Composite Materials and Structures

The growing concerns about the environment and energy have driven the widespread adoption of new lightweight materials such as polymer composites in many industrial sectors, crucial issues being performance, cost efficiency, and multifunctionality (Krawczak, 2019). Among them, thermosetting matrix composites offer not only many advantages such as high specific stiffness and strength and their consolidated use in primary aircraft structures but also technical issues such as long processing times, limited fracture toughness, reduction of mechanical properties in the presence of water and solvents, and difficulty of end-of-life treatment (Krawczak, 2011). A key cultural problem is associated with the need of a chemical reaction during part fabrication performed in mechanical/aerospace/naval industries.

Although the use of thermoplastic matrix composites in aeronautic structures has been proposed since the second half of the 80s (Nguyen and Ishida, 1987; Maffezzoli et al., 1989), their first application was at the beginning of the third millennium with the wing leading edge of Airbus A380 (Offringa, 2005). Their demand is continuously increasing (JEC Observer, 2020) since they offer many advantages such as high toughness, long storage time, easy repairing and recycling, higher performances in hot-wet conditions, and ability to be thermoformed and heat-welded. However, manufacturing issues such as high processing temperature, fiber impregnation, and warpage still need a deeper knowledge (Advani and Hsiao, 2012). Thermoplastic composites can play a key role in the 21st century industry as new materials are emerging day by day, as manufacturing processes are evolving to meet the severe industrial requirements of performance, production, and multifunctionality (Advani and Hsiao, 2012; Boisse, 2015), and as sophisticated numerical simulation tools are making virtual prototyping and engineering more reliable than ever (Binétruy et al., 2015; Boisse, 2015). In that field, innovation is multifaceted and may come either from the constitutive materials (high-performance engineering thermoplastic matrices, commingled semipreg of fibers/thermoplastics, self-healing, bio-based or biodegradable matrices, natural or thermoplastic fibers, 3D textile reinforcement…) or from the manufacturing processes (automated out-of-autoclave processes, hybridization/coupling of technologies, additive manufacturing, hybrid welding…). Moreover, thermoplastic composites allow for automated, high-speed mass production with reduced need for secondary operations (Mafeld, 2014), creating increased interest in the industry for various applications: aerospace and defense, automotive and rail transportation, construction and building, energy, oil and gas, sporting goods, drones, etc. Also, thermoplastic composites offer an interesting recycling potential using mechanical, thermal, or chemical processes (Oliveux et al., 2015). As thermoplastics, it is quite easy to recycle them by regrinding, compounding/blending, and reprocessing; additionally, they are at the forefront of current industrial scale-up attempts of chemical recycling, making it possible to recover not only fibers but also feedstock or original monomers which can eventually be re-polymerized to produce new polymers.
This Research Topic focuses on the latest advances and developments of fiber-reinforced thermoplastics, mainly referring to continuous fiber-reinforced composites and of related processing technologies. A collection of seven articles addresses some challenging issues related to advanced manufacturing processes, such as consolidation by compression molding (Ayadi et al.), injection-overmolding (Akkerman et al.), reactive pultrusion (Zoller et al.), joining by ultrasonic (Villegas) or induction (Scarselli et al.) welding, as well as solid-state drawing (Walker et al.) or electrospinning (Sessini et al.) of fibers. Numerical modeling and simulation, and performance assessment through advanced characterization techniques, correlating microstructure and properties, are also addressed. These papers highlight how thermoplastic matrix composites can be processed, adopting a completely different paradigm in comparison to thermosetting matrix ones, the former not requiring a reaction to set the properties but complex thermal cycles, often performed in a short time span.
The Guest Editorial team is confident that this collection of papers will benefit a large community in research and application of advanced thermoplastic composite materials so as to further advance along the pathway toward sustainability, performance, and competitiveness.

