Electromagnetic (EM) wave absorbing materials play an increasingly important role in modern society for their multi‐functional in military stealth and incoming 5G smart era. Dielectric loss EM wave absorbers and underlying loss mechanism investigation are of great significance to unveil EM wave attenuation behaviors of materials and guide novel dielectric loss materials design. However, current researches focus more on materials synthesis rather than in‐depth mechanism study. Herein, comprehensive views toward dielectric loss mechanisms including interfacial polarization, dipolar polarization, conductive loss, and defect‐induced polarization are provided. Particularly, some misunderstandings and ambiguous concepts for each mechanism are highlighted. Besides, in‐depth dielectric loss study and novel dielectric loss mechanisms are emphasized. Moreover, new dielectric loss mechanism regulation strategies instead of regular components compositing are summarized to provide inspiring thoughts toward simple and effective EM wave attenuation behavior modulation.

Dielectric Loss Mechanism in Electromagnetic Wave Absorbing Materials

The Babool, Sheesham, Mango, and Mahogany trees are commonly found in India. The wood-plastic composites (WPCs) were prepared by injection molding using wood dust of the selected Indian trees as the reinforcements in the polypropylene matrix. The mechanical, wear, and morphological characterizations of WPCs were performed. Different wood dust proportions were utilized to observe the comparative variation in Young's modulus, wear rate, and morphology of the WPCs. The resistance to natural weathering and biodegradability of WPCs were evaluated following ASTM D1435–99 and ASTM D5338-11 respectively. The degradation of the WPCs due to Ultraviolet-B (UVB) radiation is also examined. The structure-property relation was established and the usability of different WPCs for different applications was highlighted.

Experimental study on mechanical behavior, biodegradability, and resistance to natural weathering and ultraviolet radiation of wood-plastic composites

This Spotlight on Applications highlights the significant impact of microwave-assisted methods for synthesis and modification of carbon materials with enhanced properties for electrodes in energy storage applications (supercapacitors and batteries). For the past few years, microwave irradiation has been increasingly used for the synthesis of carbon materials with different morphologies using various precursors. Microwave processing exhibits numerous advantages, such as short processing times, high yield, expanded reaction conditions, high reproducibility, and high purity of products. On this frontier research area, we have discussed microwave-assisted synthesis, defect creation, simultaneous reduction and exfoliation, and heteroatom doping in carbon materials. By careful manipulation of microwave irradiation parameters, the method becomes a powerful and efficient tool to generate different morphologies in carbon-based materials. Other important outcomes are the flexible control over the degree of reduction and exfoliation of graphene derivatives, the generation of defects in graphene-based materials by metals, the intercalation of metal oxides into graphene derivatives, and heteroatom doping of graphene materials. The Spotlight on Applications aims to provide a condensed overview of the current progress in carbon-based electrodes synthesized by microwave, pointing out outstanding challenges and offering a few suggestions to trigger more research endeavors in this important field.

Microwave as a Tool for Synthesis of Carbon-Based Electrodes for Energy Storage.

In recent times, demand for light weight and high strength materials fabricated from natural fibres has increased tremendously. The use of natural fibres has rapidly increased due to their high availability, low density, and renewable capability over synthetic fibre. Natural leaf fibres are easy to extract from the plant (retting process is easy), which offers high stiffness, less energy consumption, less health risk, environment friendly, and better insulation property than the synthetic fibre-based composite. Natural leaf fibre composites have low machining wear with low cost and excellent performance in engineering applications, and hence established as superior reinforcing materials compared to other plant fibres. In this review, the physical and mechanical properties of different natural leaf fibre-based composites are addressed. The influences of fibre loading and fibre length on mechanical properties are discussed for different matrices-based composite materials. The surface modifications of natural fibre also play a crucial role in improving physical and mechanical properties regarding composite materials due to improved fibre/matrix adhesion. Additionally, the present review also deals with the effect of silane-treated leaf fibre-reinforced thermoset composite, which play an important role in enhancing the mechanical and physical properties of the composites.

https://www.mdpi.com/2073-4360/13/9/1369/pdf

Physical and Mechanical Properties of Natural Leaf Fiber-Reinforced Epoxy Polyester Composites.

