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The main aim of this work was to study the effects of chemical treatments on veldt grape fibers (VGFs) and their composites with unsaturated polyester (UP) as the matrix. Alkalis such as sodium hydroxide (NaOH) and calcium hydroxide [Ca(OH) 2 ] and silane coupling agent (NaOH 1 silane) were used to modify the surface of optimally selected 40mm long fibers. The chemical treatments were carried with different concentrations of 5%, 10%, and 15% of chemical agents for 1 h. The chemically treated single fibers were subjected to tensile testing. The chemical analysis, crystallinity and functional group identification of both untreated and surface modified VGFs were carried out. The untreated and chemically treated 40 mm fiber length VGFs/UP composites were prepared with a loading of 40 wt% for studying the mechanical properties. The enhanced tensile strength of VGFs was found at the optimized concentration of 10% (NaOH), 15% [Ca(OH) 2 ] and 10% (NaOH 1 silane) for various chemical treatments. The thermal stability of treated VGFs was higher when compared to untreated ones. Among all, the Ca(OH) 2 treated VGF/UP composites possessed better mechanical properties. Scanning Electron Microscopic (SEM) analysis was performed to identify the failure mechanism for the impact fractured samples.

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Bending, buckling and free vibration behaviors of functionally graded (FG) carbon nanotube (CNT)-reinforced polymer composite beam under different non-uniform thermal loads have been analyzed using finite element method. Extended rule of mixture is used to obtain effective material property of the composite. Four different types of FG beam exposed to four different assumed one-dimensional temperature distributions along the length of the beam are analyzed. Parameters studies are carried out to investigate influences of the volume fraction of the carbon nanotube, functional grading and the nature of temperature variation on bending, buckling and free vibration characteristics. It is found that bending deflection reduces with increase in volume fraction of the CNT except for unsymmetrical functional graded beam. The static bending deflection and deformed shape of the beams are significantly influenced by the nature of temperature field. The critical buckling temperature of the beam with symmetric CNT distribution (where CNTs concentration is far from the neutral axis) is greater than other beams under different temperature fields and its value is less when the beams are exposed to uniform temperature rise above ambient temperature compared to other non-uniform temperature variations. However, the critical buckling temperature is not increasing significantly with increase in volume fraction of the CNT. The fundamental buckling mode shape is not sensitive to the nature of temperature variation but bending amplitude of the buckling mode shape is significantly influenced by functional grading of CNT and volume fraction of the CNT. The natural frequency of the beams reduces significantly with increase in temperature and the free vibration mode shapes are not influenced by temperature rise, nature of temperature variation and volume fraction of the CNT.

The morphological, physicochemical, mechanical and thermal properties of Veldt-grape stem fibre and wild date palm leaf stalk fibre are described in this work, which are seldom studied before. The botanical name of Veldt-grape stem fibre and wild date palm leaf stalk fibre are known as Cissus quadrangularis and Phoenix reclinata, respectively. The morphological analysis of vegetable fibres showed the presence of cracks, microvoids and impurities on the surfaces of Veldt-grape stem fibre and wild date palm leaf stalk fibre. Veldt-grape stem fibre possessed the lowest diameter and density of approximately 0.2668 mm and 1.2128 g/cm 3 , respectively, compared to wild date palm leaf stalk fibre. An X-ray diffraction and Fourier transform infrared analysis of Veldt-grape stem fibre and wild date palm leaf stalk fibre exhibited the presence of cellulose I b with a crystallinity index of 30.9% and 38.8%, respectively. Wild date palm leaf stalk fibre contained high surface roughness in the range of 0.904 mm than Veldt-grape stem fibre (0.611 mm). Tensile tests displayed that wild date palm leaf stalk fibre has highest tensile strength of around 66 MPa, and Veldt-grape stem fibre has highest strain to failure of around 6% in comparison with other fibre. The thermogravimetric analysis indicates that thermal stability of Veldtgrape stem fibre and wild date palm leaf stalk fibre is better up to 230 C and 250 C, respectively, which are well within the polymerisation process temperature.

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