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing filament. The device design takes advantage of both the open source hardware methodology and the paradigm developed by the open source self-replicating rapid prototyper (RepRap) 3-D printer community. Specifically, this paper describes the design, fabrication and operation of a RepRapable Recyclebot, which refers to the Recyclebot's ability to provide the filament needed to largely replicate the parts for the Recyclebot on any type of RepRap 3-D printer. The device costs less than $700 in mate rials and can be fabricated in about 24 h. Filament is produced at 0.4 kg/h using 0.24 kWh/kg with a diameter ±4.6%. Thus, filament can be manufactured from commercial pellets for <22% of commercial filament costs. In addition, it can fabricate recycled waste plastic into filament for 2.5 cents/kg, which is <1000X commercial filament costs. The system can fabricate filament from polymers with extrusion temperatures <250 °C and is thus capable of manufacturing custom filament over a wide range of thermopolymers and composites for material science studies of new materials and recyclability studies, as well as research on novel applications of fused filament based 3-D printing.

This research work investigates graphite-epoxy design for light weight high performance structure of an aircraft wing spar using computational techniques. MATLAB MuPAD software was used to derive analytical models for the aircraft wing loads using symbolic computation to estimate shear and bending moment forces acting on the wings while ANSYS 14 Mechanical APDL software was used to design and analyze the modeled composite structures of the wing spar. To carry out progressive failure analyses of the various graphite-epoxy composite wing spar designs under bending moment, finite element analysis with ANSYS 14 Mechanical APDL software was employed to determine which spar design would best withstand the bending moment of 10,000Nm generated from the MATLAB MuPAD software. The investigation revealed that all the three designs of Low Modulus (LM) spar, High Modulus (HM) spar and Ultra Modulus (UM) spar failed at 16,801.8 N/m 2 which is above the wing bending moment with ultra-modulus spar having the least deflection of 0.143× 10 −3 m because of its high stiffness property.

Cleanrooms are the areas in which the many climatic parameters like Temperature, Relative humidity, Air velocity, Noise level, Odor, Dust particles, Oxygen level and Radiations are controlled and maintained within a required range. Out of all the above said parameters Dust particles and noise levels are considered in this study. Dust particles may enter the cleanroom from the outer un classified region or they may get generated by dust producing sites within the system itself. The dust generating sites may be the components within the cleanroom system start producing dust particles, may be because of wearing and tearing of the sliding surfacesor may be because of rust produced by oxidation of ferrous materials present over there in the cleanroom. The sound level is the next parameter which needs to be controlled within the cleanroom system. The sound may be from outside the system or may be because of the vibrating components present inside the system. The sound which enters from outside can be eliminated by sealing the area properly but the sound which is getting generated because of the moving and vibrating bodies needs to be controlled by proper design and selecting proper materials to produce them. In this study one components (Blower fan) which is present in the cleanroom system and has active involvement is taken into consideration. Blower fan is used in the cleanroom to circulated the air within the system and to maintain required pressure within the duct and cleanroom system. Normally blowers are manufactured by ferrous materials because of easy material availability and machinability and also by considering its low cost. But in this study Aluminum composite material reinforced with E-glass and carbon fibers has been considered to produce the blower fan. It has been considered because the material is light in weight,corrosive resistant,nonmagnetic, abundantly available,good aesthetic look,easy machinability and good thermal conductor. Because of its light weight rotating parts produce less vibration and less noise. Because of its corrosive resistance property, the rusting will not come into picture, if it is not there then the particle generation because of rusting will not come into picture. The only drawback of this material is, it is having low strength. But its strength can be improved with the help of some reinforcements like E-glass and carbon fibers.

Many standardised durability testing methods have been developed for Portland cement-based concretes, but require validation to determine whether they are also applicable to alkali-activated materials. To address this question, RILEM TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ carried out round robin testing of carbonation and chloride penetration test methods, applied to five different alkali-activated concretes based on fly ash, blast furnace slag or metakaolin. The methods appeared overall to demonstrate an intrinsic precision comparable to their precision when applied to conventional concretes. The ranking of test outcomes for pairs of concretes of similar binder chemistry was satisfactory, but rankings were not always reliable when comparing alkali-activated concretes based on different precursors. Accelerated carbonation testing gave similar results for fly ash-based and blast furnace slag-based alkali-activated concretes, whereas natural carbonation testing ...

