Polymer Matrix Composite in High Voltage Applications: A Review

In recent years, natural fibers have become more widely used as reinforcement in polymer composites to generate low-cost products. Fibrous reinforcements in polymer matrices lead to good mechanical and electrical properties for composite materials. Depending on the grade and orientation, composites can be one-fifth the weight of steel while offering similar or better stiffness and strength. In addition, unlike steel or aluminum, composites do not rust or corrode. Composite materials reinforcing phase gives durability, strength, and stiffness. Composite materials have traditionally been employed as structural materials. Composite materials are increasingly being used in electrical applications such as bushings, circuit breakers, coupling capacitors, and so on, thanks to the growing growth of the electrical sector. The design parameters for structural and electrical composites differ dramatically due to the enormous differences in property requirements. Depending on the application, structural composites. Structural composites prioritize sufficient strength and modulus, while electrical composites prioritize superior dielectric constant, thermal conductivity and low thermal expansion, and shielding effectiveness. In the electrical industry, low density is desired because it allows for weight reduction. It is also desirable to have a high strength-weight ratio and dielectric properties. This paper provides a brief review of the properties of polymer composite materials and their application in the high voltage industry.

A Review of Sensing Technologies for Non-Destructive Evaluation of Structural Composite Materials

The growing demand and diversity in the application of industrial composites and the current inability of present non-destructive evaluation (NDE) methods to perform detailed inspection of these composites has motivated this comprehensive review of sensing technologies. NDE has the potential to be a versatile tool for maintaining composite structures deployed in hazardous and inaccessible areas, such as offshore wind farms and nuclear power plants. Therefore, the future composite solutions need to take into consideration the niche requirements of these high-value/critical applications. Composite materials are intrinsically complex due to their anisotropic and non-homogeneous characteristics. This presents a significant challenge for evaluation and the associated data analysis for NDEs. For example, the quality assurance, certification of composite structures, and early detection of the failure is complex due to the variability and tolerances involved in the composite manufacturing. Adapting existing NDE methods to detect and locate the defects at multiple length scales in the complex materials represents a significant challenge, resulting in a delayed and incorrect diagnosis of the structural health. This paper presents a comprehensive review of the NDE techniques, that includes a detailed discussion of their working principles, setup, advantages, limitations, and usage level for the structural composites. A comparison between these techniques is also presented, providing an insight into the future trends for composites’ prognostic and health management (PHM). Current research trends show the emergence of the non-contact-type NDE (including digital image correlation, infrared tomography, as well as disruptive frequency-modulated continuous wave techniques) for structural composites, and the reasons for their choice over the most popular contact-type (ultrasonic, acoustic, and piezoelectric testing) NDE methods is also discussed. The analysis of this new sensing modality for composites’ is presented within the context of the state-of-the-art and projected future requirements.

Evaluating the Multifunctional Performance of Structural Composites for Thermal Energy Storage

The simultaneous need for high specific mechanical properties and thermal energy storage (TES) function, present in several applications (e.g., electric vehicles), can be effectively addressed by multifunctional polymer-matrix composites containing a reinforcing agent and a phase change material (PCM). The PCMs generally decrease the mechanical properties of the host structural composites, but a multifunctional composite can still be beneficial in terms of mass saving, compared to two monofunctional units performing the structural and heat management functions individually. To quantify any possible advantages, this paper proposes an approach that determines the conditions for an effective mass saving at the system level and ranks the investigated structural TES composites with a parameter called multifunctional efficiency. It is found that the potential mass saving is higher when the volume fraction of the reinforcement is kept constant also when the PCM fraction increases or when the single phases (reinforcement, PCM) are themselves multifunctional.

High Frequency Electromagnetic Shielding by Biochar-Based Composites

We report on the microwave shielding efficiency of non-structural composites, where inclusions of biochar—a cost effective and eco-friendly material—are dispersed in matrices of interest for building construction. We directly measured the complex permittivity of raw materials and composites, in the frequency range 100 MHz–8 GHz. A proper permittivity mixing formula allows obtaining other combinations, to enlarge the case studies. From complex permittivity, finally, we calculated the shielding efficiency, showing that tailoring the content of biochar allows obtaining a desired value of electromagnetic shielding, potentially useful for different applications. This approach represents a quick preliminary evaluation tool to design composites with desired shielding properties starting from physical parameters.