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This article provides an in-depth exploration of the current state of research in microwave-absorbing composite materials, juxtaposing the status quo of coating type and structurally reinforced resin-based composites, with a particular emphasis on the latter's structural and performance superiority. It succinctly elucidates the mechanisms of electromagnetic shielding, as well as the conditions and underlying principles that govern the absorption of microwaves by composite materials. The review continues by dissecting the strategies for enhancing the microwave-absorption capabilities of resin-based composites, including the classification of absorbents, absorbent selection, and an overview of structural design innovations in microwave-absorbing materials. Structural wave-absorbing composites are manufactured by combining different types of resin matrices, absorbers, reinforcing fibers and construction methods. The interactions between these components are scrutinized to reveal how each contributes to the overall performance of the composite. We spotlight the unique construction methods and the intricate relationship between structure and performance in structurally reinforced composites, offering insights into the optimization strategies for composite-material absorption characteristics. Concluding with a forward-looking perspective, the article contemplates the burgeoning potential and future applications of fiber-reinforced resin-based microwave-absorbing composites, setting the stage for a new era in material science and technology. [ABSTRACT FROM AUTHOR]

In this work, Phthalonitrile containing benzoxazine (BA‐ph) and Bisphenol A based cyanate ester (CE) were chosen as the matrix resin. Various amount of nano‐SiO2 was incorporated into BA‐ph/CE and their glass fiber‐reinforced composite laminates were fabricated. Curing reaction and processability of BA‐ph/CE/SiO2 blends were studied by differential scanning calorimetry and dynamic rheological analysis. Results showed that BA‐ph and CE exhibited good processability and curing reaction of BA‐ph/CE was not obviously affected by SiO2. Scanning electron microscope images of the composites showed that SiO2 particles were well dispersed in BA‐ph/CE matrix. Moreover, SiO2 could act as physical crosslinking points and diluent in matrix as well as between the glass fibers to improve the mechanical properties of composite laminates. As the results of dynamic mechanical analysis and thermogravimetry analysis, composite laminates possessed satisfactory Tg and good thermal stability. With incorporation SiO2 particles into matrix resin, dielectric constant and dielectric loss of BA‐ph/CE/SiO2/GF composites were increased and showed frequency dependence. [ABSTRACT FROM AUTHOR]

ABSTRACT Phthalonitrile containing benzoxazine (BA-ph) and cyanate ester (CE) were chosen as the thermosetting matrix and the glass fiber (GF) reinforced laminates formed at low temperature were designed. The polyarylene ether nitriles containing pendent carboxyl groups (CPEN) was selected to modify the interfacial interaction between the resin matrix and GFs. Two methods of introducing CPEN were compared and the effects of CPEN on curing behaviors and properties of the composites were investigated. Results showed that with the CPEN, exothermic peaks shifted to lower temperature and curing temperatures of BA-ph/CE decreased slightly. The mechanical and thermal properties of GF-reinforced composites were discussed and the results indicated that the composites of modified GFs with CPEN exhibited outstanding mechanical properties, higher glass transition temperature ( Tg > 290 °C) than that of composites composed of CPEN mixed with BA-ph/CE. Moreover, GF-reinforced composites showed stable dielectric constants (3.8-4.5) and low dielectric loss (0.005-0.01), which were independent of the frequency. In sum, the various methods of the introduction of CPEN in the GF-reinforced composites may provide a new route to prepare improved composites, meanwhile, composites with outstanding processability and excellent mechanical and thermal properties are expected to be widely applied in the fields of high-performance structural materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45881. [ABSTRACT FROM AUTHOR]