The Effect of Manufacture Process on Mechanical Properties and Burning Behavior of Epoxy-Based Hybrid Composites

The production of hybrid layered composites allows comprehensive modification of their properties and adaptation to the final expectations. Different methods, such as hand lay-up, vacuum bagging, and resin infusion were applied to manufacture the hybrid composites. In turn, fabrics used for manufacturing composites were made of glass (G), aramid (A), carbon (C), basalt (B), and flax (F) fibers. Flexural, puncture impact behavior, and cone calorimetry tests were applied to establish the effect of the manufacturing method and the fabrics layout on the mechanical and fire behavior of epoxy-based laminates. The lowest flammability and smoke emission were noted for composites made by vacuum bagging (approximately 40% lower values of total smoke release compared with composites made by the hand lay-up method). It was demonstrated that multi-layer hybrid composites made by vacuum bagging might enhance the fire safety levels and simultaneously maintain high mechanical properties designed for, e.g., the railway and automotive industries.

Fatigue life predictions of carbon fiber reinforced plastic in specimens of double-shear bolted joint

It is noted that in modern aircraft composite structures there is a significant number of composite and metal-composite shear bolted joints, the fatigue life of which is an important factor to ensure the operating safety of such constructions. Thus, special attention is given to the evaluation of the layered composites fatigue life in such joints during tests and calculations of the similar structures components. Despite a considerable number of publications and studies on this subject, it can be observed that many important methodological issues have not been solved yet in this field. These problems can deal with the choice of the main mode of layered composites fatigue damage in shear bolted joints; the uncertainty of the basic fatigue curve; the practical absence of some models, representing diagrams of constant life fatigue for the layered composites in the joints under consideration; the uncertainty of fatigue damage summation rule in the layered composites in the investigated joints. Based on the review results and the data analysis of domestic and foreign publications including the results of specially conducted studies, the solutions to these problems are proposed. The proposed solutions were verified by analyzing the calculated and experimental data on the fatigue life of carbon fiber reinforced plastic laminates НТА7/6376 [45/-45/0/90]3S in the double-shear bolted joints specimens.

Carbon Nitride is a Non-Metallic Catalyst for Oxygen Electrodes for Fuel Cells

A thermo chemical method for the synthesis of layered composites of graphite-like carbon nitride from urea and melamine has been developed. The production of graphite-like carbon nitride has been proven, SEM, X-ray diffraction, Raman spectroscopy and elemental analysis. Electrochemical studies have established that the obtained composites are promising materials as metal-free catalysts for oxygen electrodes for fuel cells.

Interfacial structure and mechanical properties of the Ta/Re layered composites prepared by chemical vapor deposition

A novel Ta/Re layered composite with high temperature resistance, low cost, light weight, and excellent mechanical properties has been prepared by chemical vapor deposition, for improving the comprehensive service performance of the aerospace engine nozzle materials. The interface structure, element distribution, and mechanical properties of the Ta/Re layered composites have been studied with scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and tensile testing machine. The results show that the structure of the Ta/Re layered composites is flat and smooth, uniform, and dense. Further, the interface joint is a serrated meshing structure, which tremendously improves the interface bonding properties. The high temperature (1600 °C) tensile strength of the heat-treated Ta/Vol. 30% Re layered composite is 125 MPa, which is 2.8 times and 56.3% higher than the commonly used nozzle materials C103 and Nb521, respectively, whereas the raw material cost is only about 46% of that of pure rhenium. The heat treatment process enhances the mutual diffusion behavior of the atoms in the interface diffusion layer, and increases the thickness of the diffusion layer, besides changing the mechanical properties of the material. When the heat treatment process is at 1800 °C × 1 h, the highest tensile strength at room temperature is 739.61 MPa, which is 42.76% higher than that in a deposited state. This work can provide a reference for the further research of the Ta/Re layered composites.

Hierarchical Interfaces as Fracture Propagation Traps in Natural Layered Composites

Compared with their monolithic version, layered structures are known to be beneficial in the design of materials, especially ceramics, providing enhanced fracture toughness, mechanical strength, and overall reliability. This was proposed in recent decades and extensively studied in the engineering literature. The source of the property enhancement is the ability of layered structures to deflect and often arrest propagating cracks along internal interfaces between layers. Similar crack-stopping abilities are found in nature for a broad range of fibrillary layered biological structures. Such abilities are largely governed by complex architectural design solutions and geometries, which all appear to involve the presence of various types of internal interfaces at different structural levels. The simultaneous occurrence at several scales of different types of interfaces, designated here as hierarchical interfaces, within judiciously designed layered composite materials, is a powerful approach that constrains cracks to bifurcate and stop. This is concisely described here using selected biological examples, potentially serving as inspiration for alternative designs of engineering composites.

Investigation of Mechanical Behavior of Layered Metal-Rubber Composites Based on Steel and Aluminum Alloy

Metal-polymer composites are advanced materials for the aerospace, automotive and railway industry where details and elements of construction are affected by impact, cyclic and vibration loads. In the present work layered composites based on steel, aluminum alloy and rubber as intermediate layers were obtained by cold and hot bonding using adhesives. Adhesive lap-shear bond strength of layered composites fabricated by various techniques was determined using tensile shear test. To evaluate the mechanical behavior of layered metal-rubber composites under simulated operational conditions static, dynamic and cyclic, three points bending tests were carried out. The results of mechanical tests of these composites indicated that hot bonding is the most preferred fabrication method for the formation of increased mechanical characteristics.

Mechanical Properties of Hybrid Structures Incorporating Nano-Silica and Basalt Fiber Pellets

Recently, developing a nonferrous reinforcement system (corrosion-free system) using durable and ductile cement-based materials that incorporate discrete fibers has been a promising option for exposed concrete structures in cold regions or marine environments. Therefore, in this study, properties of a novel type of cementitious composite comprising nano-silica and a high dosage of slag were investigated. The hybrid (layered) composites assessed in this study were composed of two layers of different types of cementitious composites. Normal concrete (NC) was used in the top layer combined with a layer of fiber-reinforced cementitious composite (FRCC) reinforced with either the recently developed basalt fiber (BF) pellets (basalt fiber strands encapsulated by a polymeric resin or steel fibers (SF)) that were used at different dosages. The post-cracking behavior in terms of residual strength, residual index, and toughness are presented and discussed. The analysis of results showed the effectiveness of the BF pellets in enhancing the post-cracking behavior of specimens, as they behaved comparably to counterpart specimens comprising SF, which makes them a good candidate for infrastructural applications including rehabilitation such as new bridge girders or overlays.