Effect of hygrothermal treatment on the tensile properties - ethesis ...

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The matrix <strong>of</strong> the untreated sample shows no damage. In contrast, the <strong>hygrothermal</strong>ly treated samples show damage in their matrix. A crack is formed at the fibre-matrix, which leads to debonding at the interface, and finally fibre pullout occurs. 100 0 C Fig. 4.8: Fibre region <strong>of</strong> untreated and 16 hours <strong>hygrothermal</strong>ly treated sample The untreated samples do not show any sign <strong>of</strong> fibre pull-out. The failure <strong>of</strong> the composite may be attributed to the failure <strong>of</strong> matrix. There are some signs <strong>of</strong> fibre breakage in the above figure in the case <strong>of</strong> <strong>hygrothermal</strong>ly conditioned samples. Mositure adsorbed onto the matrix and fibre can be seen. Fig. 4.9: Matrix cracking <strong>of</strong> untreated and 16 hours <strong>hygrothermal</strong>ly treated sample The failure in case <strong>of</strong> 100 0 C hot pressed samples is due to matrix cracking. The loss <strong>of</strong> toughness due to complete curing <strong>of</strong> the unsaturated polyester resin doesn’t provide enough time for the transfer <strong>of</strong> load from matrix to fibre. The matrix behaves as a 34
igid material and the crack in the matrix doesn’t get opportunity to blunt the tip resulting in loss <strong>of</strong> strength. The degradation is more when the sample is <strong>hygrothermal</strong>ly conditioned for 16 hours. The loss <strong>of</strong> material and the crack in the matrix is clearly visible in the above figures. The reason for fibre pullout in most <strong>of</strong> the sample in contrast to fibre breakage can be ascertained to the fact that the bonding between the fibre and the matrix at the interface is weak. Hydroxyl groups(-OH) in the main backbone chain <strong>of</strong> a resin provide sites for hydrogen bonding to the surface <strong>of</strong> the natural fibres, which contain many hydroxyl groups in their chemical structure. Thus, polyester resins, having no hydroxyl group in its backbone chain generally has the weakest bonding, hence the lowest adhesive properties compared to other resins. 35
Page 1 and 2: EFFECT OF HYGROTHERMAL TREATMENT ON
Page 3 and 4: ACKNOWLEDGEMENT I avail this opport
Page 5 and 6: CONTENTS Chapter 1 INTRODUCTION 1 1
Page 7 and 8: 1. INTRODUCTION 1.1 Introduction Th
Page 9 and 10: - Reduced fogging behaviour. - Pric
Page 11 and 12: 2. LITERATURE REVIEW 2.1. Natural f
Page 13 and 14: seen as degree or the homogenity or
Page 15 and 16: alternate acid and glycol units. Th
Page 17 and 18: 2.7. Hygrothermal Effect</s
Page 19 and 20: degradation. While in some cases a
Page 21 and 22: 3. EXPERIMENTAL WORK � 3.1. Prepa
Page 23 and 24: Chapter 4 RESULTS AND DISCUSSION 23
Page 25 and 26: In the above table, data obtained f
Page 27 and 28: weak and the fracture is due to the
Page 29 and 30: Fig. 4.2: Displacement at break <st
Page 31 and 32: 4.2. Hygrothermal Behaviour:- Table
Page 33: The figure shows shows swelling due
Page 37 and 38: 5. CONCLUSION • Hot pressing <str
Page 39 and 40: REFERENCES 1. Mohanty A K, Misra M,

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