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Copyright of Plastics Science & Technology / Suliao Ke-Ji is the property of Plastics Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Materials with lower dielectric loss and greater thermal and mechanical properties have drawn public attention with the rapid development of 5G technology. However, the mastery and understanding of the aging mechanism and working lifetime of these specific materials remain an open challenge. Here, we designed a glass fiber (GF)-reinforced acrylate–styrene–acrylonitrile/polycarbonate (ASA/GF/PC) composite and systematically investigated its aging behavior, aging mechanism, and lifetime prediction under long-term thermal and oxidative conditions. The aging behaviors regarding the mechanical, dielectric properties and color change were deeply analyzed at four aging temperatures. Results indicated that impact strength was applicable to estimate working lifetime. Assisted by general Arrhenius kinetic models, the predicted lifetimes were 22,334 days at 303 K, 8605 days at 313 K, 3517 days at 323 K, and 1516 days at 333 K, respectively. The study of aging mechanism confirmed that thermal degradation inevitably occurred in the ASA and PC phases, which provoked the appearance of newborn oxygen-containing groups and further induced the generation of cross-linked domains. The desired results provide a valuable reference to guide the widespread and long-term utilization of ASA/GF/PC composites in 5G technology. [ABSTRACT FROM AUTHOR]

Glass fiber‐reinforced polymer‐matrix (GFRP) composites are used to manufacture devices such as radomes, electrical insulators, and radar‐absorbing structures, many of which are used in applications with strict mechanical and dielectric property requirements. As such, designs and properties of GFRP composite materials should be regularly improved to guarantee their safe operation and meet their constantly evolving application requirements. In this study, glass fiber (GF) particles and epoxy resin 128 (EP‐128) were used to manufacture high‐performance EP/GF‐X composites with GF particle contents ranging from 5% to 40%. An investigation into their mechanical and dielectric properties revealed that EP/GF‐20 composite specimens presented the best mechanical performance with their bending strength and modulus reaching 159.68 MPa and 6521.92 MPa, respectively, and an average dielectric constant of 4.862 within the 10–105 Hz frequency range. A theoretical analysis of the EP/GF‐X composite specimens' dielectric constants using classic dielectric models based on the Lichtenecker, Bruggeman, Jaysundere‐Smith, and Maxwell‐Garnett rule‐of‐mixture equations indicated that the dielectric model based on the Bruggeman rule‐of‐mixture equation provided the dielectric constants closest to the measured values with a maximum deviation of less than −0.321% for EP/GF‐40 composites. This study provides a feasible strategy to control the mechanical and dielectric properties of GFRP composites. Highlights: Glass fiber (GF) particles and epoxy 128 (EP‐128) resin were used to manufacture high‐performance glass fiber‐reinforced epoxy (EP/GF‐X) composites.The composite manufacturing process was carefully controlled to ensure uniform distribution and orientation of GF particles in the EP‐128 resin.The mechanical and dielectric properties of the manufactured EP/GF‐X composites were effectively tailored by controlling the content and distribution of GF particles in the EP‐128 resin matrix.The dielectric constants of the EP/GF‐X composites were measured experimentally and predicted using various theoretical dielectric models.The Bruggeman model provided the dielectric constants of the EP/GF‐X composites closest to the measured values. [ABSTRACT FROM AUTHOR]