This research focuses on the mechanical behavior of cost-effective novel hybrid fiber metal laminates (FMLs) based on aluminum (Al) 1050 alloy and jute/glass fiber reinforced epoxy composites. The ...

Fabrication of Cost Effective Fiber Metal Laminates Based on Jute and Glass Fabrics for Enhanced Mechanical Properties

Microwave absorbing properties of carbon fiber based materials: A review and prospective

Experimental and numerical study on mechanical behavior and resistance to natural weathering of sugarcane leave reinforced polymer composite

Abstract In the present work, a diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin was modified with the help of a liquid rubber (LR) obtained from the pyrolysis of rubber. Tensile tests on samples of rubber modified epoxy resins (REs) containing varying rubber volume fractions (RVF) were conducted to obtain their tensile properties. Fractographic analysis of fractured samples using field emission scanning electron microscopy (FESEM) revealed the presence of phase separated rubber zones characterized by microvoids, distributed uniformly in the epoxy domain. Young’s modulus and yield strength of REs were observed to drop with RVF. A three-dimensional (3D) finite element model was employed to predict the elastic properties and stress distributions in REs. Various stress distributions and their dependence on the properties of rubber were examined in detail through the model. The effect of rubber properties on bulk elastic properties of the REs were also studied. Lastly, the effective stress-strain relationship was predicted with the help of an elastic-plastic analysis. Predicted results showed coherence with experimental results.

Morphology and micromechanics of liquid rubber toughened epoxies

The use of natural fiber composites in the fatigue prone structures is limited due to the lower strength and durability when compared to the carbon fiber reinforced polymer composites. The present work focuses on improving the bending cyclic fatigue strength (CFS) of the sugarcane fiber reinforced epoxy composite (SFRPC) by a novel treatment method. The treatment has increased up to 40% fatigue life of SFRPC by fiber and interface strengthening. The fatigue life was evaluated using the standard bending cyclic fatigue test. The SFRPCs were prepared using a specially designed compression molding setup by the hand layup method. The sugar cane fibers (SCF) were treated using the waste glass powder and PVA adhesive. The statistical analysis was conducted to observe the effect of the treatment method, the load ration (R) on CFS of treated/untreated SFRPC. A comparison of CFS of SFRPC (treated/untreated) with CFRPC is presented based on the author's previous work. A finite element based model was constituted for predicting the elastic properties of SFRPC (treated/untreated) at different fiber proportions. Additionally, a finite element (FE) model was constituted using the transient analysis in ANSYS (Explicit Dynamics Module) for obtaining the deformation and Von Mises stress at different R for the corresponding life of the treated/untreated SFRPC sample. A theoretical explanation for improved fatigue behavior of SFRPC was presented using scanning electron microscopy (SEM) micrographs and FE results collectively. The stress-strain-life relations for treated/untreated SFRPC were established. It was found that the shear yielding resulted due to the fracture of the outer glass layer of the SCF resulted in the higher CFS of the treated SERPC.

Modeling improved fatigue behavior of sugarcane fiber reinforced epoxy composite using novel treatment method

Sheet metal brackets are used extensively in industries and other applications for fixturing and clamping purposes. Holes are commonly drilled in the brackets for weight saving purpose. The size and location of these holes is left to the designer’s prerogative. Which when done manually requires a lot of computational time and the results obtained are still not guaranteed to be globally optimal. In this paper, topological optimisation capabilities of a commercially available finite-element solver ANSYS 8.0 have been employed through APDL (ANSYS Parametric Design Language) to find the optimal layout of material in the brackets. Four common bracket configurations have been selected. The brackets are modelled in ANSYS assuming that there is a plane state of stress in each bracket. The modelled bracket is then meshed with the help of PLANE82 elements. The loads and boundary conditions are applied as per given. They are topologically optimized by the ANSYS supported Optimality Criterion methods and their optimal shapes (optimal material distribution) for given loads and boundary conditions are determined.

Dheeraj Gunwant

Papers

Microwave absorbing properties of carbon fiber based materials: A review and prospective

Experimental and numerical study on mechanical behavior and resistance to natural weathering of sugarcane leave reinforced polymer composite

Morphology and micromechanics of liquid rubber toughened epoxies

Modeling improved fatigue behavior of sugarcane fiber reinforced epoxy composite using novel treatment method

Topology Optimization of Sheet Metal Brackets Using ANSYS