Microcrack Analysis of Composite Materials

2010 ◽  
pp. 159-175
Keyword(s):  
Composite Materials ◽  
Polarized Light ◽  
Fatigue Loading ◽  
Dark Field ◽  
Field Analysis ◽  
Thermal Cycles ◽  
Dynamic Impact ◽  
Bright Field ◽  
Temperature Changes

Abstract The formation of microcracks in composite materials may arise from static-, dynamic-, impact-, or fatigue-loading situations and also by temperature changes or thermal cycles. This chapter discusses the processes involved in the various methods for the microcrack analysis of composite materials, namely bright-field analysis, polarized-light analysis, contrast dyes analysis, and dark-field analysis. The analysis of microcracked composites using epi-fluorescence is also covered. In addition, the chapter describes the procedures for the determination and recording of microcracks in composite materials.

Viewing the Specimen Using Reflected-Light Microscopy

2010 ◽  
pp. 89-114
Keyword(s):  
Composite Materials ◽  
Light Microscopy ◽  
Optical Microscopy ◽  
Polarized Light ◽  
Dark Field ◽  
Microscopy Technique ◽  
Reflected Light ◽  
Specific Analysis ◽  
Dark Field Illumination ◽  
Preparation Techniques

Abstract The analysis of composite materials using optical microscopy is a process that can be made easy and efficient with only a few contrast methods and preparation techniques. This chapter is intended to provide information that will help an investigator select the appropriate microscopy technique for the specific analysis objectives with a given composite material. The chapter opens with a discussion of macrophotography and microscope alignment, and then goes on to describe various illumination techniques that are useful for specific analysis requirements. These techniques include bright-field illumination, dark-field illumination, polarized-light microscopy, interference and contrast microscopy, and fluorescence microscopy. The chapter also provides a discussion of sample preparation materials such as dyes, etchants, and stains for the analysis of composite materials using optical microscopy.

Light Microscopy

1984 ◽  
pp. 267-333
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
Dark Field ◽  
Depth Of Field ◽  
Bright Field ◽  
Basic Physics ◽  
Dark Field Illumination ◽  
The Difference ◽  
Tools And Techniques ◽  
The Relationship

Abstract This chapter discusses the tools and techniques of light microscopy and how they are used in the study of materials. It reviews the basic physics of light, the inner workings of light microscopes, and the relationship between resolution and depth of field. It explains the difference between amplitude and optical-phase features and how they are revealed using appropriate illumination methods. It compares images obtained using bright field and dark field illumination, polarized and cross-polarized light, and interference-contrast techniques. It also discusses the use of photometers, provides best practices and recommendations for photographing structures and features of interest, and describes the capabilities of hot-stage and hot-cell microscopes.

Polymeric Composites, Morphological Characterization, and Fracture Analysis: fluorescent, dark field, bright field, and polarized light optical microscopy

2004 ◽  
Vol 10 (S02) ◽  
pp. 740-741 ◽  
Author(s):  
Luther M. Gammon
Keyword(s):  
Optical Microscopy ◽  
Polarized Light ◽  
Polymeric Composites ◽  
Fracture Analysis ◽  
Morphological Characterization ◽  
Dark Field ◽  
Bright Field ◽  
Light Optical Microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Metallography Parameters Study of Fe-6.5wtSi Alloy Obtained by Spray Forming

2008 ◽  
Vol 591-593 ◽  
pp. 315-321
Author(s):  
F.L. Rodrigues ◽  
M.A. Soares ◽  
Maria do Carmo Silva ◽  
Claudemiro Bolfarini ◽  
M.D.C. Sobral
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Silicon Content ◽  
Room Temperature ◽  
Core Loss ◽  
Polarized Light ◽  
Spray Forming ◽  
Dark Field ◽  
Bright Field ◽  
Silicon Iron

