Composites characterizations

Oron [305] described dynamic evaluation of fracture mechanisms in composite materials by direct observation in the SEM. In this systematic study tensile loading of notched carbon fiber epoxy composites was conducted in the SEM. The three stages of fracture first described by Tetelman [306] are (1) the tip of the notch is blunted and microcracks form there, (2) micro- 

Conductive reinforcements in thermoplastics are a new application of composites [2891. High temperature resistant thermoplastics, such as PPS, PEI, PPO and liquid crystal polyesters, have been combined with conductive fibers, generally chopped graphite and nickel coated graphite. Fiber distribution, orientation and fracture morphology were determined by optical and SEM techniques. Poor bonding in the nickel coated graphite composite, as observed in SEM tensile fractures, resulted in lowered tensile and impact properties. 

Composites may also be examined by transmission EM methods, such as by bright field, dark field and electron diffraction of ultrathin sections. Sections of carbon fiber composites are quite difficult to obtain, but the technique is possible and has been described by Oberlin [309, 310]. Important information that can be obtained relates to the fiber-resin interface which is known to be critical to composite properties and is often adversely affected by environmental conditions. 

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J. M. Whitney, N. J. Pagano, and R. B. Pipes, Design and Fabrication of Tubuiar Specimens for Composite Characterization, in Composite Materials Testing and Design (Second Conference), H. T. Corten (Chairman), Anaheim, Caiifomia, 20-22 April 1971, ASTM STP 497, American Society for Testing and Materials, 1972, pp. 52-67. 

Baranski AS, Fawcett WR, Gatner K, Me Donald AC, MacDonald JR, Selen M (1983) Structural and compositional characterization of mixed CdS-CdSe films grown by cathodic electrodeposition. J Electrochem Soc 130 579-583... 

The latter report demonstrated the unique ability of this technique to resolve surface structure as well as surface composition at the electrified solid-liquid interfaces. In particular, STM has become an important tool for ex situ and in situ characterization of surfaces at the atomic level, in spite its significant limitations regarding surface composition characterization for bimetallic systems, such as the lack of contrast for different elements and the scanned surface area being too small to be representative for the entire surface. To avoid these limitations, STM has been mostly used as a complementary tool in surface characterization. 

Chemical Composition, Characterization, and Differentiation of Honey Botanical and Geographical Origins... 

D. H. Zhang, M. A. Kandadai, J. Cech, S. Roth, S. A. Curran, Poly(L-lactide) (PLLA)/multiwalled carbon nanotube (MWCNT) composite Characterization and biocompatibility evaluation, Journal of Physical Chemistry B, vol. 110, pp. 12910-12915, 2006. 

The results of these experiments indicate that EE may be used to detect microfracture events on the composite surface, and signal the early stages of composite failure. It also clarifies the source of AE as a function of strain by the presence or absence of AE-EE correlations, and allows more details of failure mechanisms and composite characterization to be obtained. 

In Ref. 9, no structural or compositional characterization was given CU2S was assumed. The films were not uniform and did not adhere to the substrates. The high values of resistivity are unusual for this material it may be that 10 -10 was intended. 

In Ref. 47, as before, no structural or compositional characterization was given, and the fihns were classified as Cuj S. Average grain size, measured by scanning electron microscopy (SEM), was ca. 70 nm. 

In Ref. 103, the pH of the bath was rather critical films deposited at pH > 10.5 were powdery and poorly adhering, while at pH < 9.5, no deposition was observed. No stractural or compositional characterization was given, but from the transmission spectrum it could be assumed that the film was SnS2 (and also highly scattering). 

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