Natural fiber and aluminum sheet hybrid composites for high electromagnetic interference shielding performance

Electromagnetic radiation has filled the world today. Unfortunately, this has led to vulnerability in electromagnetic interference, unwanted radiation that affects the normal operation of electronic equipment. Electromagnetic pollution has resulted in signal interference to electronic gadgets and could even damage their normal operation. In a bid to curtail this pollution, many methods have been developed to prevent these unwanted radiations from being emitted by sources or from being received by susceptible electronics.

Electromagnetic interference shielding occurs through reflection, absorption and multiple reflections of the radiation. The use of metal sheets and coatings, which operate primarily by reflection, is the most popular electromagnetic interference shielding method. Gold, copper, aluminum, and silver metal sheets with good reflection properties are normally used, but insufficient mechanical attributes and corrosion resistance limit their application.

Embedding a metal layer in a durable, corrosion resistance polymer matrix is a novel approach for overcoming the typical drawbacks of metal sheets as well as metal coatings. The composites have low wear, electromagnetic material save, and high corrosion resistance. My research group, Changlei Xia and colleagues, introduced aluminum sheets into hemp fiber mats in a bid to produce sandwich-structure composites via vacuum assisted resin transfer molding method. We then analyzed the microstructures, electromagnetic interference shielding performances, and mechanical attributes of the hybrid composite. The work is published in Composites Part B.

We fabricated hybrid composites using hemp fiber mats, aluminum sheets and epoxy resin via the vacuum assisted resin transfer molding method. The electromagnetic interference shielding effectiveness was then conducted in an 8-12GHz frequency range. The results of the shielding measurements were presented in decibels.

The fabricated composites exhibited excellent electromagnetic interference shielding performances after introducing one aluminum sheet into two fiber-based composites or two aluminum sheets in three natural fiber-based composite layers. The electromagnetic interference shielding effectiveness of the composites, in the 8-12 GHz frequency range were observed to increase from 1.0-4.8dB to 30.7-46.8dB after introducing aluminum sheet layer. The values also increased from 1.4-6.3dB to 28.5-53.5dB after two layers of aluminum sheets were introduced in the three layers of the natural fiber-based composite.

The mechanical integrity of the hybrid composites did not reduce even after incorporating aluminum sheets as core materials. Interfacing bonding test results confirmed that the bonding between the fibers and the aluminum sheets was strong thanks to the vacuum assisted resin transfer molding fabrication process.

The aluminum sheets and the natural fiber-based hybrid composites have been identified in the study to have superior electromagnetic interference shielding performance with excellent mechanical attributes as good electromagnetic shielding materials.