Effect of Aramid Fibers on Balanced Mix Design of Asphalt Concrete

Fiber-reinforced asphalt concrete (FRAC) was tested using limestone, PG 64-22 binder, and 20% reclaimed asphalt pavement (RAP). After mixing fibers with different lengths and dosages, they were extracted and recovered to evaluate their dispersion in the FRAC. The uniaxial fatigue test, IDEAL CT test, and flow number test were performed on FRAC with different fiber lengths and asphalt contents. The balanced mix design (BMD) approach was then used to analyze the uniaxial and flow number test results in order to evaluate the effect of aramid fibers on fatigue and rutting resistance of the pavement. The dispersion test showed that the 19 mm and 10 mm aramid fibers at a dosage rate of 0.5 g/kg provided the best dispersion. The 19 mm fibers showed better performance test results than the 10 mm and 38 mm fibers. The BMD approach provided ranges of asphalt contents to produce mixes with certain resistances to fatigue and rutting. The BMD approach also demonstrated the effect of fibers with different lengths on increasing the resistance to fatigue and rutting. The study concluded that the 19 mm fibers with a dosage of 0.5 g/kg produce best results. The BMD approach is a good tool that can be used to refine the mix ingredients, including additives such as fibers, in order to optimize pavement resistance to various distresses such as fatigue cracking and rutting.

MATHEMATICAL AND PHYSICAL BASIS FOR DEVELOPING A SIMULATOR FOR TOWING AND PULLING OF WHEELED AND TRACKED MACHINES

The subject matter of the article is the towing and pulling of wheeled and tracked vehicles with the use of cable ropes and dynamic slings. The goal of the study is to determine the mathematical and physical basis for the development of a simulator for towing and pulling wheeled and tracked vehicles for researching to study the possibility of using aramid fibers of cable-ropes and dynamic slings. The tasks to be solved are: based on the analysis of the main roads and ground characteristics to formalize the list of calculated parameters and physical quantities determine the amount of evacuation work when pulling, towing and transporting wheeled and tracked vehicles; to develop a mathematical model that describes the process of pulling and towing wheeled and tracked vehicles using cable ropes and dynamic slings. General scientific and special methods of scientific knowledge are used. The following results are obtained. By analyzing the main characteristics of roads and ground, a formalized list of design parameters and physical quantities that determine the volume of evacuation work during the towing and pulling of wheeled and tracked vehicles was obtained. Mathematical model, describes the process of pulling and towing wheeled and tracked machines using cable ropes and dynamic slings have been compiled as a system of equations with different order. analyzed existing technology for the production of aramid fibers, their strengths and weaknesses, and formed a research polygon with regard to the peculiarities of the operation of wheeled and tracked vehicles. Existing technology for the production of aramid fibers, their strengths and weaknesses, and formed a research polygon with regard to the peculiarities of the operation of wheeled and tracked vehicles have been analyzed. Conclusions. The main roads and ground characteristics that determine the vehicles. evacuation conditions are the following: the type of road or ground, their possibility depending on the season and precipitation, the presence of ascents and descents, as well as the nature of road (ground) interaction with caterpillars determined by resistance coefficients. movement and traction. The mathematical model of pulling a wheeled and tracked vehicle using cable ropes and dynamic can be presented as a system of equations: the jerk carried out by the machine in time reflected third-order differential equation, assuming that all the energy accumulated by the cable is numerically equal to the work of moving stuck machine, corresponds to the equality of the corresponding integrals; the properties of aramid fibers that affect the strength and performance characteristics of cable ropes can be formally expressed through the elongation of the cable. Analysis of strength and service properties of aramid fibers opens the way to improvement of manufacturing technology of cable ropes and dynamic slings for pulling and towing of wheeled and tracked vehicles.

Reinforced Concrete Structures Containing Chopped Carbon Fibers with Polymer Composite Materials

In this paper, the reinforcement of concrete combining composite materials with carbon, glass and aramid fibers is discussed. Accordingly, cement specimens reinforced with chopped carbon fibers were manufactured via the retrofitting method and coated using various different types of fabrics (carbon, glass and aramid), and epoxy resin systems were developed and studied using compressive strength tests. In addition, polymeric matrix (epoxy resin) composite materials reinforced with different types of fabric (carbon, glass and aramid (Kevlar® 49)) were manufactured and their shear and bending strengths were measured. Before reinforcing cement specimens, all fabrics (carbon, glass and aramid (Kevlar® 49)) were placed in a vacuum chamber and were processed via pre-impregnation. This specific reinforcing method significantly improved the mechanical properties of cementitious structures with compressive strength values that reached 81 MPa. In a similar way, the bending and shear strengths of the materials under study were measured at 405 MPa and 33 MPa, respectively.

