Elastomeric composites with tuned electromagnetic characteristics

• Published in: Smart materials and structures 2013-01, Vol.22 (1), p.15006-1-6
• Main Authors: Wheeland, Sara, Bayatpur, Farhad, Amirkhizi, Alireza V, Nemat-Nasser, Sia
• Format: Article
• Language: English
• Subjects: Applied sciences; Arrays; Axial strain; Chirality; Coiling; Composites; Deformation; Elastomers; Exact sciences and technology; Forms of application and semi-finished materials; Handedness; Polymer industry, paints, wood; Technology of polymers; Tuning
• ISSN: 0964-1726; 1361-665X
• DOI: 10.1088/0964-1726/22/1/015006

This paper presents a novel elastomeric composite that exhibits a deformation-induced change in chirality. Previous efforts primarily dealt with a coil array in air without chiral tuning. Here, a composite is created that consists of an array of parallel, metallic helices of the same handedness embedded in a polymer matrix. The chiral response of the composite depends on pitch, coil diameter, wire thickness and coil spacing; however, pitch has the greatest effect on electromagnetic performance. The present study explores this effect by using helical elements to construct a chiral medium that can be mechanically stretched to adjust pitch. This adjustment directly affects the overall chirality of the composite. A prototype sample of the composite, fabricated for operation between 5.5-12.5 GHz, demonstrates repeatable elastic deformation. Using a transmit/receive measurement setup, the composite scattering response is measured over the frequency interval. The results indicate substantial tuning of chirality through deformation. An increase in axial strain of up to 30% yields a ∼18% change in axial chirality.