Experimental study on axial compression buckling of glass fiber reinforced plastics solid pole with circular cross-section

Glass fiber reinforced plastics are widely used in civil engineering because of their advantages such as light weight, high strength, good pollution resistance, and corrosion resistance. This study investigated the buckling bearing capacity, failure characteristics, and slenderness ratios of GFRP solid bars with circular cross-sections subjected to axial compression. A total of 18 specimens were categorized into six groups. The slenderness ratios ranged from 57 to 123. It was found from experiments that the instability mode of the specimens was extreme point instability, and a bearing capacity platform phenomenon was observed when overall lateral instability occurred. The failure mode was axial and transverse tearing failure of the material in the middle of the specimen. During buckling, the tensile side was transformed from the compression of the resin matrix to tension in the fibers. The elastic modulus of glass fiber was much lower than that of the resin matrix. After tension occurred, increased deformation led to a rapid increase in lateral bending, which resulted in the phenomenon of the bearing platform. At ultimate deformation, brittle failure of the specimen occurred. The buckling load of the specimen decreased sharply with an increase in the slenderness ratio, and stress ratios decreased from 34.95% to 6.73%. It is suggested that the slenderness ratio not exceed 80. Finally, based on experimental results, a practical method for calculating the stable bearing capacity of solid GFRP poles is proposed.

Structural phase transition and negative thermal expansion in Cu1.8Zn0.2V2–x P x O7 solid solutions

Negative thermal expansion (NTE) is exhibited over the entire x range for Cu1.8Zn0.2V2–xPxO7. In particular, dilatometric measurements using epoxy resin matrix composites containing the spray-dried powder demonstrated that the thermal expansion suppressive capability was almost unchanged for x≤0.1. With increasing x, the x-ray diffraction peak position moves systematically, but some peaks are extremely broad and/or asymmetric, suggesting disorder in the internal structure. The crystallographic analysis confirmed NTE enhancement by microstructural effects at least for x=0.2. Preliminary measurements suggest higher resistivity and lower dielectric constant than that of pure vanadate, which is suitable for application to electronic devices.

Welding and Riveting Hybrid Bonding of 6061 Al and Carbon Fiber Reinforced Composites

Welding and riveting hybrid bonding technology was applied to join 6061 aluminum alloy and carbon fiber reinforced plastics (CFRP). The laser-arc hybrid welding process and stepped rivets were used in the experiments to reduce the impact of the poor heat resistance of composites. The effect of hybrid welding arc current on the formation and mechanical properties of 6061 Al/CFRP joints was studied. Tensile shear load up to 4.65 kN was achieved by adjusting process parameters. The welding process and mode of the fracture were analyzed. The hybrid bonded joint obtained consisted of two parts: a welded joint of Al plate and Al rivet, and a bonded interface between Al plate and CFRP plate. The mechanical properties of the hybrid joint were mainly determined by the Al plate/Al rivet welded joint. The results of the study show that there are three interfacial bonding mechanisms between aluminum and CFRP. In addition to mechanical bonding between the Al plate and CFRP plate, there were also metallurgical bonding of Al-Mg intermetallic compounds with resin matrix and chemical reactions of aluminum with resin and carbon fibers at the interface, which could improve the mechanical properties of the joints.

The effect of lamina configuration and compaction pressure on mechanical properties of laminated gigantochloa apus composites

