An investigation on EMI shielding effectiveness of carbon/epoxy composites with introduction of discontinuous fillers

• Main Author: Lin, Fuxiang.
• Other Authors: Chen Zhong
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/15297
• Institution: Nanyang Technological University

Electromagnetic interference (EMI) shielding materials demand has been on the rise due more prevalent use of communications devices. Metals have been predominantly used as the material of choice for these shielding applications. Due to its weight limitations, metals are not suitable for used in manufacturing for highly portable devices. A search for light weight materials capable of providing EMI shielding is required and polymer composite based material is one such alternative that is widely used in the market. Addition of conductive fillers to electrically insulating polymer resins has been studied to improve EMI shielding property in polymer composite materials. Electrically conductive and magnetic fillers can be used in composites for shielding applications while providing light weight shielding materials. Shielding theory for composite materials, however, is largely undeveloped, unlike metals. Models developed for metals cannot be used to predict the shielding effectiveness behaviour provided by a composite containing a wide range of conductive fillers. The shielding effectiveness (SE) of three different discontinuous fillers added carbon-fiber filled epoxy-matrix based composites was studied over the frequency range (300 to 1000 MHz). The effects of incident electromagnetic wave (EM) frequency, filler conductive and magnetic properties, filler volume percent and filler particle size (radius) were examined. The objective of this analysis is to characterize the factors involved in determining the shielding effectiveness of a composite. From this analysis, a model that increases shielding effectiveness for carbon fiber filled epoxy-matrix based composites is developed. This study indicates that using highly conductive discontinuous fillers in carbon-fiber filled epoxy-matrix based composites would effectively increase its shielding effectiveness. With higher filler loadings and larger filler particle size, higher shielding effectiveness for carbon-fiber filled epoxy-matrix based composites can be achieved. The reason behind this increase in shielding effectiveness is resulted from using larger filler particles which allow good dispersion and connectivity of particles in the carbon-fiber filled epoxy-matrix based composites, thus increasing the overall shielding effectiveness.