Dielectric composites with low dielectric constants (ε), low dielectric loss (tan δ), and excellent thermal-mechanical stability are highly desired for high signal transmission speed and high device integration. Polytetrafluoroethylene (PTFE) based composites exhibit tremendous potential due to the outstanding dielectric properties and high-frequency stability of PTFE. However, achieving PTFE-based dielectric composites with thermal-mechanical stability and low dielectric constant is challenging. Herein, we develop a glass fiber/polytetrafluoroethylene (GF/PTFE) composite for high-frequency communication applications with a designed skeleton structure. By the paper-making process, the glass fiber can be dispersed in random directions to set up a skeleton with the PTFE matrix entering the space in the fiber network. The modification of GF was also carried out to low down the dielectric loss of the composite. Benefiting from the supporting effect of the skeleton structure and surface modification, the thermal-mechanical stable dielectric composite was achieved with a low dielectric constant, and dielectric loss remained (m-GF content = 15 wt%, ε = 2.326 and tan δ = 5.24 × 10−3 at 30 GHz, xy-CTE = 29 ppm/°C and z-CTE = 47 ppm/°C). Moreover, the composites also have good dielectric constant frequency stability and thermal conductivity. Thus, this work provided an effective way to tailor the structure of functional composites with disordered fiber fillers. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Plastics Science & Technology / Suliao Ke-Ji is the property of Plastics Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, a new route for improving the absorbing performance of glass fibers (GFs) composites by introducing the reduced graphene oxide (RGO)/polypyrrole (PPy)/RGO coatings through the self‐assembly method and then the in‐situ polymerization method was proposed. The corresponding microstructure and electromagnetic parameters were measured by scanning electron microscopy, X‐ray photoelectron spectroscopy, and vector network analyzer. The result indicated that the RGO/PPy/RGO coatings can adjust the absorbing performance of GFs composites by its synergistic effect, thus exhibiting optimum impedance matching degree and high conduction loss ability. The minimum reflection loss value of the synthesized RGO/PPy/RGO/GFs composite can reach −55.8 dB with the thickness of 4.3 mm, and the effective absorption bandwidths (≤−10 dB) covered the entire X‐band. This work proved that the RGO/PPy/RGO coatings can be used to adjust the radar absorbing performance of GFs composites. [ABSTRACT FROM AUTHOR]

Rubber-based conductive composites are widely used in sensors, wearable electronic devices and electromagnetic fields. In this work, by using the two-roll milling and hot-pressing process, chopped glass fiber (CGF) and graphene (Gr) as additives, and acrtlinitrile-brtadiene rubber (NBR) as the matrix, a series of anisotropic flexible rubber-based composites were prepared. Using this preparation method, both CGF and Gr additives were directly arranged in the material. When the content of CGF was 1 wt.%, the tensile strength in both the T and W directions of the material reached 27 MPa and 28 MPa, respectively. When the content of CGF was fixed at 1 wt.% and Gr was 1.5 wt.% and the elongation at break in both directions reached 328% and 347%. By focusing on the comparison of the dielectric differences in the T and W directions in the X band, it was found that the directional arrangement of the additives led to differences in the dielectric properties. [ABSTRACT FROM AUTHOR]

Herein, the effects of multi-walled carbon nanotubes (CNTs) on the mechanical and dielectric performance of hybrid carbon nanotube-woven glass fiber (GF) reinforced epoxy laminated composited are investigated. CNTs are deposited on woven GF surface using an electrospray deposition method which is rarely reported in the past. The woven GF deposited with CNT and without deposited with CNT are used to produce epoxy laminated composites using a vacuum assisted resin transfer moulding. The tensile, flexural, dielectric constant and dielectric loss properties of the epoxy laminated composites were then characterized. The results confirm that the mechanical and dielectric properties of the woven glass fiber reinforced epoxy laminated composited increases with the addition of CNTs. Field emission scanning electron microscope is used to examine the post damage analysis for all tested specimens. Based on this finding, it can be prominently identified some new and significant information of interest to researchers and industrialists working on GF based products. [ABSTRACT FROM AUTHOR]

To expand the application of insulating glass fiber (GF) in the field of microwave absorption, one type of GF hybrids with carbon nanotubes (CNTs) and nickel (Ni) was successfully synthesized by chemical vapor deposition and electroless plating methods. By changing the reaction conditions, the morphology of GF hybrids including CNT's length, CNT's growth density, and Ni′s thickness could be adjusted. The as‐produced hybrids were used as multifunctional reinforcement to fabricate epoxy composites. The dielectric properties of composites were particularly measured from 1 to 18 GHz. It was found that the variation of GF hybrids structure significantly changed the dielectric properties of the composites in the tested frequency range. Furthermore, the analytical simulation work based on the experimental results was conducted for optimizing the structural parameters of multilayered composites. The results showed that the best reflection loss of −60 dB with a −10 dB range of 5.6 GHz could be obtained in an absorber with a triple‐layered structure composed by GF‐CNTs/epoxy with different CNT contents and GF‐CNTs@Ni/epoxy. Thus, the proposed hybrid method might be quite efficient for developing composites that can achieve high‐performance electromagnetic absorbing. [ABSTRACT FROM AUTHOR]

