Carbon Fiber Reinforced Polymer with Shredded Fibers: Quasi-Isotropic Material Properties and Antenna Performance

Abstract

A carbon fiber reinforced polymer (CFRP) laminate, with the top layer consisting of shredded fibers, is proposed and manufactured. The shredded fibers are aligned randomly on the surface to achieve a more isotropic conductivity, as is desired in antenna applications. Moreover, fiber shreds can be recycled from carbon fiber composites. Conductivity, permittivity, and permeability are obtained with the Nicolson-Ross-Weir method from material samples measured inside rectangular waveguides in the frequency range of 4 to 6 GHz. The decrease in material anisotropy results in negligible influence on antennas. This is shown by measuring the proposed CFRP as ground plane material for both a narrowband wire monopole antenna for 5.9 GHz and an ultrawideband conical monopole antenna for 1-10 GHz. For comparison, all measurements are repeated with a twill-weave CFRP.

Carbon Fiber Reinforced Polymer With Isotropic 60 GHZ Reflectivity

“…The variations in reflectivity of the plain-CFRP and shred-CFRP are 0.8 ± 0.6 dB and 0.6 ± 0.6 dB, respectively. The isotropic reflectivity of shred-CFRP is aligned with the isotropic conductivity at 6 GHz [14]. Reference measurements with aluminum show a variation in receive power of 0.6 ± 0.6 dB.…”

“…Those of twill-weave CFRP and shred-CFRP are found in [14]. In most practical applications isotropic materials, which have little influence on reflectivity and antenna patterns are preferred.…”

Simulation Model for Chassis Antenna Cavities Made from Carbon Fiber Reinforced Polymer

“…It is well known that the conductivity of unidirectional CFRP is heavily anisotropic [10], which has a large influence on antenna performance. On the contrary, we have previously carried out extensive measurements to quantify the influence of quasi-isotropic CFRP onto antennas [12], [27]- [29]. CFRP with woven and shredded fibers have a quasi-isotropic conductivity in the single digit gigahertz region, which only varies within one decade (10 4 -10 5 S/m) [12].…”

“…On the contrary, we have previously carried out extensive measurements to quantify the influence of quasi-isotropic CFRP onto antennas [12], [27]- [29]. CFRP with woven and shredded fibers have a quasi-isotropic conductivity in the single digit gigahertz region, which only varies within one decade (10 4 -10 5 S/m) [12]. Measurements with narrowband monopole antennas [27], wideband monopole antennas [28] and whole automotive shark-fin antenna modules [29] show, that woven and shredded CFRP act as quasiisotropic antenna ground planes with only negligible influence on radiation patterns.…”

“…The radio-frequency properties of CFRP generally depend on a variety of parameters such as fiber type, fiber volume fraction, ply weave and laminate buildup sequence. Although CFRP laminates are anisotropic in general [10], recent publications demonstrate that the production of CFRP laminates with quasi-isotropic electric conductivity is feasible [11], [12]. The use of these CFRP with quasi-isotropic conductivity then only results in small changes in antenna performance, which can be neglected in automotive applications.…”