Dissertations in Forestry and Natural Sciences

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Taneli Väisänen: Effects of Thermally Extracted Wood Distillates on the Characteristics of Wood-Plastic Composites stresses can be induced when the specimen is centered in the grips or when the clamping pressure is applied. The maximum allowable pre-stress must be less than 1% of the measured stress results. The induced strain value must be less than 0.05%, accordingly. ASTM D638-14 does not contain these specifications, and therefore, it lacks the defined status of the stress after placing the specimen in the grips. Thus, the corrected strain zero point is defined as the point where the linear slope of the stress-strain curve crosses the strain axis. This correction can exert a significant effect on the measured tensile modulus. In ISO 527-1, the point where the tensile modulus is measured is precisely defined whereas the definition of tensile modulus in ASTM D638-14 is based on the corrected strain zero point. If the material lacks the linear region in the stress-strain curve, the modulus is determined from a secant modulus that is determined between the corrected strain zero point and a freely selected point on the curve. Consequently, this may result in significant variations between the results carried out according to ISO or ASTM standard. Another difference between these standards is related to the test speed used in determining tensile modulus. In ISO 527-1, the tensile modulus is measured with the lower test speeds than tensile strength, but the same test speeds are allowed to be used throughout the test in ASTM D638-14. There are also differences in the requirements for extensometers; ISO 527-1 allows the lower measurement uncertainty than ASTM D638-14. 3.1.2 Flexural strength and modulus The material’s ability to resist deformation under load is defined as the flexural strength, which is typically measured using a three- or four-point flexural test technique. During the test, the sample experiences many kinds of stresses throughout its depth. At the outside of the bend, the stress is tensile in its nature whereas at the load-bearing side, the sample experiences compressive stress (Sain and Pervaiz 2008). Usually most of the materials fail under tensile stress rather than compressive stress, meaning that the maximum tensile stress value that the material 52 Dissertations in Forestry and Natural Sciences No 222
Characterization of wood-plastic composites can withstand before breaking is its flexural strength. Mathematically, the formula to calculate the maximum surface stress, S, for a rectangular sample in the three-point bending test is expressed as: S = 3FL s 2bd s 2 , (3.3) where F is the bending load (N) at the given point, Ls is the length of span (mm), b is the width of the sample (mm), and ds is the thickness of the sample (mm). In ISO 178, Ls is recommended to be 64 mm. Flexural modulus, E, is the ratio of stress to strain within the elastic region. It is computed from the slope of a stress-strain curve (Figure 8) obtained from the flexural strength test. The flexural modulus for the three-point test of a rectangular sample can be expressed as: E = L s 3 F 4bh 3 d , (3.4) where h is the height of the sample (mm) and d is the deflection (mm). The test parameters for flexural testing are defined differently in ASTM D790-15 and ISO 178 since the dimensions of the specimen are also different. In addition, the point where the test is stopped is not the same. In ASTM D790-15, the test is stopped when a 5% deflection is reached or if the specimen breaks this value. In ISO 178, the test continues until the specimen breaks. If the specimen does not break, the stress at 3.5% strain is reported. Consequently, these standards provide different results if the specimen strain is higher than 3.5%. 3.1.3 Impact strength Impact strength can be determined using either the Charpy or Izod impact test. Although the principle of these tests is similar, there are some differences in the testing procedures. In Charpy impact test, a specimen with dimensions of 4.1 mm × 10.1 mm × 55 mm is positioned horizontally in the middle of two supports. Dissertations in Forestry and Natural Sciences No 222 53
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PUBLICATIONS OF THE UNIVERSITY OF E
Page 4 and 5: Grano Oy Jyväskylä, 2016 Editors:
Page 7 and 8: ABSTRACT The use of raw materials d
Page 9: Universal Decimal Classification: 6
Page 12 and 13: Finally, I am grateful to my wife A
Page 14 and 15: TD-GC-FID/MS Thermal desorption/gas
Page 17 and 18: LIST OF ORIGINAL PUBLICATIONS This
Page 19 and 20: Contents 1 Introduction ...........
Page 21 and 22: 1 Introduction The finiteness of cr
Page 23 and 24: Introduction A new and environmenta
Page 25 and 26: 2 Wood-plastic composites By defini
Page 27 and 28: Wood-plastic composites additives u
Page 29 and 30: Wood-plastic composites Cellulose i
Page 31 and 32: Wood-plastic composites The propert
Page 33 and 34: Wood-plastic composites Figure 3. T
Page 35 and 36: Wood-plastic composites of lubrican
Page 37 and 38: Wood-plastic composites roughness a
Page 39 and 40: Wood-plastic composites Hosseinaei
Page 41 and 42: Wood-plastic composites the accessi
Page 43 and 44: Wood-plastic composites However, WP
Page 45 and 46: Wood-plastic composites A typical s
Page 47 and 48: Wood-plastic composites to fill the
Page 49: Wood-plastic composites absorption.
Page 52 and 53: Taneli Väisänen: Effects of Therm
Page 63 and 64: 4 Thermal processing of wood Therma
Page 65 and 66: Thermal processing of wood Figure 9
Page 67 and 68: Thermal processing of wood counterp
Page 69 and 70: Thermal processing of wood and the
Page 71 and 72: Thermal processing of wood and Miet
Page 73 and 74: 5 Aims and significance Despite the
Page 75 and 76: 6 Materials and methods Two types o
Page 77 and 78: Materials and methods heat energy f
Page 79 and 80: Materials and methods with the untr
Page 81 and 82: Materials and methods 6.2.1 Tensile
Page 83 and 84: Materials and methods 6.3 WATER ABS
Page 85 and 86: Materials and methods The emissions
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Taneli Väisänen: Effects of Therm
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9 Summary and conclusions In the pr
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Bibliography Abdolvahaba E, Lashgar
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Bibliography Ayrilmis N, Jarusombut
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Bibliography Cernansky R. State-of-
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Bibliography polypropylene composit
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Bibliography with odor assessments
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Bibliography La Mantia FP, Morreale
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Bibliography Mohan D, Pittman CU, a
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Bibliography Rinne J, Taipale R, Ma
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Bibliography Stark NM and Rowlands
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Bibliography Yeh S and Gupta RK. Im
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