The alumina/hexagonal boron nitride/glass fibers cloth/Polytetrafluoroethylene (Al2O3–hBN/GFs/PTFE) composites were prepared by blending-impregnation followed by hot compression method, and the dielectric, thermal properties of the composites with various hBN fillers content (0–20 wt.%) were investigated. The results show that the thermal conductivity of the composites increase significantly, while the coefficient of thermal expansion (CTE) decrease gradually, with the hBN content increasing. Composite substrates with 20 wt.% hBN exhibited high thermal conductivity as 1.05 W m−1 K−1, which is 5.3 times that of pure PTFE. Such compositions may be a promising material in high thermal conductivity copper clad laminate. [ABSTRACT FROM AUTHOR]

In order to improve the thermal properties of polytetrafluoroethylene (PTFE) as a high-frequency microwave dielectric substrate, PTFE/glass fiber (GF) composites filled with Si3N4 were prepared by the method of combining cold pressing and normal pressure sintering. The effects of content of Si3N4 on microstructure, thermal and dielectric properties of the PTFE/GF composites were studied by scanning electron microscope, laser thermal conductivity analyzer, thermal dilatometer and impedance analyzer, respectively. The results showed that silane coupling agent (KH550) could improve the dispersibility of the Si3N4 particles in PTFE to some extent and Si3N4 fillers could significantly improve the thermal properties of PTFE. Compared with pure PTFE, the coefficient of thermal expansion of PTFE/GF composite filled with 45wt% Si3N4 decreased from 109 to 27 ppm/°C and the thermal conductivity increased nearly twice. The dielectric constant of PTFE/GF composites grew with the content of Si3N4 and had good frequency stability. Although the dielectric loss of the composites deteriorated with the addition of Si3N4, it was significantly decreased with increasing frequency, indicating that there is a potential application of Si3N4 filled PTFE/GF composites in the field of high-frequency dielectric substrate. [ABSTRACT FROM AUTHOR]

In recent years, dry‐type air‐core reactors have frequently experienced inter‐turn short circuits due to the aging of the inter‐turn insulation. In this paper, we prepared epoxy/glass fiber samples and carried out an accelerated thermal aging test up to 840 hours. In different stages of aging, we tested the surface insulation properties, dielectric properties, thermal and mechanical properties of the samples. The results show that: Flashover voltage drops significantly, and when aging for 35 days, it has dropped by 12.4%. This is because aging is accompanied by the conversion of shallow traps to deep traps and the reduction of conductive channels, which slows down the charge dissipation rate and decreases the flashover voltage. Dielectric, thermal, and mechanical properties also show a deteriorating trend. Through the analysis of the changes in thermal and mechanical properties, it is inferred that thermal aging will damage the epoxy matrix more than the glass fiber. In addition, combined with the scanning electron microscope, Fourier transform infrared spectrometer, and X‐ray photoelectron spectrometer characterization results, we believed that the main reason for the material deterioration is the detachment of the glass fiber and the break of the long chain of the matrix. This article has certain reference value for the subsequent engineering application and online monitoring of this material. [ABSTRACT FROM AUTHOR]

Silane coupled E‐glass fiber (SC‐EGF) and E‐glass fiber (EGF) reinforced bismaleimide (BMI)‐epoxy‐hydroxylated BaTiO3 (BTOH) nanocomposites with 1–5 wt% of BTOH nanofiller were fabricated by hand lay‐up method and compression molded. Surface hydroxylation of synthesized BaTiO3 nanoparticles was carried out using H2O2. Both BT and BTOH nanoparticles were characterized by SEM, XRD, and FTIR studies. Among the reinforced nanocomposites, SC‐EGF‐reinforced showed a remarkable increase in mechanical and dielectric properties. The tensile strength of BMI‐epoxy composite increased 1.56 and 3.10 times when loaded with 2 and 3 wt% of BTOH, respectively. Their flexural strength too increased 2.14 and 2.21 times upon 2 and 3 wt% of BTOH loading. BMI‐epoxy‐BTOH nanocomposites with 3 wt% of BTOH showed higher tensile strength, flexural strength, and dielectric strength indicating that it possesses better mechanical and insulating properties and composites with 2 wt% showed higher dielectric constant and lower dielectric loss indicating that this composition could be explored to high dielectric applications. [ABSTRACT FROM AUTHOR]

