Determining the elastic constants for composites with fibers is a continuous concern of researchers, being studied and analyzed Different types of materials, with Different topologies and geometries. In the work, these constants are determined for a composite reinforced with cylindrical fibers with a rectangular packing. The obtained results are applied for the calculation of these constants for a composite used in engineering applications.

This study investigated the effects of Different arrangements of three-dimensional fibers on polymer matrix composite thermal conductivity under heat flux boundary conditions. The thermal lattice Boltzmann based on the D3Q7 (three dimensions and seven temperature vectors) method is utilized to illustrate the thermal conductivity in 7 cases of PMC with a Different arrangement of 3D fibers. Nondimensional temperature fields, isothermals, nondimensional thermal conductivity coefficient, nondimensional mean, and local temperature in 7 cases of PMCs have been investigated. The non-dimensional thermal conductivity coefficient in each PMC has been analyzed to predict optimal levels of factors affecting this simulation to maximize and minimize the heat transfer rate. The results signified that nondimensional temperature field in a PMC with the arrangement of a fiber, triplet, and triangular perpendicular to heat flux had a greater rate than a PMC with the arrangement of fibers along the way heat flux. Also, the Maximum and minimum of nondimensional thermal conductivity coefficient were in PMC with the arrangement of triplet fibers perpendicular to heat flux, (𝑘𝑥, 𝑐 = 1. 017) and triangular fibers along the way heat flux, (𝑘𝑥, 𝑓 = 0. 809) respectively.

Slab on grade, also called floors on ground, are Different from other structural members. First, they are supported directly by soil, and their success or failure may depend more on the soil qualities than on the slab construction. Second, they carry equipment and floor finishes, and any defect in the slab's integrity or moisture resistance affects those elements. A floor slab undergoing drying shrinkage may not only crack, but also break the brittle ceramic tile it carries. Failure may also occur due to overloading. For reducing cracks propagation, control or contraction joints are used. In this research, 225 specimens by fifteen mix design with Different dosage of polypropylene and steel fibers were prepared for evaluating compressive, impact and flexural testing at the ages of 7 and 28 days. As a result, optimum dosage of polypropylene fibers was 1. 6 kg/m3 and at this dosage, impact resistance enhanced about 460% and flexural strength enhanced about 70% in comparison with control specimens. Steel fibers improved impact resistance and flexural strength about 312% and 58% respectively at the dosage of 30 kg/m3. Results also showed that compressive strengths of specimens are not significantly increased by using fibers.

In this research, a method for producing gum tragacanth (GT) fibers is presented. Ribbon type GT of Astragalus Gummifer species were obtained from local production lands. The gum was treated with alkali to increase its process ability, and allowed to stand for a period of time to reach the proper viscosity and/or to “ripen”. Samples with Different ripening times were prepared and their viscosities were measured to determine the effect of ageing time on viscosity. They were injected into a coagulation bath. Calcium chloride with Different concentrations was applied as the coagulant agent. The consolidated samples were washed under Different pH conditions. Finally, the mechanical properties of the fibers were measured and their scanning electron micrographs were taken. The results show that chemically modified GT can be processed into fibers with Different qualities.

Concrete, as one of the most widely used building materials, has brittle behavior. Concrete pavement design factor is the 28-day concrete flexural strength. Adding fibers to concrete is effective on the ductility behavior, impact resistance, energy absorption, crack resistance, abrasion resistance, and tensile strength of the concrete and prevents crack expansion. For this purpose, a laboratory research was conducted to investigate the effect of Different combinations of macro-synthetic fibers on the flexural strength of fiber-reinforced concrete, including flexural strength, average residual strength and flexural toughness. In this study, concrete specimens were constructed according to ASTM C1609, ASTM C1399 and ASTM C79 standards and were evaluated with four Different macro-synthetic polymer fibers. Results of the experiments showed that adding fibers to concrete joints, the flexural strength increased by 3. 31-16. 96 percent. Also, the flexural toughness and average residual strength increased by addition of the fibers. Meanwhile, due to the soft break of regular concrete, flexural toughness and average residual strength could not be computed.