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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