• The glass fiber filler is adopted as the filler. • The composition of the PVDF-glass fiber composites and the film formation are simple. • Within a specific content range, the BDS synchronously increase with the ε of the material. To make the product commercially viable and applicable, the inclusion of glass fiber filler with a low cost and medium dielectric constant (ε) is adopted as the filler. Synchronously, representative polyvinylidene fluoride (PVDF) with high permittivity and breakdown strength is selected as optimal polymer matrix. And surface modifying agent is employed as organic coatings to weaken the surface energy of glass fiber and boost the interfacial inter-action. An investigation of dielectric properties was conducted by preparing flexible composites consisting of various content of glass fiber. The ε of composites can be significantly enhanced in the PVDF composites with glass fiber, and the breakdown strength (BDS) is remained at a high level. Moreover, within a specific content range, glass fiber makes the ε and BDS of the material increase synchronously. This work provides a facile strategy for the development of excellent performance, simple preparation and low-cost flexible composites. [ABSTRACT FROM AUTHOR]

A glass fiber bulk yarn fabric with a graphite coating was produced, with the glass fiber bulk yarn fabric used as the base material, E44 epoxy resin as adhesive, low molecular 650 polyamide as curing agent and graphite, due to its low cost and low density, as the absorbing material. The influences of the graphite content, coating thickness and drying temperature on the dielectric constant and conductivity were the main focus of the investigation. The results showed that the glass fiber bulk yarn fabrics prepared with the graphite coating have good dielectric properties. In the frequency range used in the study, the content, drying temperature and coating thickness for the graphite coating were found to have a major influence on the real and imaginary parts of the dielectric constant, loss tangent value and the real and imaginary parts of the electrical conductivity. [ABSTRACT FROM AUTHOR]

In the current work, (Na x Li 1-x) 0.5 Nd 0.5 TiO 3 (abbreviated to NLNT100x, x = 0.3,0.4,0.5,0.6,0.7) ceramics were synthesized by solid phase reaction. X-ray diffraction analysis confirmed the successful synthesis of NLNT ceramics. Dielectric measurements of the synthesized ceramics show that the dielectric constant (ε r) is increased first as increasing x, then decreased at x > 0.5, meanwhile the temperature coefficient of dielectric constant (τ ε) varied toward negative direction with the increase of x. Then, composite substrates with high dielectric constants and adjustable τ ε were fabricated by filling polytetrafluoroethylene (PTFE) with 60 wt% NLNT100x ceramics and using 5 wt% E glass fibers (E-GF) as reinforcement materials. In order to improve the interfacial compatibility of ceramics with PTFE polymer, hydrogen peroxide (H 2 O 2) was used to enhance the hydroxyl group (-OH) on the surface of inert perovskite ceramics, which is conducive for ceramics to further react with silane coupling agent (F8261 in this work). The modified ceramic was homogeneously dispersed in PTFE and composites with excellent dielectric properties were obtained. When x is 0.6, the prepared NLNT/PTFE composite substrate has a dielectric constant (εr) of 10.4, a low dielectric loss (tan δ) of 0.0026, and a near-zero dielectric constant temperature coefficient (τε) of approximately −-0.9 ppm/°C. [ABSTRACT FROM AUTHOR]