Because of their mechanical properties and low density, flax fibers seem to be competitive with glass fibers. However, these fibers present a non-uniformity in many of their characteristics (non-constant diameter along the fiber, variable length, presence of defects). This leads to a dispersion of their mechanical properties. This study focuses on the development of fully biodegradable green composites based on poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) matrix reinforced by flax fibers to determine their elastic characteristics and to analyze their tensile and flexural failure in order to evaluate the influence of the processes on the mechanical properties. The main task is to incorporate flax fibers of several millimeters into the polymer matrix and study of the influence of the twin-screw extrusion and single-screw extrusion which are used for the elaboration of the compound and after the injection of the materials. The first objective is to identify the optimal parameters of the manufacturing processes which permit to elaborate satisfactory products presenting acceptable mechanical properties. The study aims to understand the effect of the introduction of flax reinforcements from a thermal and mechanical point of view. From the main results, the thermal analyses show that the introduction of 20% PBS into the PLA matrix improves the thermal stability of PLA and increases the onset temperature of decomposition. The mechanical characterizations have shown that the stiffness of the resulted composites has been improved after the incorporation of the flax fibers from 1457MPa to 4353MPa compared to the matrix. On the contrary, a decrease in deformation rate was observed owing the addition of flax fibers from 4.4% to 1.9%. These preliminary results show the possibility to develop new bio-composites which are thermoplastic, recyclable, with configurable mechanical properties depending on the selected matrix.

The role of transverse shear is crucial in modeling ultrasonic wave propagation in composites. The approximate plate theories have been extremely useful in providing solutions to problems involving static and dynamic loadings of uniform or laminated plates of finite dimensions. Moreover, since their simple formulations, they can also be useful for solving wave propagation problems in laminates of finite thickness and large lateral dimensions. A four-node plate bending element based on first order shear deformation theory is used in this work to predict the propagation velocity of first antisymmetric Lamb wave mode in graphite/epoxy composite plates by numerical simulation. Calculations are made using material properties obtained from a unidirectional panel via mechanical tests. For investigation, propagation along multiple directions is evaluated. Experimental and numerical results are compared at different angles of propagation and agreement between experimental and numerical approaches is found. © 2014 Elsevier Ltd.

This research work mainly focuses on stabilization of Ikpayongo laterite using cement blended with Rise Husk Ash (RHA) and Carbide Waste (CW) to promote its physical characteristics. The blending of cement with Rice Husk Ash (RHA) and carbide waste (CW) was done in proportion to determine the required proportion suitable for the stabilization of Ikpayongo laterite. Atterberg limit test, Compaction test, California Bearing Ratio (CBR) test, Specific Gravity, Unconfined Compressive Strength (UCS) test and Durability test were conducted on the laterite sample. The blend of cement with RHA and CW at interval of 0% to 10% displayed better results than the cement treated soil at some percentages. The result showed that at 2% and 10% cement content the MDD of the natural soil reduced from 2.015Mg/m3 to 1.917Mg/m3 and increased to 1.987Mg/m3 respectively, it also reduced to 1.870Mg/m3 when treated with 2% blend of 80% cement 10% RHA 10% CW and increased at 10% of the cement blend. The CBR v...

The high-performance composite materials based on carbon fiber are increasingly used in critical security areas (aeronautics, civil engineering). Thus, it is important to know their characteristics during curing process or their use. We present herein a technique of electrical impedance analysis to extract some specific material properties (resistance and capacitance) in order to know its behavior. As the material microstructure contains a conductor part (carbon fiber) and an insulator part (resin), a model of electrical conduction in the material was established by using a network of a resistance RP connected in parallel with a capacitance CP (impedance Z). Spectroscopic impedance analysis of the studied samples informs about the intrinsic properties of material and shows a sensitivity of these electrical parameters (RP, CP) according to the curing cycle. Then the sensitivity to some physical parameters (temperature, deformations, etc.) will be demonstrated in order to know the health of the material, thus ensure Structural Health Monitoring (SHM).

