Electrically tunable photonic crystals with nonlinear composite materials

2007 ◽  
Vol 91 (19) ◽  
pp. 191117 ◽  
Author(s):  
G. Wang ◽  
J. P. Huang ◽  
K. W. Yu
Keyword(s):  
Composite Materials ◽  
Photonic Crystals ◽  
Nonlinear Composite

A New Failure Criterion for Nonlinear Composite Materials

1994 ◽  
Vol 16 (2) ◽  
pp. 138 ◽  
Author(s):  
WS Johnson ◽  
JE Masters ◽  
TK O'Brien ◽  
GA Abu-Farsakh ◽  
YA Abdel-Jawad
Keyword(s):  
Composite Materials ◽  
Failure Criterion ◽  
Nonlinear Composite

scholarly journals Fully optimized second-order variational estimates for the macroscopic response and field statistics in viscoplastic crystalline composites

2015 ◽  
Vol 471 (2184) ◽  
pp. 20150665 ◽  
Author(s):  
P. Ponte Castañeda
Keyword(s):  
Composite Materials ◽  
Variational Principle ◽  
Variational Method ◽  
Single Crystal ◽  
Second Order ◽  
Duality Gaps ◽  
Nonlinear Composite ◽  
Constitutive Response ◽  
Correction Terms ◽  
Macroscopic Response

A variational method is developed to estimate the macroscopic constitutive response of composite materials consisting of aggregates of viscoplastic single-crystal grains and other inhomogeneities. The method derives from a stationary variational principle for the macroscopic stress potential of the viscoplastic composite in terms of the corresponding potential of a linear comparison composite (LCC), whose viscosities and eigenstrain rates are the trial fields in the variational principle. The resulting estimates for the macroscopic response are guaranteed to be exact to second order in the heterogeneity contrast, and to satisfy known bounds. In addition, unlike earlier ‘second-order’ methods, the new method allows optimization with respect to both the viscosities and eigenstrain rates, leading to estimates that are fully stationary and exhibit no duality gaps. Consequently, the macroscopic response and field statistics of the nonlinear composite can be estimated directly from the suitably optimized LCC, without the need for difficult-to-compute correction terms. The method is applied to a simple example of a porous single crystal, and the results are found to be more accurate than earlier estimates.

Polychromatic Composite Films for Adaptive Camouflage

2014 ◽  
Author(s):  
Ian O. Gent ◽  
Annela M. Seddon ◽  
Nicholas W. Roberts ◽  
Richard S. Trask
Keyword(s):  
Optical Properties ◽  
Composite Materials ◽  
Photonic Crystals ◽  
Composite Films ◽  
Colour Change ◽  
Preliminary Results ◽  
Photonic Structures ◽  
Material Solution

Having the correct camouflage for the current surroundings increases the safety of personnel and can provide a tactical advantage. However, theatres of war are rarely homogeneous and this leads to a compromise in order for the pattern to work in different subsets. In this work we take inspiration from the photonic structures found in insects to produce elastomeric composite materials with embedded photonic crystals that suggest a material solution for an adaptive camouflage system. Colour change for these materials is effected through mechanical straining of the produced composite. The procedure used to make these materials is detailed and preliminary results from testing of the mechanical and optical properties that these materials exhibit is presented.

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