In this work, three laminated Epoxy composites reinforced with five woven layers of E‐glass fabrics, jute fabrics and kenaf fabrics were characterized by broadband dielectric spectroscopy. The dielectric analysis was performed in temperature range from 20 to 180°C and frequency range from 0.1 Hz to 1 MHz. The Epoxy matrix shows the presence of four relaxation processes, which are attributed to the β relaxation process, α relaxation process, the quasi‐continuous conduction and the dc conduction. In the laminated composite reinforced with the E‐glass fabric, only one additional relaxation process was detected, which was attributed to the interfacial polarization effect known as Maxwell–Wagner–Sillar polarization. However, for the laminated composites reinforced with jute and kenaf fabrics, two additional relaxation processes were observed. While the first one was associated with the water dipoles polarization imputed to the presence of polar water molecules in jute and kenaf fabrics, the second was linked to the interfacial polarization effect. The latter phenomenon was investigated by an analytical study using the Havriliak‐Negami model. The best adhesion between reinforcement and Epoxy matrix was obtained with E‐glass fabrics. This study was supported by the thermal properties using a differential scanning calorimetry. POLYM. COMPOS., 40:2142–2153, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

An approach to enhance the dispersion state of graphene nanoplatelets (GNPs) has been proposed by the incorporation of nanodiamond (ND) particles. The ND particles act as nanoseparators between individual graphene sheets to suppress the van der Waals interactions among individual sheets as well as GNPs. Glass fiber/epoxy composites filled with equal amount of UV ozone treated GNPs and ND particles in 0.1, 0.3, and 0.5 wt% were manufactured by vacuum compression. The effect of hybrid nanofillers on the mechanical and dielectric properties of composites were evaluated by tensile and short beam shear testing and free space dielectric measurements. The results have shown an enhancement in the mechanical properties of glass fiber/epoxy composites at lower wt% of graphene with ND particles as dispersion enhancers. The inclusion of ND with GNPs did not enhance the dielectric properties of the composites due to their small surface area and lower conductivity. POLYM. COMPOS., 39:E2056–E2063, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Abstract A study on 0.8BaTi 4 O 9 -0.2BaZn 2 Ti 4 O 11 (BZT) filled and glassfiber (GF) reinforced polytetrafluoroethylene (PTFE) was described. The content of GF was 4 wt. %, and the BZT content varied from 26 wt. % to 66 wt. %. BZT complex phase powder was prepared by one synthetic route and modified using perfluorooctyltriethoxysilane (F8261). The microstructure, thermal properties, dielectric properties and temperature coefficient of dielectric constant of the composites were investigated in detail. The results revealed that BZT/GF/PTFE composites hold outstanding dielectric properties and stable thermal properties. Moreover, the specimens exhibited strong hydrophobicity due to the modification of filler using F8261. The BZT/GF filled PTFE composites exhibited reliable dielectric constant (ε r = 4.4), acceptable dielectric loss (tan δ = 0.001), low water absorption (0.02%) and a near-zero temperature coefficient of dielectric constant (τ ε = 1.57 ppm/°C) at filler with contents of 4 wt. % GF and 46 wt. % BZT. Highlights • 0.8BaTi 4 O 9 -0.2BaZn 2 Ti 4 O 11 ceramics were prepared by one synthetic process. • The surface of BZT was successfully modified by C 14 H 19 F 13 O 3 Si. • Modified BZT is hydrophobic resulting in low water absorption in composite. • Increasing BZT contents will increase the density and ε r of the composites. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Polytetrafluoroethylene (PTFE)/glass fiber (GF) composites modified by Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) was investigated. This study included the manufacturing process of PTFE/GF/FEP composites and the effects of the content of FEP on the properties of composites, such as porosity, dielectric properties ( $${{D}_{k}}$$ , $${{D}_{f}}$$ ), water absorption, temperature coefficient of dielectric constant ( $${{\tau }_{\varepsilon }}$$ ) and coefficient of thermal expansion (CTE). Furthermore, the miscibility of PTFE and FEP was also investigated. The compositions of the resin mixture are x wt% FEP + (100 − x) wt% PTFE (x = 0, 10, 20, 30, 40). The results show that as the content of FEP is 30 wt%, the composite has a minimum porosity, at the same time achieves optimum properties, including dielectric constant ( $${{D}_{k}}$$ ) of 2.2343, dielectric loss ( $${{D}_{f}}$$ ) of 1.4 × 10, water absorption of 0.019%, CTE of 29, 36 and 231 ppm/°C (X, Y, Z direction, respectively) and temperature coefficient of dielectric constant ( $${{\tau }_{\varepsilon }}$$ ) of −71 ppm/°C. It has been found that FEP addition results in improved performance of the composites than that of previous reported work. [ABSTRACT FROM AUTHOR]

