In this article, the strength of the filament produced by the extrusion method has been investigated. For this purpose, testing samples were produced using ABS and carbon nanotubes as printable nanocomposite filaments in 3D printer. Carbon nanotubes were incorporated into ABS, and nanocomposite filaments were produced and their strengths were measured. In order to predict the strength of a nanocomposite filament, a suitable multi-scale model was developed. This model started from the microscale and after passing the in-between scale of meso, ended at the macroscale. For each scale, a suitable and separate representative volume element was defined, and its strength was predicted. Two parameters, CNT length and orientation, were captured at the microscale, and CNT agglomeration was taken into account at the mesoscale. Finally, at the macroscale, the strength of the nanocomposite filament was estimated using a genetic algorithm. In this study, the strength of the nanocomposite was calculated with two weight fractions of 0.1% and 0.5%, and it was observed that the final strength of the nanocomposite with weight fractions of 0.1% and 0.5% increased by 14% and 20%, respectively. The outputs of the modeling procedure were in very good agreement with experimental observations.

In this article, the strength of the filament produced by the extrusion method has been investigated. For this purpose, testing samples were produced using ABS and carbon nanotubes as printable nanocomposite filaments in 3D printer. Carbon nanotubes were incorporated into ABS, and nanocomposite filaments were produced and their strengths were measured. In order to predict the strength of a nanocomposite filament, a suitable multi-scale model was developed. This model started from the microscale and after passing the in-between scale of meso, ended at the macroscale. For each scale, a suitable and separate representative volume element was defined, and its strength was predicted. Two parameters, CNT length and orientation, were captured at the microscale, and CNT agglomeration was taken into account at the mesoscale. Finally, at the macroscale, the strength of the nanocomposite filament was estimated using a genetic algorithm. In this study, the strength of the nanocomposite was calculated with two weight fractions of 0.1% and 0.5%, and it was observed that the final strength of the nanocomposite with weight fractions of 0.1% and 0.5% increased by 14% and 20%, respectively. The outputs of the modeling procedure were in very good agreement with experimental observations.

The fused deposition modeling (FDM) is an emerging technology for producing parts with high flexibility in design. Considering the low strength of the parts produced with PLA filament, the use of composites reinforced with continuous carbon fibers can solve this defect and increase the mechanical characteristics of the above produced parts. Therefore, an attempt has been made to design and build a prototype of a filament machine with the ability to produce continuous fiber filament with the structure of polymer filament (PLA) and carbon fiber reinforcement. In order to optimally use the produced product (carbon filament-PLA), the experimental effect of the melting temperature of the polymer filament and also the filament collection speed on the surface shear resistance of the product produced by this device was investigated. In this research, factors such as fiber surface roughness, the degree of impregnation between fibers and matrix, the influence of the temperature of the impregnation unit, and the speed of filament exit from the machine have been investigated and evaluated. The results of investigations carried out by electron microscope images on the samples have confirmed the relative increase in fiber surface roughness in the fiber preparation stage using acetic acid and the high quality of carbon fiber impregnation by PLA melt. Also, by using Taguchi's experimental design, filaments were produced and then the produced samples were evaluated in the laboratory. By examining the experimental results, among the conditions considered by Taguchi method, the best melting temperature is 190 C˚ and the best collection speed is 1 rpm.

In this study the effects of enzymatic hydrolysis on drawn polyester filament yarns were investigated. Two multifilament yarns were drawn with different draw ratios at different temperatures and then they were hydrolyzed in similar conditions. The effects of hydrolysis were studied by means of measuring weight loss, moisture absorption, tenacity, elongation-at-break, IR spectrum and scanning electron microscope. Results of this research showed that the hydrolysis decreases the weight of polyester hanks by less than 0.5%. The strength loss due to hydrolysis reached a maximum of 10%, whereas the elongation-at-break of samples decreases by 7-25% due to hydrolysis. Hydrolysis also increased the moisture absorption of the polyester by up to 50%. The FTIR spectra as well as other results show that the effect of hydrolysis is limited to the surface of the substrate and hydrolysis is more affected by the increase in surface area rather than drawing.

The filament winding process is one of the most important and widely used processes in the manufacture of composite structures in order to achieve high strength and rigidity. In this process, there are important parameters such as fiber tension, how the fibers are twisted, the effect of layering, twisting angle, fiber twisting pattern of fibers, type of material suitable for twisting, etc., which can play a significant role in this the strength of the processstructure. In this regard, the twisting pattern has been less studied by researchers less than other parameters. In this research, the effect of fiber twisting pattern on the hydrostatic pressure threshold of epoxy glass cylinder has been investigated. For this purpose, first, glass/epoxy cylinders with 4 four different twisting patterns were made with ±,54 arrangement and subjected to hydrostatic test with internal pressures of 5-50 bar, where the amount of radial displacement in the middle of the cylinder was measured experimentally. In the following, the amount of radial displacement of cylinders due to the internal pressure was is also modeled using numerical analysis (Abaqus) and compared with experimental results. In order to validate the experimental and numerical results, theoretical model was used and the results were compared. All of the results obtained were in acceptable limits and showed that the twist pattern having with finer texture has a higher compressive strength. Also, the simulation results showed a good agreement with the experimental results.