Silicon-iron alloys with silicon content about 6.5wt.%Si offer a great potential for applications aiming reduction of core loss in electric parts. Deposits of the Fe-6.5wt%Si alloy produced by spray forming were annealed at temperatures between 400 and 1300oC, during 1h in vacuum. The grain size has a great importance to the magnetic properties. In the present work, it was analyzed the influence of the metallography parameters in order to get the best accuracy to determine the grain size according to ASTM 112-96. Chemical composition, time and temperature of specific etchings were modified and tested in different conditions of observation in light microscopy. Bright field, polarized light and dark field were used in the samples aiming to measure the grain size. The best etchings were Nital 10% and Marshall, both at room temperature. The results of grain measurement are presented in their relationship with the magnetic properties.

Micromechanical Modeling of Multifunctional Composites

2012 ◽  
Author(s):  
Yehia Bahei-El-Din ◽  
Amany Micheal
Keyword(s):  
Composite Materials ◽  
Local Fields ◽  
Field Analysis ◽  
Micromechanical Modeling ◽  
Current Application ◽  
Temperature Changes ◽  
Ambient Temperatures ◽  
Material Development ◽  
Analysis Scheme ◽  
And Performance

In the new generation of aircrafts in which the use of composite materials is ever increasing, smart composites reinforced with active fibers are expected to play a major role in monitoring health and performance of the airframe in addition to their load carrying capabilities. While advancements in material development, e.g. PZT filaments, bring the fabrication of structural components with multifunctionality closer to reality, reliable predictions of their behavior and performance are lacking. In particular, the modeling of damage progression on multiple lengthscales in structural composites is essential in modeling both sensing and/or actuation functionalities. Moreover, temperature changes affect the response of active constituents through changes in thermomechanical fields and/or changes in coupled functions, as for example in pyroelectric materials. These complexities invite a novel modeling approach of the problem. This paper represents a major departure from present approaches, which focus mainly on undamaged, unidirectionally reinforced multifunctional fibrous composites at ambient temperatures. The work presented models multifunctional composite materials and structures on multiscales considering piezoelectric and pyroelectric phenomena. In particular, fibrous laminates with a general layup are considered under membrane forces and bending moments in combination with temperature changes. The solution for the local fields and overall response is determined in terms of a transformation field analysis scheme in which the local stresses or strains that cannot be removed by mechanical unloading are treated as eigen fields applied in an otherwise elastic medium. In the current application, the latter represents an aggregate of unidirectional plies and their phases. The proposed modeling strategy is applied to fibrous laminates subjected to mechanical and/or thermal loads. While the modeling of damage follows the same strategy, it is discussed elsewhere.

scholarly journals OPTICAL EFFECTS AT METALLIC AND NONMETALLIC MATERIALS MICROSCOPY

2018 ◽  
pp. 119-125
Author(s):  
A. G. Anisovich
Keyword(s):  
Surface Defects ◽  
Polarized Light ◽  
Uniaxial Crystal ◽  
Dark Field ◽  
Bright Field ◽  
Visual Classification ◽  
Optical Effects ◽  
Dark Field Illumination ◽  
Transparent Materials

Optical effects arising on surface defects of metals, alloys and transparent materials are discovered in conditions of various illumination such as dark-field and bright-field illumination as well as polarized light. It is shown that the methods of optical contrasting let it possible to determine surface defects of metallic and nonmetallic materials as well as defects inside optically transparent materials. The connection between optical effects and design features of lens by the use of dark-field illumination was shown. It is established that picture generation of spherical defect came about by analogy to uniaxial crystal by the study using polarized light. The schematic diagram of optical effects for various materials to make visual classification of surface defects is suggested.

