ABSTRACT
In this work,theproperties of short okra-glass fibers reinforced epoxy hybrid composites were studied. Critical fiber length of the okra fiber was studied at different lengths (10mm, 20mm, 30mm, 40mm and 50mm). Fiber length of 20mm exhibited the best optimal property values. The properties obtained were Tensile strength value of 10.7MPa, MoE value of 698.8MPa, impact strength of 20kJ/m2, hardness of 39.7HRF and the least water absorption capacity of 4.3%.Based on these results, 20mm was selected as the critical length of the okra fiber. Hybridization of okra fiber with the glass fiber was based on the established 20mm length of okra fiber. The best hybridization ratio of okra:glass was determined by varying the hybrid ratio (90:10, 80:20, 70:30, 60:40 and 50:50). The 50:50 okra:glass ratio was observed to have the best tensile strength value of 12.4MPa, MoE of 752MPa, elongation and energy at break values of 2.5mm and 4.6J, impact strength of 27.8kJ/m2, hardness of 56.8HRF and the least percentage water absorption capacity of 2.6%. To improve on the properties of the composite, the okra fiber was treated with varying concentrations of NaOH solution (5%, 10%, 15% and 20%) to determine the best treatment concentration. The result showed that the 10% concentration treated fiber composite exhibited the best tensile strength, elongation at break, MoE, hardness and energy at break with values of 24.5MPa, 29mm, 786MPa, 68.6HRF and 5.8J respectively. The 5% concentration treated fiber composite exhibited the highest impact strength, flexural modulus (MoR) and the least water absorption with values of 64.3kJ/m2, 50.4MPa and 1.9% respectively.
CHAPTER ONE
INTRODUCTION
1.1 PREAMBLE
Hybrid composites involve two or more types of fibers set in common matrix (Dixit and Verma, 2012). The particular combination of fiber is usually selected to balance strength and stiffness, provide dimensional stability, reduce cost, reduce weight or improve fatigue and fracture resistance (Moriteiro et al., 2005). The idea of hybrid fiber reinforced composite has been researched for a series of material combination. Hybridization ofcomposites made of natural fibers and synthetic fibers, can improve the properties of the natural fiber reinforced composite significantly (Mubarak et al., 2009).
The potential advantages of combining two kinds of fiber in a singlepolymer matrix have been described by many researchers. Jawaid and Abdul Khalil (2011)reported that the behaviour of hybrid composites appeared to be simply aweighted sum of the individual components in which there is a more favourable balance between the inherent advantages and disadvantages. While using a hybrid composite in which two or more types of fibers are employed, the advantages of one type of fiber could compliment what the other hybridized fiber lacks (Maya and Thomas 2008).
It is generally accepted that the properties of hybridcomposites are controlled by many factors such as the nature of matrix, nature of the fiber, hybriddesign,length and relative composition of the individual fibers, the fiber-matrix interface bonding, arrangement of both the fibers and also on the failure strain of individual fibers (Sreekalaet al., 2002).
