42856 Critical angle measurement of elastic constants in composite material

1994 ◽  
Vol 27 (1) ◽  
pp. 52
Keyword(s):  
Composite Material ◽  
Elastic Constants ◽  
Critical Angle ◽  
Angle Measurement

On: “RECENT TECHNIQUES FOR DETERMINATION OF IN SITU ELASTIC PROPERTIES AND MEASUREMENT OF MOTION AMPLIFICATION IN LAYERED MEDIA,” BY R.J. SWAIN (GEOPHYSICS, APRIL, 1962, PP. 237–241).

Geophysics ◽  
1963 ◽  
Vol 28 (1) ◽  
pp. 112-112 ◽  
Author(s):  
Harry R. Nicholls
Keyword(s):  
Elastic Properties ◽  
Elastic Constants ◽  
Design Problem ◽  
Critical Angle ◽  
Specific Design ◽  
Design Problems ◽  
Relative Value ◽  
Angle Method

Although I am in general agreement with Mr. Swain’s paper, there are several pitfalls inherent in the use of dynamic elastic constants which should not be ignored. The strength of materials and the elastic properties both undoubtedly depend on the rate of loading and/or the stress levels involved. It does not seem appropriate, therefore, to use dynamic in situ elastic properties for static design problems. The specific design problem at hand should determine the relative value placed on the use of static or dynamic elastic constants. The dynamic in situ values are generally more reliable than those obtained in the laboratory as indicated by Mr. Swain, although continued development of the laboratory pulse and critical‐angle method shows promise of improving the reliability of laboratory values.

scholarly journals Optimization of composite revolution shell by methods of theory of the optimal process

2020 ◽  
Vol 26 (5) ◽  
pp. 28-37
Author(s):  
A.P. Dzyuba ◽  
◽  
V.N. Sirenko ◽  
D.V. Klymenko ◽  
L.D. Levytina ◽  
...  
Keyword(s):  
Composite Material ◽  
Elastic Constants ◽  
Equations Of State ◽  
Experimental Testing ◽  
Necessary Optimality Conditions ◽  
Middle Surface ◽  
Variable Coefficients ◽  
Space Technology ◽  
Fiber Winding ◽  
Revolution Shell

We considered the problem of weight optimization of parameters of multi-layer composite shell produced by the method of continuous cross-winding under axisymmetric loading. Shell layers are placed symmetrically relative to the middle surface. The angles of the reinforcing material winding variable along the meridian and the thickness of layers are taken as the variation parameters. We propose an algorithm of the automated determination of the elastic constants of a composite material variable along the shell meridian anisotropy. The connection of the composite structure with the technological process of shell manufacturing by winding with a reinforcing tape under different angles to the axis of rotation is taken into account. The values of four elastic constants obtained as a result of experimental testing of witness specimens of the composite material along and orthogonal to the reinforcement are used as output. The equations of state of the moment theory of shells of the variable along the meridian orthotropy and wall thickness are obtained as a boundary value problem for a system of ordinary differential equations with variable coefficients. The use of the necessary optimality conditions in the form of the principle maximum of Pontryagin in the presence of arbitrary phrasal restraints made it possible to reduce the emerging multiparameter problem to a sequence of extreme problems of a significantly smaller dimension. This approach greatly simplifies taking into account the conditions of strength reliability, and technological and structural requirements of real design, and the process of finding an optimal project as a whole. The results of the optimization of a two-layer fiberglass shell of rotation are presented in the form of a change in the distribution of layers’ thickness and the glass fiber winding angle. Materials of research can be used to reduce the material consumption of structural elements in rocket and space technology and other branches.

TRANSMISSION OF SOUND THROUGH THIN PLATES

1939 ◽  
Vol 17a (9) ◽  
pp. 179-193 ◽  
Author(s):  
F. H. Sanders
Keyword(s):  
Satisfactory Agreement ◽  
Elastic Constants ◽  
High Frequency ◽  
Critical Angle ◽  
Wave Length ◽  
Thin Plates ◽  
Recent Theory ◽  
Transverse Waves ◽  
Longitudinal Waves ◽  
High Frequency Sound

The transmission of high frequency sound through plates of brass and nickel has been studied for angles of incidence ranging from 0 to 70 degrees, using effective plate thicknesses varying from one-twentieth of a wave-length to one wave-length. In addition to strong transmissions in the region below the normal critical angle, very sharp and intense transmission maxima are observed at angles of incidence greatly in excess of the critical angle. These transmission maxima fall within three clearly denned angular regions: (i) angles between zero and the critical angle for longitudinal waves; (ii) angles between the critical angle for longitudinal waves and the critical angle for transverse waves; and (iii) angles above the critical angle for transverse waves. In Regions (i) and (ii) the observed data are in satisfactory agreement with a recent theory advanced by Reissner, and good values of the elastic constants are obtained. By an extension of Lamb's theory for flexural vibrations in bars the results in Region (iii) can be interpreted.

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