Carbon fibers are fabricated from different materials such as special polyacrylonitrile (PAN) fibers, cellulose fibers and pitch. But PAN fibers are recognized as the most widely used precursor for the present-day manufacture of Carbon fibers. The process of fabrication Carbon fibers from special PAN fibers is composed of two steps including oxidative stabilization at low temperature and Carbonization at high temperatures in an inert atmosphere. Today Carbon fibers are still expensive because of the high price of their raw material (special PAN fibers).This study focuses on making Carbon fibers from commercial PAN fibers (low price PAN fibers used in textile industry). The results shows that in case of conducting complete stabilization process, it is possible to produce desirable Carbon fibers from commercial PAN fibers. With some changes in conventional procedure of stabilization in terms of temperature and time of operation, the desirable conditions of complete stabilization are achieved.

This work deals with the thermal, mechanical and dynamic properties of hybrid composites reinforced with Carbon fibers and aramid fibers, whose matrix is epoxy resin. In this study a series of hybrid fiber composite are prepared with Carbon and aramid fibers as reinforcement. Thermal properties are obtained by thermal gravimetric analysis (TGA), Thermo-mechanical analysis (TMA) and hot plate analysis. Also mechanical properties are obtained by tensile and modal analysis tests. The experimental results are compared with the similar theoretical ones. Besides the effect of stacking sequence and hybrid ratio (adding the number of layers of Carbon fibers), on the thermal and mechanical properties are investigated. The results show that by increasing the hybrid ratio although the weight of the sample is more, the thermal conductivity of the Carbon fibers used is higher than that of the aramid fibers and this increase in thermal conductivity causes the heat to be transferred to the sample much faster and the temperature of the glass increases with the increase of the hybrid ratio. Due to the high stiffness of Carbon fibers, adding it to the composite causes, the tensile modulus of the samples increases. By combining Carbon fibers with aramid fibers, the toughness of Carbon fibers can be increased and at the same time the brittle property of Carbon fibers is removed due to the malleability of aramid fibers. It is concluded that aramid fiber has an effective role in improving failure strain due to its high toughness and malleability, while Carbon fiber is very fragile. The lowest tensile strength occurs at the hybrid ratio of 29% with a value of 677. 66 MPa. which is very close to the theoretical critical hybrid ratio. The results also show when the Carbon fibers and aramid fibers are on the outer and the middle layers of the beam respectively, the frequency has a larger value because the aramid fibers have a very high impact resistance.

Elastomers and plastics are intrinsically insulating materials, but by addition of some conductive particles such as conductive Carbon black, Carbon fibers and metals, they can change to conductive form. Conductivity of these composites is due to formation of the lattices of conductive filler particles in polymer chains. In this report, conductivity of chloroprene rubber filled with Carbon black and Carbon fibers as a function of temperature and pressure are studied. Electrical conductivity of chloroprene in a function of temperature and pressure are studied. Electrical conductivity of chloroprene in the presence of Carbon black' with proper mixing conditions increases to the conductivity level of semiconductors and even in the presence of Carbon fibers it increases to the level of a conductor material Meanwhile, the sensitivity of this compound to heat and pressure rises. Thus these composites have found various applications in the manufacture of heat and pressure sensitive sensors.

Currently, Carbon quantum dots have attracted considerable attention due to their unique properties and desirable advantages. High crystallinity, water solubility, good dispersibility, small size, low toxicity, inexpensive raw materials, high chemical stability, environmental compatibility, low cost, stability under light, desirable charge transfer with advanced electronic conductivity, as well as specific thermal and mechanical properties are some of these features. Carbon quantum dots have various applications in different fields. Fabrication of precise chemical and biological sensors, bioimaging, solar cells, drug tracking, nanomedicine, light-emitting diodes (LEDs), and electrocatalysts are some of these applications. Biological sensors based on Carbon quantum dots are capable of detecting various metal ions, acids, proteins, biotin, polypeptides, DNA and miRNA, water pollutants, hematin, drugs, vitamins, and other chemicals. In the present study, the properties of Carbon quantum dots and some of their fabrication and applications methods have been addressed. In continuation of the paper, the effect of Carbon quantum dots on important factors in plants such as growth and development, photosynthesis, absorption and transportation of substances, resistance to biotic and abiotic stresses, as well as their application in agriculture has been investigated.