The effects of varying silicon carbide on the hardness values of heat-treated Al–Si–Fe/SiC particulate composites have been investigated. The 5–25% SiC additions were used for the production of different grades of Al–Si–Fe/SiC particulate composites. The composites samples were solution heat-treated at 500 °C for 3 h and quenched in warm water at 65 °C, aged at 100, 200 and 300 °C with various ageing time between 60 and 660 min at 60 min interval. Hardness measurements were made using Rockwell hardness tester. Experimental correlations obtained between the varying silicon carbide addition, heat-treatment parameters and the hardness values were analyzed using kinetic of ageing and factorial analysis (2K). The results show that hardness increases with increasing percentage of silicon carbide addition in the alloy and decreases with increasing ageing time. These results, which are in agreement with the experimental findings for these ageing time and temperatures. The increases in hardness values during ageing are attributed to formation of a coherent and uniform precipitation of the second phase in the matrix of the metal. A substantial improvement in hardness has been achieved in the reinforced metal matrices produced.

Synthetic fibers such as kevlar(aramid), glass, carbon etc. have been used for several years in many applications varying from aerospace components to civil infrastructures because of their added advantages such as light in weight, high specific stiffness, high specific strength, low density, good wear resistance. In this present work the effect of moisture on the mechanical properties like tensile strength and the failure behavior of kevlar fiber reinforced composite was investigated. Moisture was introduced into
the specimen by immersion in three different type of solution such as marine water, 30% conc. H2SO4 and 30% conc.NaOH at different intervals of exposure. The composite was made by bi-directional kevlar 49 fiber and epoxy resin by hand-lay-up technique. The result showed that the absorbed moisture decreases the tensile strength and breaking strength of kevlar fiber composite sample treated with marine water followed by NaOH and H2SO4.

The implementation of concrete and its association with a release agent influence the aesthetics of the concrete facings. The mineral oils tend to be replaced by vegetable formulations, to reduce the impact of the substances spilled in the environment. From a technical point of view, it is important to characterize the action of these new formulations at the interface concrete/oil/formwork. Two performing techniques have been used to study the physico-chemical processes, the tribometry and electrochemical impedance spectroscopy. The correlation of the results obtained allowed to improve the understanding of the mechanisms involved at the interface mould/oil, in connection with the use of an acidifier in the formulation. La mise en œuvre du béton et son association avec un agent de démoulage, influence l’esthétique des parements en béton. Les huiles minérales tendent à être remplacées par des formulations à base végétale, afin de réduire l’impact des substances rejetées dans l’environnement. Sur un plan technique, il est important de caractériser le mode d’action de ces nouvelles formulations, à l’interface béton/huile/coffrage. Les travaux s’appuient notamment sur l’utilisation de deux techniques performantes pour étudier les phénomènes physico-chimiques, la tribométrie et la spectroscopie d’impédance électrochimique. La corrélation entre les résultats obtenus permet d’améliorer la compréhension des mécanismes impliqués à l’interface de démoulage, en relation avec l’utilisation d’un acidifiant dans la formulation.

