scholarly journals Thermal/Mechanical Response and Damage Growth in Polymeric Composites at Cryogenic Temperatures

2002 ◽  
Author(s):  
Karen Whitley ◽  
Thomas Gates
Keyword(s):  
Mechanical Response ◽  
Polymeric Composites ◽  
Cryogenic Temperatures ◽  
Damage Growth

Modeling Damage Growth in Oxidized High-Temperature Polymeric Composites

JOM ◽  
2012 ◽  
Vol 65 (2) ◽  
pp. 246-255 ◽  
Author(s):  
Nan An ◽  
Kishore Pochiraju
Keyword(s):  
High Temperature ◽  
Polymeric Composites ◽  
Damage Growth

scholarly journals THERMAL-MECHANICAL RESPONSE OF CRACKED SATIN WEAVE CFRP COMPOSITES AT CRYOGENIC TEMPERATURES

2008 ◽  
Author(s):  
S. Watanabe ◽  
Y. Shindo ◽  
F. Narita ◽  
T. Takeda ◽  
U. (Balu) Balachandran ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Cryogenic Temperatures ◽  
Cfrp Composites

Damage Coupled With Heat Conduction in Uniaxially Reinforced Composites

1988 ◽  
Vol 55 (3) ◽  
pp. 641-647 ◽  
Author(s):  
Y. Weitsman
Keyword(s):  
Heat Conduction ◽  
Mechanical Response ◽  
Internal State ◽  
Constitutive Relations ◽  
Damage Model ◽  
Irreversible Thermodynamics ◽  
Continuum Damage ◽  
State Variables ◽  
Damage Growth ◽  
Continuum Damage Model

This paper presents a continuum damage model for a unidirectionally reinforced composite based upon fundamental concepts of continuum mechanics and irreversible thermodynamics. Damage is incorporated by two symmetric, second-rank, tensor-valued, internal state variables which represent the total areas of “active” and “passive” cracks contained within a representative material volume element. Constitutive relations are derived for both the mechanical response and heat flux in the presence of damage. It is shown that damage growth contributes to dissipation in the coupled heat conduction process. A specific fracture mechanics solution is employed to relate “microlevel” crack growth processes to “macrolevel” damage growth expressions. This approach lends itself to a probabilistic formulation of the continuum damage model.

scholarly journals NUMERICAL MODELLING OF THE AIRFRAME DAMAGE GROWTH FOR THE ADHESIVE REPAIR JOINT CALCULATION

2018 ◽  
Vol 21 (3) ◽  
pp. 125-138
Author(s):  
A. A. Fedotov ◽  
A. V. Tsipenko ◽  
A. I. Lebedev
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Information Technologies ◽  
Mechanical Response ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Fatigue Properties ◽  
Damage Growth ◽  
Finite Element Software ◽  
Software Packages

In the context of the predicted growth in air transportation, the additional attention will be paid to the organization of the competitive maintenance and repair operations for the commercial airplanes. The implementation of new technological processes for airframe repairs and the application of modern information technologies during the development of the repair procedures can be a significant advantage in the expanding market of post-production support of the commercial air fleet. Airframe adhesive repairs allow using lifting abilities of the materials more intensively, but application of the adhesive joints technology requires more complicated strength calculation procedure. It is advisable to utilize the modern finite element software packages to perform the reliable calculation. The capabilities of these software packages allow obtaining adequate computational results for adhesive repair joint parameters subjected to cyclic loads. This paper is concentrated on application of the finite element methods to simulate the crack growth in isotropic material and on methods for accelerated calculation of the mechanical response of cracked structures. Crack growth simulation is performed based on XFEM methods where the created finite element model is complemented with asymptotic imitation function of crack tip and with discontinuous jump function across the crack surfaces. Fatigue properties of the repair joint are modelled in accordance with direct cyclic approach, where a Fourier series approximation with time integration of the nonlinear material behavior is applied. After that, the result of integration at each point of the load history is used for the prediction of the material fatigue properties degradation at the next step of computation; this allows us to evaluate the material damage growth rate. Based on calculation results, a conclusion was made that the received numerical data match the full-scale test results; the time spent for calculation with the usage of accelerated computational methods was evaluated. 

An Experimental Study of the Mechanical Response of Frozen Biological Tissues at Cryogenic Temperatures

Cryobiology ◽  
1996 ◽  
Vol 33 (4) ◽  
pp. 472-482 ◽  
Author(s):  
YOED RABIN ◽  
Paul S. Steif ◽  
Michael J. Taylor ◽  
Thomas B. Julian ◽  
Norman Wolmark
Keyword(s):  
Experimental Study ◽  
Mechanical Response ◽  
Biological Tissues ◽  
Cryogenic Temperatures

Cryogenic atomic force microscopy

1991 ◽  
Vol 49 ◽  
pp. 54-55
Author(s):  
K. A. Fisher ◽  
M. G. L. Gustafsson ◽  
M. B. Shattuck ◽  
J. Clarke
Keyword(s):  
Room Temperature ◽  
Rapid Freezing ◽  
Cryogenic Temperatures ◽  
Soft Or ◽  
Electrically Conductive ◽  
Force Microscopy ◽  
Flexible Molecules ◽  
Advantages And Disadvantages ◽  
Atomic Force ◽  
Chemical Perturbation

The atomic force microscope (AFM) is capable of imaging electrically conductive and non-conductive surfaces at atomic resolution. When used to image biological samples, however, lateral resolution is often limited to nanometer levels, due primarily to AFM tip/sample interactions. Several approaches to immobilize and stabilize soft or flexible molecules for AFM have been examined, notably, tethering coating, and freezing. Although each approach has its advantages and disadvantages, rapid freezing techniques have the special advantage of avoiding chemical perturbation, and minimizing physical disruption of the sample. Scanning with an AFM at cryogenic temperatures has the potential to image frozen biomolecules at high resolution. We have constructed a force microscope capable of operating immersed in liquid n-pentane and have tested its performance at room temperature with carbon and metal-coated samples, and at 143° K with uncoated ferritin and purple membrane (PM).

Comparison of Substructures Between Uniaxial and Biaxial Deformation in 1100-0 Aluminum

1981 ◽  
Vol 39 ◽  
pp. 52-53
Author(s):  
D. L. Rohr ◽  
S. S. Hecker
Keyword(s):  
Plastic Strain ◽  
Cell Walls ◽  
Room Temperature ◽  
Mechanical Response ◽  
Biaxial Tension ◽  
Initial Deformation ◽  
Uniaxial Deformation ◽  
Biaxial Deformation ◽  
Stress States ◽  
Comprehensive Study

As part of a comprehensive study of microstructural and mechanical response of metals to uniaxial and biaxial deformations, the development of substructure in 1100 A1 has been studied over a range of plastic strain for two stress states.Specimens of 1100 aluminum annealed at 350 C were tested in uniaxial (UT) and balanced biaxial tension (BBT) at room temperature to different strain levels. The biaxial specimens were produced by the in-plane punch stretching technique. Areas of known strain levels were prepared for TEM by lapping followed by jet electropolishing. All specimens were examined in a JEOL 200B run at 150 and 200 kV within 24 to 36 hours after testing.The development of the substructure with deformation is shown in Fig. 1 for both stress states. Initial deformation produces dislocation tangles, which form cell walls by 10% uniaxial deformation, and start to recover to form subgrains by 25%. The results of several hundred measurements of cell/subgrain sizes by a linear intercept technique are presented in Table I.

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

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