This study aims to investigate the mechanical properties of bamboo apus (gigantochloa apus) as a natural reinforced composite material. Bamboo’s laminates of gigantochloa apus were used as reinforcement on the epoxy resin matrix. The parameters examined in this study are the configuration of lamina and compaction pressure. Laminate configuration varies in the number, thickness and direction of the lamina. Compaction pressures of 1.5 MPa, 2 MPa, and 2.5 MPa were used to fabricate the Laminated Bamboo Composites (LBCs). The stem of bamboo with a length of 400 mm was split to obtain bamboo lamina with a size of 400×20 mm. The thickness of bamboo lamina is varied between 1 mm, 1.5 mm, and 2 mm. The bamboo lamina is then preserved by watering it with a preservative solution in the form of 2.5 % sodium tetraborate solution and dried in an oven until the water content reaches 10 %. LBCs were made with a hand lay-up method. After the LBCs were molded, they were pressed with 3 variations of dies compaction 1.5 MPa, 2 MPa and 2.5 MPa. The tensile and bending tests were carried out on the LBCs. Tensile testing is performed in accordance with ASTM standard D3039 and the bending tests were conducted based on ASTM standard D7264. The results show that at each compaction pressure, the highest tensile and bending strength was achieved by LBCs with a thickness of 1 mm of bamboo lamina and 7 layers of bamboo laminates. The LBC with thinner bamboo lamina reinforcement and more layers has the highest tensile strength and bending strength, even it has a lower mass fraction. The LBCs with laminates oriented 0° exhibited greater tensile and bending strengths than the LBCs with laminates structured –45°/+45° and 0°/90°. The LBCs with the 0° laminates direction is matrix fracture followed by lamina fracture. In the 0°/90° direction, matrix fracture is followed by delamination in the 90° and 0° laminates direction. Delamination and lamina clefting were observed in LBCs with laminates oriented +45°/–45°.

Microwave Absorption Properties of Fe40Co60 Based Nanocomposites

Microwave absorbing materials are applied in stealth, communications and information processing technologies. This kind of material dissipates an electromagnetic wave by converting it into thermal energy. The nanostructuration of materials became a reliable route over the years to enhance the dielectric and magnetic properties, which induce the required interaction. Nanostructured Fe-Co alloys are soft magnetic materials that make them promising candidates for microwave absorption when combined with other materials. The aim of our study was therefore to investigate the microwave absorption properties of based nanocomposites. The nanocomposites were obtained by the solution dispersion method. Nanocrystalline alloys elaborated by mechanical alloying (MA) in a high-energy planetary ball mill (RETSCH PM400) were dispersed into commercial epoxy resin matrix to form thin polymer nanocomposites. The grain size refinement and structural properties changes during milling process were characterized using powder’s X-ray Diffraction (XPERT PRO MPD diffractometer) at different milling durations. XRD spectra analysis show that a grain size refinement of 4.54 nm was reached after 60h milling accompanied with 1.2 % microdeformations. Obtained powders were shaped in small discs for which resonant cavity measurements were undertaken. The based nanocomposites have been subject to an experiment of two-port S parameters measurement in a rectangular waveguide (R120). The microwave experiments involved a Network Analyzer (VNA). Obtained results in terms of reflection losses show a good absorbing characteristic over the [8-15] GHz microwaves band.

Egg shell powder extraction and its application for water hyacinth (Eichhornia crassipes) natural fibre polymer composite mechanical, thermal behaviour and characterization analysis: Aquatic waste into sustainable product

The goal of this study is to investigate the morphological and mechanical characteristics of water hyacinth plant fibre polymer composites using the aquatic waste of water hyacinth plant fibre as a reinforcement material. Our main objective has been to make successive sustainable products for commercial and household use using aquatic waste plants. As a filler material, the eggshell powder is used here, which is derived naturally. The composite sample's mechanical properties are increased by this process. A novel way of extracting fibre from hyacinth is used in this study by fabricating a mechanical fibre extraction machine of our own design. The main aim of this work is to convert the biological waste of water hyacinth plants into successful commercial products. Using compression moulding techniques, fibre reinforced polymer composites are produced from water hyacinth plant extracts. ASTM standards are followed for the evaluation of manufactured samples, mechanical tests, and absorption tests. Utilizing TGA analysis, it is possible to identify the maximum withstand and degrading temperatures of composite samples. In order to determine whether FTIR can reveal chemical functional groups and percentage crystallinity, XRD is used as well. The scanning electron microscope is used to locate fibre clusters and brittle fractures in composite samples. With the help of an epoxy resin matrix, the fibres from water hyacinth can be used to make particleboard and other lightweight materials. By the end of this study, it should be able to demonstrate that water hyacinth plant fibres are suitable for use as reinforcement for an epoxy resin matrix.