Testing the Force Absorption of Composite Materials to Select the Best for Making a Helmet

The paper presents and describes the procedure of testing the materials that were available for the production of a multifunctional protective helmet. The procedure was carried out at the company Šestan-Busch d.o.o. as part of the EU project for the development and production of a multifunctional protective helmet. The test results showed that carbon fibers polymers as a composite material have the best impact absorption properties which was a key criterion for material selection. Other materials; glass fibers polymers, aramid fibers polymers and combinations in the test procedure showed worse results compared to the selected criterion.

Development of Reinforcement Grout Materials Based on Blast Furnace Slag according to the Content of Reinforcement Fiber

The grouting is used to reinforce soft ground and to prevent the leakage of water in the soil. The objective of the study is to enhance the compressive strength of grout materials by using reinforcing fibers and to increase the strength of soil using blast furnace slag powder. For this purpose, cement was replaced with the blast furnace slag powder by 30 to 60%. Furthermore, for comparison of carbon fibers with aramid fibers, each fiber was added by 0, 0.5, and 1.0% of the weight of material. As the contents of carbon fibers and aramid fibers increased, the uniaxial compressive strength increased. This is due to the interlocking of fibers in the grout material that increased the uniaxial compressive strength. Moreover, the grout material reinforced with aramid fibers showed an increase of uniaxial compressive strength by at least 20% compared to the carbon fibers. An environmental assessment was done through a heavy metal leaching test and a pH test. The test result reveals that about 50% of chromium (VI) leaching decreased as 30% more blast furnace slag powder was used but the pH test shows about 0.5 pH increased as 30% more blast furnace slag powder was used. Further study is necessary for the pH test.

Property Assessment of High-Performance Concrete Containing Three Types of Fibers

This study investigated the mechanical properties and the effects of the volume fraction for carbon fibers (CF-VF), polypropylene fibers (PPF-VF) and aramid fibers (AF-VF) with a fixed aspect ratio of 650 for the carbon fibers, 400 for the polypropylene fibers and 900 for the aramid fibers in hybrid fiber-reinforced concrete (HFRC). Furthermore, compressive, splitting tensile and flexural tensile tests were carried out to obtain the optimal total volume fraction for the three types of fibers, as well as the optimal ratio between the CF-VF, PPF-VF and AF-VF. In addition, stress–strain curves of normal concrete and HFRC were examined to explore the whole mechanical process. The results indicated the CF-VF, PPF-VF and AF-VF have a significant effect on the tensile and flexural strengths of HFRC. The HFRC with a fiber additional ratio of 25:50:25 had the best hybrid effect. Moreover, a calculation method based on the compressive strength of normal concrete and HFRC and the volume fraction is proposed to calculate the strength of HFRC in engineering as a reference. Besides, a uniaxial compression constitutive mathematical model of normal concrete and HFRC is established.

One Surface Treatment, Multiple Possibilities: Broadening the Use-Potential of Para-Aramid Fibers with Mechanical Adhesion

Aramid fibers are high-strength and high-modulus technical fibers used in protective clothing, such as bulletproof vests and helmets, as well as in industrial applications, such as tires and brake pads. However, their full potential is not currently utilized due to adhesion problems to matrix materials. In this paper, we study how the introduction of mechanical adhesion between aramid fibers and matrix material the affects adhesion properties of the fiber in both thermoplastic and thermoset matrix. A microwave-induced surface modification method is used to create nanostructures to the fiber surface and a high throughput microbond method is used to determine changes in interfacial shear strength with an epoxy (EP) and a polypropylene (PP) matrix. Additionally, Fourier transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy were used to evaluate the surface morphology of the fibers and differences in failure mechanism at the fiber-matrix interface. We were able to increase interfacial shear strength (IFSS) by 82 and 358%, in EP and PP matrix, respectively, due to increased surface roughness and mechanical adhesion. Also, aging studies were conducted to confirm that no changes in the adhesion properties would occur over time.

Application of Aramid Nanofibers in Nanocomposites: A Brief Review

The diameter of fibers is a critical factor in determining their final applications. When the diameter of aramid fibers changes from microns to nanoscale, its range of applications will be greatly extended. In this short review, the preparation of aramid nanofibers (ANFs) with diameters from ten nanometers to more than one hundred nanometers is introduced. Due to their excellent mechanical properties and their chemical and thermal stability, ANFs have been widely used as novel nanomaterials and composited with other materials, mainly for use in reinforced composites, energy storage, filtration and adsorption, biomedicine and electromagnetic fields. In this short review, the application of ANFs and their composites during the last 10 years is concisely summarized and a brief perspective on ANFs and their composites is also presented.