Within the framework of an experimental programme developed by the Laboratoire Central des Ponts et Chaussées (LCPC) and Électricité de France (EDF), in the aim of increasing knowledge on Alkali-Silica Reaction (ASR) and understanding the effect of water on ASR development in structures, two techniques have been designed to measure water content vs. time in large-scale concrete specimens. Global weighing variations are monitored on six 900 kg beams; and the, gammadensitometry measurement allows evaluating water content profiles in the beams. These two complementary measurements serve to validate water content models and correlate the moisture gradient with measured deformations The measurement principle, execution, and qualification are first described. The accuracy of the weighing device is thus evaluated at 10 g, and the uncertainty of the gammadensitometry method is close to 0.4% of relative mass. The paper then presents the results of one-year monitoring conducted on one of these beams and proves the consistency of these methods. At last, it is shown that the square root of time kinetics allows a good representation of the global mass variations of the beams and that the drying depth reaches between 80 and 100 mm after one year exposure. Dans le cadre d'une campagne d'expérimentation cofinancée par le LCPC (Laboratoire Central des Pont et Chaussées) et EDF (Électricité de France), destinée à approfondir les connaissances sur l'alcali-réaction et en particulier les conséquences de la teneur en eau libre sur le développment de cette pathologie dans des structures, deux techniques de suivi de l'évolution hydrique de ce type de corps d'épreuve de grandes dimensions ont été mises au point. La première permet de suivre la masse de six poutres d'environ 900 kg avec une précision de l'ordre de la dizaine de grammes. La seconde est une measure de gammadensimétrie, qui permet l'établissement d'un profil de séchage moyen avec une incertitude de 0,4% de masse relative. L'intérêt de cex deux mesures complémentaires est de pouvoir valider pa modélisation du gradient hydrique et de le relier aux déformations que en découlent. Après avoir exposé le principle, la réalisation et la qualification de ces deux méthodes de mesure, l'article présente près d'un an du suivi d'une de ces poutres. Il montre que l'évolution de sa masse respecte une loi en racine carrée du temps et que le front de séchage atteint une profondeur de 80 à 100 mm.

Sandwich structures are now extensively used everywhere due to their high strength and less weight. In this paper the impact tests on adhesively bonded sandwich beams are carried out. Sandwich beams with GFRP as a core material having aluminium facesheets are transversely impacted by a rigid projectile at various impact velocities of the projectile with the help of pneumatic gun. Various failure modes exhibited by the sandwich beams are encountered which involves large inelastic deformation, core shearing and delamination etc. I. INTRODUCTION At various occasions we come across impact phenomenon, fractures, and perforation in every field, whether it is a space vehicle or stone hitting by the mob, or any structural damage in a building or even a road accident. In engineering applications impact phenomenon has a wide meaning which describes energy absorption, resistance to damage etc. which had given rise to sandwich structures. Nowadays many applications are evolving prior to the use...

Course Description This course introduces students to the demands and conventions of academic reading and writing. It stresses on invention, drafting, revising, editing, and self-assessment, along with effective critiquing and collaborating. Students will be required to analyze texts as they build effective arguments in their writing. Instruction on the stages of the writing process, from prewriting exercises through rough drafts and revisions, forms a key part of the syllabus. The course stresses on the recursive nature of writing and reading-as well as their instruction-and is intended to offer students with a variety of forms of discourse leading towards exposition and argumentation in common Standard English. The course aims at continuing to develop students' practical fluency with sentence, paragraph and thesis-development skills but with increasingly complex applications. Rules and Requirements Students will be assigned a total of 32 pages of writing that will be divided among a number of short term essays (4 pages, typewritten and double-spaced pages). They will be required to revise at least three of these essays. There will be a short essay assigned at the beginning of the semester in order to assess a student's writing skills.

This research aimed to improving the quality of materials in order to produce composite board which had the standard score based on Indonesian National Standard (SNI). The focus of this research was the using of coconut shell powder as a filler material (filler), mixed with High Density Polyethlene (HDPE) recycling as a binder (matrix). On testing of the mechanical character obtained the varied nature i.e. for elastic strength was better on composition of the 60 : 40, elastic modulus was better on composition of the 50 : 50, internal adhesive strength was better on composition 30 : 70, impact strength was better on composition 70 : 30. In general, for the incorporation of the value of the mechanical composition of 50:50 indicated the dominant values to fulfill the Indonesian National Standard (SNI) 03-2105-2006. This research conducted a few tests which include mechanical testing on the samples that have been made. Mechanical tests including: Modulus of Rupture Test (MOR), Modulus of Elasticity (MOE), internal adhesion strength test and impact strength test.