The Effects of Processing Parameters on the Wedge Peel Strength of CF/PEEK Laminates Manufactured Using a Laser Tape Placement Process

Manufacturing thermoplastic composites (TPC) with excellent mechanical properties requires advanced methods with reduced costs and better overall efficiencies. In this study, fiber-reinforced thermoplastic polymer composite laminates were manufactured using an automated fiber placement (AFP) manufacturing technology. The effects of processing temperature (from 320 ℃ to 500 ℃), lay-up speed (from 20 mm/s to 260 mm/s), consolidation force (from 100 N to 600 N), and prepreg tape tension (from 0 N to 9 N) on the quality of the resulting laminates manufactured using the laser AFP system were investigated. The interlayer bond strength was characterized using wedge peel tests on samples prepared with different process parameters. The studies were complemented by measurements of the thermal properties of the composites using different scanning calorimetry. The optimized process parameter windows were determined to be 360 ℃ to 400 ℃ for the irradiation temperature, 140 mm/s to 160 mm/s for the lay-up speed, 100 N for the consolidation force, and 3 N to 5 N for the prepreg tape tension, respectively. The microscopic analysis of the cross-sections and peel-damaged surfaces revealed that the different distributions of the resin matrix resulting from the different processing parameters affected the interlayer strength. These results may provide an important reference for manufacturing TPC used in aerospace, defense, and automotive applications.

UJI KONDUKTIVITAS TERMAL KOMPOSIT POLIESTER FILLER SERBUK KAYU ULIN (EUSIDEROXYLON ZWAGERI)

To find out the best thermal conductivity value on the volume fraction of ironwood polyester filler composite (Eusideroxylon Zwageri) and to determine the effect of the number of voids on the value of the thermal conductivity of the ironwood polyester composite composite (Eusideroxylon Zwageri). This study uses an experimental method by conducting thermal and microstructure conductivity tests to see the many voids that have formed. The object in this study uses ironwood powder. Data analysis techniques in this study used descriptive data analysis which is describing research results graphically in a table. Input parameters in analyzing data include variations in the mixture of ironwood powder and resin (20% -80%, 25%: 75% and 30%: 70%), and 100% resin. The results of the study of the effect of the volume fraction of ironwood polyester composite composites on the value of thermal conductivity decreased with increasing volume of ironwood powder with the smallest thermal conductivity value at 30% volume fraction of ironwood powder : 70% polyester resin matrix that is 0.041 W/moC. The influence of the amount of voids on the thermal conductivity value of ironwood polyester composite composites can be seen that the more voids the smaller the thermal conductivity values. The number of voids along with the increasing volume of ironwood powder.

Flame Retardancy and Mechanical Properties of Chitosan and DOPO with Different Mass Ratios in Epoxy Resin

This work focused on the effects of chitosan (CS) and 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide (DOPO) on the flammable propertied of epoxy resin matrix. The EP composites were fabricated by direct mixing method through a general curing method. The influence of CS, DOPO and CS / DOPO on the resin was investigated through cone calorimetry tests (CC), UL-94 vertical burning, limiting oxygen index (LOI), thermal gravimetric analyzer (TGA), differential scanning calorimeter (DSC) and thermogravimetric analyzer-Fourier infrared combined system (TG-FTIR). The char residues of modified EPs after CC tests were investigated by FTIR, EDX and XPS. Under the 10% addition of CS / DOPO in EP, with the mass ratio of CS and DOPO of 1 : 1, 1 : 2, 1 : 3, 2 : 1 and 3 : 1, the flame retardancy properties of EPs all increased, but only if EP/10% CS1/DOPO2 and EP/10% CS2/DOPO1 achieved a V-0 rating and their values of LOI were 33.7% and 32.5%, respectively. Compared with EP, the peak heat release rate, peak smoke produce rate and total heat release of EP/10% CS1/DOPO2 and EP/10% CS2/DOPO1 decreased, especially, total smoke release decreased by 61.9% and 71.0%, the char residuals amount increased by 84.3% and 41.6%, and the average CO2 yield decreased by 55.4% and 55.0%, respectively. It is worth nothing that the mechanical properties increased, especially the flexural strength increased by 36.0% and 38.4%, respectively. The results indicated that DOPO and CS had important synergistic effects for simultaneous increase both the flame retardancy and mechanical properties of EP composites.