The degradation of a thermally-aged bismaleimide-glass fiber composite system was assessed via spectroscopic methods. Composite samples were subjected to accelerated isothermal aging at temperatures (275, 300, 325, 350 and 375 ° C) near or above the suggested upper usage limit of 290 °C. Broadband dielectric spectroscopy was used to measure changes in the dielectric spectra of aged composites from 1 kHz to 2 MHz, while chemical changes in the resin were identified with Fourier transform infrared photoacoustic spectroscopy. Additionally, samples were mechanically assessed via a double-notch compression test. Relationships between the dielectric, photoacoustic, and mechanical properties were inferred from the results. [ABSTRACT FROM AUTHOR]

The curing behaviors and processability of 2,2-bis[4-(3,4-dicyanophenoxy)phenyl] propane (BAPh) and carboxyl-terminated butadiene acrylonitrile rubber (CTBN) were investigated using differential scanning calorimetry and dynamic rheological analysis. The results indicated that the introduction of CTBN significantly catalyzed the polymerization of the CTBN/BAPh system and that the processability of the CTBN/BAPh prepolymer could be controlled by temperature, processing time, and CTBN content. CTBN/BAPh/glass fiber (GF) composite laminates were prepared in this study. In terms of mechanical and dielectric properties, the CTBN/BAPh/GF composite laminate with 10 wt% CTBN content showed an outstanding flexural strength and modulus of 534 MPa and 32 GPa, respectively, as well as higher dielectric constant and lower dielectric loss compared with the BAPh/GF composite laminate. The results on thermal property showed that the CTBN/BAPh/GF composite laminate with 10 wt% CTBN could withstand a high decomposition temperature of 580°C under nitrogen and 520°C in air atmospheres. Hence, this work proposes an approach to improving the processability of phthalonitrile resin so as to further widen its industrial applications. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, glass fiber composite prepreg is manufactured with multi-walled carbon nanotube (MWNT) added epoxy using two different methods. Because MWNT agglomeration occurs, the calendering dispersion method is used to resolve this problem. The tensile and shear tests of glass/MWNT 1.8wt % added epoxy composite (CNT18) are conducted and the results are compared with the properties of a commercial glass/epoxy composite (GEP 118). The complex permittivity is measured using a network analyzer and a waveguide in the Ku-band. A single slab radar absorbing structure (RAS) is also designed and verified. It is found that the tensile and shear properties of CNT18 are sufficient to replace GEP 118 as a structural material. Furthermore, the-10 dB bandwidth and reflection loss of the RAS using CNT18 is 12.87 to 17.78 GHz (4.91 GHz) and-29.2 dB at 14.95 GHz, respectively. The measurement results align well with the simulation results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42019. [ABSTRACT FROM AUTHOR]

Novel glass fiber (GF)/bismaleimide composites with significantly improved flame retardancy, higher mechanical strength and lower dielectric loss were developed, of which the resin matrix is a new flame retarding resin system (BDDP) based on 4,4′-bismaleimidodiphenyl methane (BDM), 2,2′-diallyl bisphenol A (DBA) and [(6-oxido-6H-dibenz [ c , e ] [1,2] oxaphosphorin-6-yl)-methyl]-butanedioic acid (DDP). The influence of the loading of DDP in the matrix on the integrated performances of composites was intensively studied. Results show that GF/BDDP composites not only have significantly improved mechanical and dielectric properties, but also possess excellent flame retardancy. The main flame retarding mechanism of GF/BDDP composites is the condensed phase mechanism. The introduction of DDP significantly strengthens the interfacial adhesion between GF and the resin matrix, this is responsible for the attractive performances of GF/BDDP composites. [ABSTRACT FROM AUTHOR]