This study was carried out on the mycoflora associated with seeds of different citrus species. Citrus seed material was collected from districts of Punjab, i.e. Multan, Sargodha and Khanpur. Standard methods were applied for the isolation and identification of fungi. A total of 11 fungi including Aspergillus fumigatus, Aspergillus flavus, Dreschslera tetramera, Alternaria alternata, Curvularia lunata, Macrophomina phaseolina, Aspergillus niger, Fusarium solani, Fusarium moniliforme, Rhizopus and Penicillium spp were isolated from the seeds of citrus. For control of isolated seed-born fungi, 3 recommended fungicides such as Ridomil Gold, Bavistin, Score and two chemical Salicylic acid and Boric acid, were used at 20, 30, 40 mg/10 mL and 5, 6, 7 µL/10 mL, respectively and chemical with 20, 30, 40 mg/10 mL. All these fungicide and chemicals significantly reuced with population of all fungi present in naturally infected seed samples. Ridomil Gold and Salicylic acid were found to be the best for the control of seed-born fungi of citrus seed at 40 mg/10 mL. The isolation and identification of different mycotoxins is essential to study health status of the citrus consumers and to safeguard the standards of WTO.

Abstract The aim of this study is to define an experimental model to predict acoustic absorption properties of porous asphalt concretes (PAC) as a function of composition and volumetric characteristics of mixes. The model can be used for the mix design of PAC and it enables to individuate which composition parameters to operate on in order to obtain optimum acoustic performances of low noise porous pavements. In order to define the experimental model, a large number of asphalt concrete samples, with high void content ...

The aim of the study is to investigate the tensile and flexural properties of carbon fiber reinforced polymer (CFRP) including graphene and styrene butadiene styrene (SBS). Experimental methods have been used in the study where several laboratory tests done on the carbon fiber reinforced polymer (CFRP) graphene and styrene butadiene styrene (SBS). The test specimen was cut according to ASTM standards. A universal testing machine (UTM) was used to investigate the tensile and flexural properties of carbon fiber reinforced polymer (CFRP). It was determined that styrene butadiene styrene (SBS) acts more correctly in increasing the stiffness of the CFRP's, whereas graphene is more powerful in achieving higher strength. Styrene butadiene styrene (SBS) added samples exhibited highest flexural and storage modulus among all types. Graphene delivered samples showed maximum improvement in tensile and flexural power and exhibited maximum strong tensile properties with highest power dissipation capability in tensile test. By contrast, addition of styrene butadiene styrene (SBS) reduced the stiffness and appreciably extended the stress to failure of the composites. The findings of the study show that primarily depends on the fiber orientation of carbon fiber reinforced polymer (CFRP).

—knitted fabrics find numerous applications in sportswear fabric industry, during their use it can be subjected to loading-unloading due to the body movements which can be indirectly affected by the dynamic elastic recovery value of the fabrics. The cyclic loads lead to the redistribution of fibers in the yarn structure, because they tend to get the minimum level of energy. Dimensional properties of knitted fabric are widely affected by the externally applied forces that could involve permanent deformation. Cotton/Spandex knitted fabrics are widely used for several applications. In this work, an attempt was done to analyze the effect of cyclic loading on cotton/spandex knitted fabric subjected to the different levels of cyclic loading under different values of initial extensions. Knitted fabric mechanical properties with different percentages of spandex were tested. The fabric properties and the number of cycles indicate the change of the residual extension and the drop in the fabric strength and stiffness.

Epoxy-based fiber–matrix composites based on a single-component curing system with pot times >>two weeks are described. Bisphenol-A-diglycidyl ether and hexahydrophthalic anhydride were used as epoxy matrix precursors; 1,3-dicyclohexyl-3,4,5,6-tetrahydropyrimi-dinium carboxylate (6Cy-CO 2) was used as latent pre-catalyst. Glass fiber-reinforced epoxy resins were obtained both via thermal curing under air and under vacuum-assisted resin infusion conditions. The high quality of the resulting composites and the absence of any air inclusion were confirmed by DSC and x-ray tomography. Rheological and kinetic data revealed that the 6Cy-CO 2-based systems allow for an advanced processing and outrival commercial amine-based hardeners in terms of speed of curing.

