Experimental investigation of cyclic thermomechanical deformation in torsion

An investigation of thermomechanical testing and deformation behavior of tubular specimens under torsional loading is described. Experimental issues concerning test accuracy and control specific to thermomechanical loadings under a torsional regime are discussed. A series of shear strain-controlled tests involving the nickel-base superalloy Hastelloy X were performed with various temperature excursions and compared to similar thermomechanical uniaxial tests. The concept and use of second invariants of the deviatoric stress and strain tensors as a means of comparing uniaxial and torsional specimens is also briefly presented and discussed in light of previous thermomechanical tests conducted under uniaxial conditions

Damping Characteristics of Carbon Nanotube-Epoxy Composites via Multiscale Analysis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83585/1/AIAA-2010-2896-684.pd

Detection of Composite Delaminations and Broken Solder Joints by a Full-Field Laser Doppler Technique

A method for full-field non-contact vibration measurement based on the Michelson Interferometer has been developed and applied to a wide range of components and structures. Unlike other optical techniques such as holography, the vibration imager does not require a specialized laboratory and stable environment, works over a much wider dynamic range,and the vibration time history is available for a more detailed analysis of the structures response. Use of this technique to detect delaminations in graphite/epoxy specimens is explored in this paper. The data was compared with X-ray and ultrasonic methods. The integrity of solder joints in electronic circuit boards has also been studied by this method at the University of Wisconsin, Madison and is also presented in this paper

Engineered Polymer Composites Through Electrospun Nanofiber Coating of Fiber Tows

Composite materials offer significant weight savings in many aerospace applications. The toughness of the interface of fibers crossing at different angles often determines failure of composite components. A method for toughening the interface in fabric and filament wound components using directly electrospun thermoplastic nanofiber on carbon fiber tow is presented. The method was first demonstrated with limited trials, and then was scaled up to a continuous lab scale process. Filament wound tubes were fabricated and tested using unmodified baseline towpreg material and nanofiber coated towpreg

On the fatigue response of a bonded repaired aerospace composite using thermography

Lock-in thermography was employed to investigate the repair efficiency of a bonded repaired aerospace composite subjected to step-wise cycling mechanical loading. The studied component (substrate) was artificially damaged with a 5 mm circular notch and subsequently repaired with a tapered bonded patch. Critical and sub-critical damage of the repaired component was monitored via thermography during 5 Hz tension–tension fatigue. The examination of the acquired thermographs enabled the identification of the patch debonding propagation as well as the quantification of the stress magnification at the patch ends and the locus of the circular notch. It was found that fatigue mechanical loading yields both thermoelastic and hysterestic phenomena with the latter being more prominent prior to the failure of the studied repaired component

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Detection of Composite Delaminations and Broken Solder Joints by a Full-Field Laser Doppler Technique

A method for full-field non-contact vibration measurement based on the Michelson Interferometer has been developed and applied to a wide range of components and structures. Unlike other optical techniques such as holography, the vibration imager does not require a specialized laboratory and stable environment, works over a much wider dynamic range,and the vibration time history is available for a more detailed analysis of the structures response. Use of this technique to detect delaminations in graphite/epoxy specimens is explored in this paper. The data was compared with X-ray and ultrasonic methods. The integrity of solder joints in electronic circuit boards has also been studied by this method at the University of Wisconsin, Madison and is also presented in this paper.</p

Microstructural development of SCS-6 SiC fibers during high temperature creep

Microstructural development of SCS-6 SiC fibers induced by creep deformation at 1400°C is presented. Grain growth occurs in all SiC regions of the fiber during creep. Portions of the SiC4 region transform from βSiC to αSiC growing at the expense of the βSiC. The SiC1 through SiC3 regions of the fiber consist of a distinct (C + βSiC) two-phase region. The grain growth of the βSiC grains in the two-phase region is not as extensive as in the SiC4 region, suggesting that the presence of excess carbon may inhibit the growth of βSiC