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.

Composite materials based on Alfa fibers and unsaturated polyester resins were manufactured by the hand layup technique. Mechanical properties of composites prepared form Alfa fibers collected from the region of Boussaada (Algeria), treated by various concentrations of NaOH solutions (1, 3, 6, 9, and 12%) during 24 h were found to be better than those of the untreated ones. The 6% NaOH-treated fibers composite showed maximum improvement in tensile strengths about 63% and the 9% NaOH treated fibers composite showed maximum improvement in flexural strength about 52%, respectively. The tensile modulus improved by 50.48%. The flexural modulus was also improved by 44.06% compared to the untreated Alfa fiber composite. FTIR characterization of Alfa fibers showed that the number of hydroxyl groups (OH) decreased and the crystallinity index increase by 16.60% after alkaline treatment. SEM observations on fibers' surfaces showed that the alkaline treatment improved the interface adhesion of fiber-matrix.

This study investigates the effect of the chemical treatment of sawdust on the mechanical and thermal properties of a clay composite reinforced with sawdust in variable mass proportions: 0.5, 1, 1.5, 2 and 2.5%, intended for use as brick in rural houses in desert areas. The sawdust was chemically treated with 5 wt% NaOH and 0.01 wt% KMnO4 solutions. The mechanical test results of the reinforced composite with alkali-treated sawdust show an increase in flexural and compression strength, reaching a maximum value of 0.89 and 4.85 MPa, respectively. However, the thermal test results show a significant decrease in the thermal conductivity of the sawdust-reinforced composite. The best result recorded is that of untreated sawdust, which has a value of 0.37 (W.m−1.K−1) compared to the one reinforced with treated sawdust.

Ce travail s'inscrit dans le développement de matériaux locaux, telle que la fibre végétale (fibre de palmier) et l'argile rouge du sud Algérien, largement utilisées dans la préparation des briques, comme matériaux de construction rurale. Les fibres végétales possèdent des propriétés très intéressantes, elles sont : renouvelables, biodégradables et le rapport coût/légèreté faible. Leurs propriétés mécaniques sont très importantes. Cependant, le problème prédominant dans ce type de matériaux composites est la faible adhésion de l'interface matrice-fibre, attribuée probablement, à la nature de la surface et au caractère hydrophobe des fibres naturelles, conduisant ainsi, à des propriétés mécaniques faibles pour le composite envisagé. Le but de cette étude consiste à traiter la fibre de palmier par une solution basique d'hydroxyde de sodium (NaOH 4 % [m/v]) durant des périodes variables : 3, 7, 24 et 48 heures, afin d'améliorer l'adhésion interfaciale. Les résultats obtenus à partir des essais réalisés sur le composite renforcé par les fibres de palmier traitées durant 7 h ont montré une nette augmentation quant à la résistance, à la flexion et à la compression ; cette croissance est respectivement de l'ordre de 57 et 60 %, comparativement au composite renforcé par les fibres non traitées. On peut déduire que les fibres de palmier peuvent être considérées comme l'un des matériaux appropriés pour le renforcement de l'argile.Mots clés : fibres de palmier / argile rouge / traitement alcalin / composite Abstract. Study of the effect of alkaline palm fiber treatment time on the mechanical behavior of red clay materials from the region of M'sila. This work is part of the development of local materials, such as vegetable fiber (palm fiber) and red clay from southern Algeria, widely used in the preparation of bricks as rural building materials. Vegetal fibers have very interesting properties, they are: renewable, biodegradable and low cost / lightness ratio. Their mechanical properties are very important. However, the predominant problem in this type of composite material is the weak adhesion of the matrix-fiber interface, probably attributed to the nature of the surface and the hydrophobic character of the natural fibers, thus leading to weak mechanical properties for the material, envisaged composite. The purpose of this study is to treat palm fiber with a basic solution of sodium hydroxide (4% w/v NaOH) for varying periods of time: 3, 7, 24 and 48 hours to improve interfacial adhesion. The results obtained from the tests carried out on the composite reinforced with palm fibers treated during 7 hours, showed a clear increase as regards the resistance to bending and compression; it is respectively of the order of 57 and 60%, compared to the composite reinforced by the untreated fibers. It can be deduced that palm fibers can be considered as one of the suitable materials for clay reinforcement.

A Combined [Formula: see text]-Consecutive-[Formula: see text]-out-of-[Formula: see text] and Consecutive-[Formula: see text]-out-of-[Formula: see text]: F System consists of [Formula: see text] components ordered in a line such that the system fails iff there exist at least [Formula: see text] consecutive failed components, or at least [Formula: see text] nonoverlapping runs of [Formula: see text] consecutive failed components, where [Formula: see text]. This system was been introduced by Mohan et al. [P. Mohan, M. Agrawal and K. Sen, Combined [Formula: see text]-consecutive-[Formula: see text]-out-of-[Formula: see text]: F and consecutive-[Formula: see text]-out-of-[Formula: see text]: F systems, IEEE Trans. Reliab. 58 (2009) 328–337] where they propose an algorithm to evaluate system reliability by using the (GERT) technique, in the independent case. In this paper, we propose a new formula of the reliability of this system for nonhomogeneous Markov-dependent components. For a Combined [Formula: see text]-Consecutive-[Formula: see text]-out-of-[Formula: see text] and Consecutive-[Formula: see text]-out-of-[Formula: see text]: F System with nonhomogeneous Markov-dependent components, we derive closed-form formulas for the marginal reliability importance measure of a single component, and the joint reliability importance measure of two or more than two components using probability generating function (pgf) and conditional pgf methods.