Microstructural Characterization of CP Steel Used in Automotive Industry

2014 ◽  
Vol 775-776 ◽  
pp. 141-145 ◽  
Author(s):  
Erica Dias ◽  
Laís Horimoto ◽  
Marcelo dos Santos Pereira
Keyword(s):  
Automotive Industry ◽  
Polarized Light ◽  
Microstructural Characterization ◽  
Dark Field ◽  
Metallographic Analysis ◽  
Sodium Metabisulfite ◽  
Bright Field ◽  
Complex Phase ◽  
Dark Field Illumination

This study aims to characterize the microstructure of the complex phase steel (CP). Using the conventional and colored metallographic analysis with 3% Nital etchant, sodium metabisulfite 10% and LePera. Techniques were applied in this work of optical microscopy, using, besides the lighting in bright field, dark field illumination of the reverse contrast in bright field illumination, the method of polarized light, which generates colorful contrast, providing a complementary identification phases present in the microstructure, and the system by differential interference contrast (DIC). The results obtained by metallography CP indicates that the steel has a microstructure composed of ferrite, retained austenite, bainite and martensite and precipitates arranged in a refined and complex morphology. Besides bright field illumination others optical microscopys techniques such as dark field illumination were applied.

Two Investigations into Grain Boundary Structure

1977 ◽  
Vol 35 ◽  
pp. 688-691
Author(s):  
P. Humble
Keyword(s):  
Grain Boundary ◽  
Dark Field ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Bright Field ◽  
Intrinsic Structure ◽  
Weak Beam ◽  
Grain Boundary Structure ◽  
Independent Information ◽  
Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

Imaging of platinum-shadowed macromolecular complexes in dark field

1984 ◽  
Vol 42 ◽  
pp. 146-147
Author(s):  
D.W. Andrews ◽  
F.P. Ottensmeyer
Keyword(s):  
Thin Film ◽  
Three Dimensional ◽  
Average Diameter ◽  
Dark Field ◽  
Bright Field ◽  
Field Mode ◽  
Macromolecular Complexes ◽  
Average Mass ◽  
Topological Features ◽  
Projection Images

Shadowing with heavy metals has been used for many years to enhance the topological features of biological macromolecular complexes. The three dimensional features present in directionaly shadowed specimens often simplifies interpretation of projection images provided by other techniques. One difficulty with the method is the relatively large amount of metal used to achieve sufficient contrast in bright field images. Thick shadow films are undesirable because they decrease resolution due to an increased tendency for microcrystalline aggregates to form, because decoration artefacts become more severe and increased cap thickness makes estimation of dimensions more uncertain.The large increase in contrast provided by the dark field mode of imaging allows the use of shadow replicas with a much lower average mass thickness. To form the images in Fig. 1, latex spheres of 0.087 μ average diameter were unidirectionally shadowed with platinum carbon (Pt-C) and a thin film of carbon was indirectly evaporated on the specimen as a support.

A Many-Beam Technique for Enhanced Resolution of Partial Dislocations

1972 ◽  
Vol 30 ◽  
pp. 646-647
Author(s):  
J. M. Oblak ◽  
B. H. Kear
Keyword(s):  
Phase Shift ◽  
Field Method ◽  
Dark Field ◽  
Bright Field ◽  
Field Technique ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Enhanced Resolution ◽  
Nickel Base ◽  
Beam Technique

The “weak-beam” and systematic many-beam techniques are the currently available methods for resolution of closely spaced dislocations or other inhomogeneities imaged through strain contrast. The former is a dark field technique and image intensities are usually very weak. The latter is a bright field technique, but generally use of a high voltage instrument is required. In what follows a bright field method for obtaining enhanced resolution of partial dislocations at 100 KV accelerating potential will be described.A brief discussion of an application will first be given. A study of intermediate temperature creep processes in commercial nickel-base alloys strengthened by the Ll2 Ni3 Al γ precipitate has suggested that partial dislocations such as those labelled 1 and 2 in Fig. 1(a) are in reality composed of two closely spaced a/6 <112> Shockley partials. Stacking fault contrast, when present, tends to obscure resolution of the partials; thus, conditions for resolution must be chosen such that the phase shift at the fault is 0 or a multiple of 2π.

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