeds
which have a protective covering such as fruit or a seed with a
shell. Softwoods are determined by their seeds also. Trees which
are softwood are called gymnosperms and they are determined as
having seeds which do not have any sort of protective covering
whatsoever. Most people believe that a hardwood will be denser than
softwood and, although this is often the case, it is not always a
true statement. For instance, there is a wood known as balsa wood
which is one of the lightest woods around. It is highly pliable and
is one of the lowest density woods available, but, it is still
considered to be a hardwood because it comes from an angiosperm
tree.
For the conclusion, we can conclude that hardwood is more
superior to lightwood in term of MOE and MOR. They are more
resistant to load and are able to withstand a large amount of force
in compression and also bending. This is because they are different
in density. Hardwood also has a higher density and is therefore
usually harder and softwood has a lower density, therefore most
softwood varieties are softer than hardwood.
Reference
1. Dr. Dinwoodie (2000) Timber : Its nature and behavior. 2nd
Edition; CRC Press.2. R.C. Hibbeler (2011) Mechanics of materials
8th Edition ; Prentice Hall.3. Peter Domone. (2010) Construction
Materials ; CRC Press 4th Edition.4. A.A. Moslemi (1974)
Particleboard : Technology. Southern Illinois University Press.5.
http://www.mida.gove.my6.
http://en.wikipedia.org/wiki/Particle_board
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