The treated hybrid fillers of aluminum nitride/glass fibers (AlN/GF) were performed to prepare the AlN/GF/epoxy composites by casting method. Results showed that the flexural and impact strength of the composites were increased firstly, but decreased with the excessive addition of AlN. The mechanical properties were optimal with 5 wt% treated AlN. The thermal conductivities of the composites were improved with the increasing content of AlN, and the thermal conductive coefficient λ was 1.412 W/mK with 70 wt% treated AlN, about seven times higher than that of pure epoxy resin. The dielectric constant and dielectric loss of the composites were increased with the increasing content of AlN. For a given AlN/GF hybrid fillers loading, the surface treatment of AlN/GF hybrid fillers exhibited a positive effect on the mechanical properties and thermal conductivities of the composites. POLYM. COMPOS., 35:381-385, 2014. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Abstract: The faces of low-observable radomes constructed with sandwich structures are usually made of glass fiber or aramid fiber composites due to their high specific strength and compatibility of stealth characteristics. In this work, a hybrid composite face composed of both E-glass/epoxy and aramid/epoxy composites for low-observable radomes was designed to exploit the better characteristics of both composites. Three design methods, including the characteristic medium thickness, the wavenumber and the dielectric wavelength methods, were applied to satisfy the functional requirements of composite faces. The three design methods were evaluated via three-dimensional (3-D) electromagnetic wave transmission analysis and the free space measurement method. [Copyright &y& Elsevier]

This study compares the mechanical, tribological, and dielectric properties of glass fiber-reinforced epoxy (GFRE), presenting various fiber/matrix adhesions. Three GFRE composites were studied. The only difference between them is in the initial preparation of fibers which is intentionally simplified compared to the complex sizings used in industry. Thus, fibers treated with aminosilane or silicone coupling agents were compared with fibers simply washed with deionized water.The dielectric measurements show the leading role of interfacial bonding in the trapping or diffusion of electric charges. To obtain high mechanical properties, a fiber treatment that contributes to the diffusion of electric charges along the fiber/matrix interface is preferred. In addition, after friction, a modification of the dielectric properties in all materials is observed, and the trapping or the diffusion of the charges along the interfaces can make it possible to lower the friction coefficient, or the wear. [ABSTRACT FROM AUTHOR]

Abstract: Electromagnetic wave reflections from glass fiber reinforced epoxy matrix composites with 0°/90° and ±45° fiber oriented plain-woven glass fabric (PW-GFRP-0/90, PW-GFRP-±45) at incident angles of 30°, 40° and 50° were measured in the frequency range 50–75GHz using a free-space reflection measurement system. The complex dielectric constants of both composites were calculated using a simple transmission line theory. The complex dielectric constants of PW-GFRP-0/90 and PW-GFRP-±45 are similar and were measured to be ε′=4.61±0.01 and ε″=0.16±0.002, respectively. The damage stored in PW-GFRP-0/90 and PW-GFRP-±45 was also evaluated by dielectric constant changes using the same system at an incident angle of 30°. For both composites, ε′ decreased with increasing applied stress and damage parameter. The dielectric constant change is effective for detecting the damage stored in composites and can be used to quantitatively evaluate the damage. [Copyright &y& Elsevier]

Abstract: Terahertz time domain spectroscopy in reflection configuration was assessed as a nondestructive evaluation technique for aircraft glass fiber composites. A technique for measuring the material properties of glass fiber composites using reflection geometry was demonstrated in addition to imaging of damaged glass fiber composites. Surface defects such as localized burn damage, puncture holes, and paint/composite removal were detected using amplitude and phase imaging methods. Hidden voids were also detected using the relative amplitude of the first Fabry–Perot reflection. The depths of discontinuities were then measured using a Fourier technique and then subtracting the incident pulse from the reflected pulse. Finally, nondestructive evaluation techniques for transmission and reflection configurations were compared. [Copyright &y& Elsevier]

The physical and mechanical (density, strength in tension and compression), thermophysical (CLTE) and dielectric (permittivity) properties of polymer composite materials based on fabric fillers made of mineral fibers with different chemical composition are investigated. It is shown that fillers with different chemical nature have a significant effect on the properties of polymer composite materials and determine their recommended applications. [ABSTRACT FROM AUTHOR]

