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In this paper, composites based on unsaturated polyester resin reinforced with short Alfa fibers are studied in detail. Alfa fibers have been previously treated with various concentrations NaOH (1, 3, 5, 7%) during 24 h. The influence of alkali treatment on fiber morphology is analyzed. Analysis by FTIR and X-ray diffraction showed physico-chemical changes in Alfa fiber treated surfaces. SEM observations also helped to highlight these changes. The results of static tests on composites showed improvements in tensile and flexural strengths of composites reinforced with the treated fibers, particularly the composite with treated fibers at 7% NaOH. These improvements were about 30% and 50%, respectively, compared to untreated fiber reinforced composite.

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In the present work, the influence of MgO addition and sintering parameters on the formation and densification of mullite was investigated. The morphology of powders and the microstructure of the sintered samples were characterised by means of a scanning electron microscope. X-ray diffraction was used to characterise phases formed in sintered samples. The density of sintered samples was measured using a densimeter and quantified according to the Archimedes principle. MgO was added at 1, 2, 3, 4, 5 and 6 wt-% to kaolin and alumina and the powders were ball milled for 5 h then uniaxially compacted at 75 MPa and finally sintered at 1500, 1550, 1600 and 1650uC for 2, 4, 6 and 8 h. It was found that addition of MgO not only affected mullite formation but also promoted grain growth. For samples containing 0, 1 and 2 wt-%MgO only mullite was formed. While, in addition to mullite, Al 2 O 3 was present in sample containing 3 wt-%MgO. At higher MgO content (4, 5 and 6 wt-%), three phases, i.e. mullite, Al 2 O 3 and spinel, were formed. Addition of 1 wt-%MgO increased the density of all samples for all sintering times and higher densities corresponded to higher sintering temperatures. At higher MgO content, higher temperatures led to lower densities and lower temperatures led to higher densities for almost all sintering times.

In recent years, natural fibres have been experimented to replace glass fibres in reinforcing thermosetting polymer. Since the interfacial adhesion between the raw natural fibres and the polymer matrix are often not adapted to the intended applications, the fibre surface most often requires a preliminary chemical modification. The fibres which were extracted from the Arundo donax L. Plant (called cane fibres), are little studied in the literature of fibre/polymer composites. In the present work, the cane fibres have been treated at constant soaking time with 2-8% NaOH aqueous solutions for 24 h. The composite reinforced by 6% NaOH-treated cane fibres, exhibited maximum improvements in tensile and flexural strength by 57% and 45% respectively. A combination of Fourier transform infrared, scanning electron microscopy, X-ray diffraction and moisture absorption techniques has been used for material characterisation. The crystallinity index yields information about fibre modification by NaOH. Such cane fibre composites could become an alternative to existing materials, with interesting tensile and flexural strengths, low cost and less ecological impact.

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