Fabrication, Mechanical and Dielectric Characterization of 3D Orthogonal Woven Basalt Reinforced Thermoplastic Polyimide Composites
The 3D orthogonal woven basalt fiber reinforced polyimide (PI) composites were fabricated and characterized in this study. The PI film was firstly prepared to determine PI processing parameters. Fourier transform infrared (FTIR) analysis showed that 300°C was the suitable imidization temperature. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) results showed relatively good thermal properties of the PI film. In the fabrication of composites, the multi-step impregnation method was applied. The bending properties of 3 mm-thick composite showed increasing trend in all and the second-time impregnated composite had much higher value than the first-time impregnated composite. Moreover, the bending fracture mode photos showed obvious creases except for the first-time impregnated materials, which agreed well with the bending property values. The dielectric constants for the composites were complex because they had not regular value following the mixing rule of the composites, which was mainly due to the interfacial polarization and other effects in the fabrication processing.
Fabrication and characterization of structural/dielectric three-phase composite: Continuous basalt fiber reinforced epoxy resin modified with graphene nanoplates
Abstract A kind of multifunctional composite with combined dielectric and mechanical properties was prepared using conductive nanofiller to modify continuous fiber-reinforced polymer composite. The three-phase graphene nanoplates/basalt fiber/E-51 epoxy resin (GNPs/BF/E-51) composite was designed as structural/dielectric composite that could perform energy storage process and sustain mechanical loading simultaneously, possessing potential application as dielectric layer in structural capacitors. The effects of GNPs content on morphology, mechanical, dielectric and electrical properties of E-51 epoxy resin and BF/E-51 composite were investigated. Dielectric mechanism was proposed based on interfacial polarization and electron conduction process. Experimental results show that dielectric permittivity, dielectric loss and alternating-current conductivity sharply increase when GNPs loading reaches 1 wt% for GNPs/E-51 and 0.24 wt% for GNPs/BF/E-51, owing to different dispersing state of GNPs in composites. Mechanical properties of GNPs/BF/E-51 composite increase after the addition of GNPs. GNPs/BF/E-51 composite with suitable GNPs content demonstrates outstanding integrative dielectric and mechanical properties.
A micromechanical model for interpenetrating multiphase composites
Abstract The dependence relation between the macroscopic effective property and the microstructure of interpenetrating multiphase composites is investigated in this paper. The effective elastic moduli of such composites cannot be calculated from conventional micromechanics methods based on Eshelby’s tensor because an interpenetrating phase cannot be extracted as dispersed inclusions. Employing the concept of connectivity, a micromechanical cell model is presented for estimating the effective elastic moduli of composites reinforced with either dispersed inclusions or interpenetrating networks. The model includes the main features of stress transfer of interpenetrating microstructures. The Mori–Tanaka method and the iso-stress and iso-strain assumptions are adopted in an appropriate manner of combination, rendering the calculation of effective moduli quite easy and accurate.