This project presents a study of lightweight Nomex honeycomb (BMS 15-5F) structure and woven glass fabrics reinforcement (prepreg –BMS 8-139) in terms of impact energy and Young Modulus properties. The lightweight structure is used to fabricate literature pocket for aircraft interior. A 5.1kgs weight impact load testing was performed on Nomex honeycomb structure with skin (10mm) and without skin specimens (specimen thickness is 8mm and 25.72mm) to determine the impact energy properties (ASTM D7136). Three point bending test was conducted on prepreg specimens with constant thickness of 1.44mm (ASTM D638) to determine Young Modulus. The result of the both tests are analysed and study. A simulation study also has been made using CATIA V5 software with 50 N loads. Thus, the best recommendation could be useful to improve the material for the literature pocket.

Kaolin and quartz from Pugu and feldspar from Morogoro were used to produce feldspathic dental porcelain bodies. Mineralogical results from XRD revealed the presence of kaolinite, illite, microcline and clinochlore in the kaolin samples; albite, microcline, sanidine in the feldspar samples and only silica in the quartz samples. The chemical results studies by XRF revealed the presence of in varying proportions. Particle size distribution of all the raw materials were determined and particles <63 μm were used for preparation of batches. The batches of different compositions with ranges: quartz (12-22%), feldspar (75-88%) and kaolin (3-5%) were fired at 1100, 1200 and 1250 o C, and the developed properties were tested. The physico-mechanical properties studied exhibited volumetric shrinkage between 2 and 55.17%, open porosity between 6.67 and 40.00%, water of absorption between 7.1 and 40%, bulk densty of 1.43 – 5.68 g/cm 3 , and compressive strength at 0.13-32.25 MPa. The optimal firing temperature for the best results was found to be 1250 o C. The results obtained indicate that kaolin and quartz from Pugu and feldspar from Morogoro are potential raw materials for the production of dental porcelain.

14 Numerous studies have shown that adding steel fibers to the concrete mixture improves both the shear 15 strength and ductility of reinforced concrete beams. Most current shear design formulations for steel 16 fiber reinforced concrete beams are empirically based and their predictions provide acceptable results 17 when compared with tests results, but only in limited ranges of the parameters involved. On the other 18 hand, many shear theoretical models suggested in the literature are derived by extending previous 19 formulations for conventional reinforced concrete beams, just introducing the stresses transferred across 20 the critical shear crack. Since the effects of steel fibers on the others shear resisting mechanisms are not 21 accounted for, “adjusting” empirical factors must be used to fit the experimental results. There is, 22 therefore, the need for developing mechanical models capable to rationally account for the effects of 23 steel fibers on the global shear strength a...

The paper provides an overview of tribological properties of nanocomposites with aluminium matrix. Nanocomposites represent a new generation of composite materials with better properties than conventional composite materials. The paper presents and explains the most common methods of nanocomposites production. In addition, the overview of tribological properties is presented through the equipment used for testing; amount, size and type of reinforcement; matrix material and manufacturing process; and test conditions. ARTICLE HISTORY Received 15 August 2016 Accepted 3 September 2016 Available online 30 September 2016

As a part of the framework of the development of ceramic products, scientific research continues this idea that clays are essential vehicles for local development in Africa; and therefore they deserve to be made profitable. This scientific work has the advantage of providing a solution to the housing of the Sahel area. On the other hand, this study can effectively serve as the basis of data in the formulation of ceramics from clay Maroua, in the region of the Far North Cameroon, for a large-scale industrial operation. Thus, two samples of materials respectively KO1 and IP2 have been the subject of a preliminary chemical and mineralogical size rheological study. Once formed, the tubes containing the KO1 and PI2 materials have undergone heat treatment at successive temperatures of 900˚C, 1000˚C and 1100˚C. The baked products obtained have also been the subject of a study of resonance, coloring density, loss on ignition, water absorption, linear shrinkage, porosity and mechanical compression.