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.

About the author

Sheldon Q. Shi, Ph.D.
Professor and Group Leader in Renewable Bioproducts Manufacturing,
Mechanical and Energy Engineering Department, University of North Texas (UNT).
3940 N Elm Suite F101, Denton, Texas 76207-7102
Phone: 940-369-5930; Fax: 940-369-8675; Email: [email protected]

Dr. Sheldon Shi obtained his Ph.D. degree at Michigan Technological University (MTU) in 1997.  After about two-year research experience as a Post-Doctorate Research Associate at both MTU and University of Maine, he joined APA – The Engineered Wood Association in 1999 as a Engineer conducting product evaluation and quality assurance of engineered wood based products for building construction.  In 2004, he joined the faculty at Mississippi State University (MSU) as an Assistant Professor and received tenure.  After seven years of service with MSU, Dr. Shi joined the University of North Texas in Mechanical and Energy Engineering Department.

Dr. Shi has been experienced in the manufacture processes of composite materials using biomass as feedstock, such as wood, plant fibers, soybean, etc. His expertise is on the processing and evaluation of the bio-based composites, functional composites, bio-based adhesive, and adhesion/bond durability of the composite materials.  Dr. Shi has been serving as PI and Co-PI for Federal projects including DOE, NSF, and USDA.  Dr. Shi received multiple best paper and research awards in his career.  He is appointed as an Adjunct Professor at Northeast Forestry University, Harbin, China and Guangxi University, Nanning, China; Longjiang Scholar in Heilongjiang province, China; Ph.D. Dissertation Examiner for Deakin University, Australia, and Advisory Board and Adjunct Scientist at the International Center for Bamboo and Rattan (ICBR), Beijing, China.

He served as Executive Board member for the Society of Wood Science and Technology (SWST) during 2008 – 2015, and was voted as the President for the society during 2013 – 2014; He is on the Editor Board for a few journals, such as “International Journal of Environmental Engineering and Natural Resources and ISBN Thermodynamics. He has been serving panel reviewer for United State Department of Agriculture (USDA) and Department of Energy (DOE) proposals and more than 40 professional journals, standard organizations. Dr. Shi has published over 180 papers, from which over 130 are in SCI peer-reviewed journals.


Changlei Xia, Jason Yu, Sheldon Q. Shi, Ying Qiu, Liping Cai, H. Felix Wu, Han Ren, Xu Nie, Hualiang Zhang. Natural fiber and aluminum sheet hybrid composites for high electromagnetic interference shielding performance. Composites Part B, volume 114 (2017), pages 121-127.


Go To Composites Part B: Engineering 

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