Nanosized Fe2O3 doped methylsilicone resin/glass fiber composites have been successfully synthesized and the resulting composites were characterized by Fourier-transformed infrared (FT-IR), scanning electron microscopy (SEM) and spatially resolved energy-dispersive X-ray spectroscopy (EDS). The result of dielectric measurement shows that the doping of Fe2O3 nanoparticles is beneficial to the improvement of the dielectric properties of the methylsilicone resin/ glass fiber compositions. The elementary analysis of the composites at different temperatures was conducted, indicating that nanosized Fe2O3 is an excellent high-temperature decarbonizer for methylsilicone resin. [ABSTRACT FROM AUTHOR]

New high-performance polymer composites are desirable for various industrial applications. Two unsaturated polysilsesquioxanes (AcPhPOSSⅠ and AcPhPOSSⅡ) were designed and synthesized successfully, and their thermosetting resins (AcPhPOSS@GAP) and fiberglass-doped composites (AcPhPOSS@GAP@GF) were prepared by thermal curing of AcPhPOSS and glycidyl azide polymer (GAP). AcPhPOSS@GAP exhibited excellent transparency, especially AcPhPOSSⅡ@GAP with a transparency and haze of 84.0% and 3.0%, respectively. The heat and smoke release rates of AcPhPOSS@GAP@GF were about 69% and 50% lower, respectively, than those of AcPhPOSS@GAP. Further, the flexural strength and flexural modulus of AcPhPOSS@GAP@GF remained above 80 MPa and 11,000 MPa, respectively, after water treatment. This was due to the strong adhesion between the fiberglass and the matrix, which enabled them to effectively withstand the impact of adverse external conditions. AcPhPOSS@GAP@GF presented a low dielectric loss and high thermal conductivity, which prevented damage caused by heat accumulation. Thus, the prepared materials have excellent application prospects. [ABSTRACT FROM AUTHOR]

Abstract: Electromagnetic wave transmittances of plain woven fabric glass fiber reinforced epoxy matrix composite (PW-GFRP) and eight-harness-stain fabric glass fiber reinforced polyimide matrix composite (8H-GFRP) with 1.0mm thickness were measured in a terahertz (THz) frequency range. The transmittance values for both composites are nearly zero at a frequency of 1.0THz. The real parts of the complex dielectric constant, ε′(ω) are 4.45 and 3.87 for PW-GFRP and 8H-GFRP, respectively, in the frequency range from 0.2 to 1.0THz, and they are almost frequency independent. Conversely, the imaginary parts of the dielectric constant, ε′′(ω) for both composites linearly increases with increase of the frequency from 0.13 to 0.37 for PW-GFRP, and from 0.12 to 0.33 for 8H-GFRP. [Copyright &y& Elsevier]

For fiber reinforced composite laminates, properties of laminates can be significantly affected by interfacial properties. In this work, a kind of phthalonitrile containing aromatic ether nitrile linkage (PEN-BAPh) was applied to modify glass fibers (GFs). Cured PEN-BAPh on GFs surface were investigated by Fourier transform infrared spectroscopy (FT-IR) and Ultraviolet–visible spectroscopy (UV–Vis). Scanning electron microscope (SEM) and thermogravimetry (TGA) testing were also applied to confirm the modification. Then, modified fiber-reinforced phthalonitrile-based resin composite laminates were fabricated. As the results indicated that all of the composite laminates showed improved flexural strength, flexural modulus and glass transition temperature (T g = 296.8–299.6 °C). Improved interfacial adhesion was also studied via interlaminar shear strength (ILSS), impact strength test and monitoring the fracture surfaces. Stable dielectric constants, relative low dielectric loss and outstanding thermal stability (T 5% > 350 °C) were obtained for designed composite laminates. Image 1 • Phthalonitrile containing aromatic ether nitrile linkage (PEN-BAPh) was applied to modify glass fiber (GF) surface. • Copolymerization and molecular entanglement between PEN-BAPh and BA-ph/CE contributed to the interfacial adhesion. • Improved interfacial properties contributed to the increase of mechanical properties and T g (increased 16 °C). • Composites with improved interfacial properties were confirmed by flexural properties, DMA, SEM, ILSS and impact strength. • Decreasing of interfacial polarization and polar nitrile groups on GF surface leaded to improved dielectric properties. [ABSTRACT FROM AUTHOR]