On Harmonic Waves in Layered Composites

1977 ◽  
Vol 44 (4) ◽  
pp. 689-695 ◽  
Author(s):  
S. Minagawa ◽  
S. Nemat-Nasser
Keyword(s):  
Dispersion Relations ◽  
Harmonic Waves ◽  
Layered Composites ◽  
Fiber Reinforced ◽  
Elastic Composite ◽  
Elastic Composites ◽  
Special Case ◽  
Layer Problem

For harmonic waves propagating in a layered elastic composite, approximate dispersion relations are developed. Both waves propagating in the direction of the layers, and those propagating obliquely to this direction, are considered. The layer problem is treated as a special case of fiber-reinforced elastic composites. For illustration, the approximate results are compared with the exact ones for the special case of homogeneous layers.

Harmonic Waves in Fiber-Reinforced Orthotropic Elastic Composites

1981 ◽  
Vol 48 (4) ◽  
pp. 967-971 ◽  
Author(s):  
S. Nemat-Nasser ◽  
M. Yamada
Keyword(s):  
Dispersion Curves ◽  
Orthotropic Materials ◽  
Harmonic Waves ◽  
Fiber Reinforced ◽  
Dispersive Property ◽  
Elastic Composites

The dispersive property of fiber-reinforced elastic composites consisting of orthotropic materials is studied. Based on a new quotient recently proposed by one of the authors, approximate dispersion curves are obtained, and the influence of anisotropy is illustrated.

Harmonic Waves in Layered Composites: Comparison Among Several Schemes

1975 ◽  
Vol 42 (3) ◽  
pp. 699-704 ◽  
Author(s):  
S. Nemat-Nasser ◽  
S. Minagawa
Keyword(s):  
Rayleigh Quotient ◽  
Upper Bounds ◽  
Harmonic Waves ◽  
Layered Composites ◽  
Test Functions ◽  
Lower And Upper Bounds ◽  
Numerical Examples ◽  
Elastic Composites

For harmonic waves in layered elastic composites the results obtained by means of the Rayleigh quotient based on displacement and the Rayleigh quotient based on stress, are compared with those obtained by a new quotient recently proposed by one of the authors, in an effort to examine reasons for the astonishing accuracy of the new quotient for this class of problems. This comparison leads to a scheme for obtaining improved test functions which then give very accurate lower and upper bounds for the wave frequencies. Results are illustrated by numerical examples.

Selected mechanical properties of the reinforced layered composites

2021 ◽  
Vol 113 ◽  
pp. 53-59
Author(s):  
Izabela Burawska-Kupniewska ◽  
Maciej borowski
Keyword(s):  
Mechanical Properties ◽  
Reference Material ◽  
Density Profile ◽  
Natural Fibres ◽  
Reinforced Composites ◽  
Layered Composites ◽  
Fiber Reinforced ◽  
Linen Fabric ◽  
Core Materials

Selected mechanical properties of the reinforced layered composites. Publication concerns the production of fiber reinforced layered composites and its selected mechanical properties. The following reinforcement types of the layered composites were taken into consideration: linen fabric and fiberglass. Two types of core materials were tested: plywood and PUR foam. The assembled composites were tested for MOR, MOE and screw holding ability. Additionally density and density profile were determined. Fiberglass reinforced composites were used as a reference material for composites reinforced with natural fibres.

Wave Propagation and Parametric Instability in Materials Reinforced by Fibers With Periodically Varying Directions

1975 ◽  
Vol 42 (4) ◽  
pp. 825-831 ◽  
Author(s):  
M. Schoenberg ◽  
Y. Weitsman
Keyword(s):  
Composite Material ◽  
Wave Propagation ◽  
Elastic Medium ◽  
Parametric Instability ◽  
Transversely Isotropic ◽  
Harmonic Waves ◽  
Fiber Reinforced ◽  
Frequency Bands ◽  
Structural Periodicity ◽  
Dominant Direction

This paper concerns the propagation of plane harmonic waves in an infinite fiber-reinforced elastic medium. The composite material is represented by an equivalent homogeneous transversely isotropic matter whose preferred directions coincide with the orientations of the fibers. The fibers are assumed to wobble periodically about a dominant direction, all fibers being parallel to each other. This wobbliness endows the material with a structural periodicity which generates dispersion at all frequencies and instability for various frequency bands. The zones of instability are analyzed in some detail.

Large enhancement of phononic gap in periodic and quasiperiodic elastic composites by using air inclusions

2005 ◽  
Vol 220 (9-10) ◽  
Author(s):  
Yun Lai ◽  
Zhao-Qing Zhang
Keyword(s):  
Potential Energy ◽  
Two Dimensions ◽  
Large Enhancement ◽  
Elastic Composite ◽  
Elastic Composites

AbstractWe find that a phononic gap in a periodic or quasiperiodic elastic composite can be significantly enhanced by inserting air inclusions into the systems. The positions of the insertion are chosen to suppress the shear potential energy of the acoustical branches and lower their frequencies. This is demonstrated in two dimensions. Gap positions and sizes as functions of the radii of the air cylinders for systems of aluminum cylinders in epoxy and steel cylinders in epoxy are presented for both triangular and 12-fold quasiperiodic lattices.

Harmonic Waves in Layered Composites: Bounds on Frequencies

1974 ◽  
Vol 41 (1) ◽  
pp. 288-290 ◽  
Author(s):  
S. Nemat-Nasser ◽  
F. C. L. Fu
Keyword(s):  
Harmonic Waves ◽  
Layered Composites

Variational Methods for Dispersion Relations and Elastic Properties of Composite Materials

1972 ◽  
Vol 39 (2) ◽  
pp. 327-336 ◽  
Author(s):  
W. Kohn ◽  
J. A. Krumhansl ◽  
E. H. Lee
Keyword(s):  
Composite Materials ◽  
Elastic Properties ◽  
Elastic Waves ◽  
Variational Principles ◽  
Lattice Structure ◽  
Dispersion Relations ◽  
Bravais Lattice ◽  
Layered Composites ◽  
Crystal Lattices ◽  
Ritz Procedure

The propagation of harmonic elastic waves through composite media with a periodic structure is analyzed. Methods utilizing the Floquet or Bloch theory common in the study of the quantum mechanics of crystal lattices are applied. Variational principles in the form of integrals over a single cell of the composite are developed, and applied in some simple illustrative cases. This approach covers waves moving in any direction relative to the lattice structure, and applies to structures of the Bravais lattice groups which include, for example, parallel rods in a square or hexagonal pattern, and an arbitrary parallelepiped cell. More than one type of inclusion can be considered, and the elastic properties and density of the inclusion and matrix can vary with position, as long as they are periodic from cell to cell. The Rayleigh-Ritz procedure can be applied to the solution of the variational equations, which provides a means of calculating dispersion relations and elastic properties of specific composite materials. Detailed calculations carried out on layered composites confirm the effectiveness of the method.

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