In this study, the distribution of residual stress in fiber-reinforced nanocomposites is investigated. Fiber-reinforced nanocomposite is composed of three substances: Carbon fiber, Carbon nanotube (CNT), and polymer matrix. Unit cells in hexagonal packing array with different arrays as unit cell, 3*3 and 5*5 arrays have been selected as suitable for finite element analysis of residual stresses. Radial and tangential residual stress have been determined in different directions by finite element analysis using ABAQUS commercial software for each phase individually. The effect of the CNTs’ various volume fractions (0%, 1%, 2%, and 3%) on residual stress distribution has been studied in different directions and compared to one another for each phase. Results show that the 3*3 unit cells arrays are suitable for modeling micro-residual stresses, and the results of this array are reliable. In addition, adding a 3% volume fraction of CNTs to the matrix is the best option for reduction of overall residual stresses with minimal fluctuation in local micro-residual stresses.

In this study, surface modification of silk fabrics was done through adsorbing multi-walled Carbon nanotubes (MWCNTs) on the silk fabric surface. For this purpose, a simple method of immersing silk in the solution MWCNTs dispersion was used. In order to increase adsorption of activated MWCNTs on the silk fabric surface, citric acid was used as a crosslinking agent in the presence of sodium Hypophosphite as a catalyst. Results of potentiometric measurements showed that electrical conductivity of CNT modified silk fabric increases with the concentration of CNTs in the solution. Washing fastness of the CNT modified samples were assessed by a spectrophotometer just before and after washing out. Brightness was increased for all samples after washing. Scanning electron microscope (SEM) images was used to investigate morphology of fabric surfaces. SEM images represent that, in the same density, accumulation of single-wall Carbon nanotubes was more in samples that obtained in presence of citric acid.

Dynamic and buckling of a composite beam reinforced with a combination of Carbon and aramid fibers is studied in this paper. The beam is under a thermal gradient through the thickness. Timoshenko beam is made of a polymer matrix (epoxy resin) reinforced with layers of high–strength Carbon and high-toughness aramid fibers in order to create a balance between stiffness and toughness and create a type of structural composite beam with excellent strength and toughness. The mechanical and thermal properties of the hybrid composite beams are obtained based on the mixed law method. The equations of motion are extracted based on the Hamilton principle and then solved by the generalized differential quadrature method (GDQ). In this study, a thermal gradient is applied to the beam and then the vibration and buckling response of this hybrid composite beam are studied. The main contribution of this paper is the vibration and buckling responses of a hybrid composite structure strengthened by Carbon and aramid fibers. The effect of the hybrid ratio as well as the stacking sequence on the free vibrations and critical buckling load are presented. The fundamental frequency and critical buckling load are largely affected by the stacking sequence. The conclusions show that the use of aramid fibers in the composite beam reinforced with Carbon fibers decreases the natural frequency as well as the critical buckling load of the beam. The conclusions also show that for the symmetric hybrid composite beam, despite the critical buckling temperature being the same, the critical buckling load is different and depends on the location of the fibers.

The fused deposition modeling (FDM) or material extrusion method is one of the most popular techniques for 3D printing. Given the challenges in producing 3D-printed parts with high mechanical strength and adequate surface quality, this study focuses on optimizing the parameters affecting the output fibers of a newly developed filament extruder, which has the capability of producing reinforced composite filaments. The optimization process involves evaluating parameters such as polymer melting temperature, filament collection speed, water bath temperature, and impregnation speed, and their effects on interfacial shear strength (IFSS). Statistical methods, such as design of experiments (DOE) and analysis of variance (ANOVA), were employed for this purpose. The results confirmed uniform impregnation of fibers and matrix through scanning electron microscope (SEM) images. It was also demonstrated that an increase in temperature does not necessarily lead to an increase in IFSS, and there is a risk of thermal degradation of the matrix. Moreover, low-viscosity melt can compromise geometric stability, indicating that temperatures above 230°C are not optimal for filament impregnation. Consequently, the optimal conditions for producing composite filaments with continuous Carbon fibers and polylactic acid (PLA) resin were determined to be a melting temperature of 190°C, water bath temperature of 50°C, filament collection speed of 2 rpm, and impregnation speed of 1 rpm.