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Title: Elastic waves in structurally chiral composites

Elastic wave propagation through structurally chiral (handed) media was studied. The primary objectives are to construct structurally chiral composites and to characterize their properties. Structurally chiral composites are constructed by stacking identical uniaxial plates, whose consecutive symmetric axes describe either a right- or a left-handed spiral. A matrix representation method is used to solve the elastic wave propagation in such layered composites. Numerical computation of the plane wave reflection and transmission characteristics for chiral arrangements are compared with those for the non-chiral one. It is concluded that the co-polarized characteristics are unaffected by the structural chirality, while the cross-polarized reflected and transmitted fields are greatly influenced by it. Numerical modeling is also applied for the real samples. The polarization ellipse of the transmitted field of each sample is calculated. To verify the form chirality, four glass-reinforced chiral and non-chiral composite samples are made from helix tape, molded, debulked, and cured individually under identical temperature and pressure histories. The spiral composites are characterized using shear and longitudinal wave transducers in ultrasonic experiments. Both the material properties and the polarization ellipse of the transmitted field of each sample are measured. It is proved conclusively that left and right handedness in the microstructuresmore » of a material rotates the plane of polarization of a propagating shear wave in the opposite directions. Thus it is now possible to say that by reducing the length scale of the handed microstructures tone more appropriate to its propagating wavelength, a medium is obtained that gives rise to effects similar to optical radar and optical dichroism.« less
Authors:
Publication Date:
OSTI Identifier:
5853561
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Ph.D. Thesis
Publisher:
University Park, PA (US); Pennsylvania State Univ.
Research Org:
Pennsylvania State Univ., University Park, PA (USA). Davey Lab.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COMPOSITE MATERIALS; WAVE PROPAGATION; MATHEMATICAL MODELS; MATRICES; MICROSTRUCTURE; POLARIZATION; S WAVES; SYMMETRY; CRYSTAL STRUCTURE; MATERIALS; PARTIAL WAVES 360603* -- Materials-- Properties