Nanocomposite Coating Mechanics via Piezospectroscopy

Coatings utilizing the piezospectroscopic (PS) effect of alpha alumina could enable on the fly stress sensing for structural health monitoring applications. While the PS effect has been historically utilized in several applications, here by distributing the photo-luminescent material in nanoparticle form within a matrix, a stress sensing coating is created. Parallel to developing PS coatings for stress sensing, the multi-scale mechanics associated with the observed PS response of nanocomposites and their coatings has been applied to give material property measurements, providing an understanding of particle reinforced composite behavior. Understanding the nanoparticle-coating-substrate mechanics is essential to interpreting the spectral shifts for stress sensing of structures. In the past, methods to experimentally measure the mechanics of these embedded nano inclusions have been limited, and much of the design of these composites depend on computational modeling and bulk response from mechanical testing. The PS properties of Chromium doped alumina allow for embedded inclusion mechanics to be revisited with unique experimental setups that probe the particles state of stress under applied load to the composite. These experimental investigations of particle mechanics will be compared to the Eshelby theory and its derivative theories in addition to the nanocomposite coating mechanics. This work discovers that simple nanoparticle load transfer theories are adequate for predicting PS properties in an intermediate volume fraction range. With fundamentals of PS nanocomposites established, the approach was applied to selected experiments to prove its validity. In general it was observed that the elastic modulus values calculated from the PS response were similar to that observed from macroscale strain measurements such as a strain gage. When simple damage models were applied to monitor the elastic modulus, it was observed that the rate of decay for the elastic modulus was much higher for the PS measurements than for the strain gage. A novel experiment including high resolution PS maps with secondary strain maps from digital image correlation is reviewed on an open hole tension, composite coupon. The two complementary measurements allow for a unique PS response for every location around the hole with a spatial resolution of 400 microns. Progression of intermediate damage mechanisms was observed before digital image correlation indicated them. Using the PS nanocomposite model, elastic modulus values were calculated. Introducing an elastic degradation model with some plastic deformation allows for estimation of material properties during the progression of failure. This work is part of a continuing effort to understand the mechanics of a stress sensing PS coating. The mechanics were then applied to various experimental data that provided elastic property calculations with high resolution. The significance is in the experimental capture of stress transfer in particulate composites. These findings pave the way for the development of high resolution stress-sensing coatings

Forbidden Waters

Since 1950 Yellowstone National Park has stood as the largest river system with a complete ban on boating in the world. Despite the prohibition, generations of kayakers have been unable to resist the world-class whitewater of the Black Canyon of the Yellowstone River, and today advocates on both sides of the issue press the Park Service to determine if visitors will ever legally wet a paddle on the thousands of miles of rivers and streams in the first National Park

Enhancing Cnt-composites With Raman Spectroscopy

Carbon Nanotubes (CNTs) have been the subject of intense research for their potential to improve a variety of material properties when developed as nano-composites. This research aims to address the challenges that limit the ability to transfer the outstanding nano-scale properties of CNTs to bulk nano-composites through Raman characterization. These studies relate the vibrational modes to microstructural characterization of CNT composites including stress, interface behavior, and defects. The formulation of a new fitting procedure using the pseudo-Voigt function is presented and shown to minimize the uncertainty of characteristics within the Raman G and D doublet. Methods for optimization of manufacturing processes using the Raman characterization are presented for selected applications in a polymer multiwalled nanotube (MWNT) composite and laser-sintered ceramic-MWNT composite. In the first application, the evolution of the MWNT microstructure throughout a functionalization and processing of the polymerMWNT composite was monitored using the G peak position and D/G intensity ratio. Processing parameters for laser sintering of the ceramic-MWNT composites were optimized by obtaining maximum downshift in stress sensitive G-band peak position, while keeping disorder sensitive D/G integrated intensity ratio to a minimum. Advanced Raman techniques, utilizing multiple wavelengths, were used to show that higher excitation energies are less sensitive to double resonance Raman effects. This reduces their influence and allows the microstructural strain in CNT composites to be probed more accurately. iii The use of these techniques could be applied to optimize any processing parameters in the manufacturing of CNT composites to achieve enhanced properties

The peripheral distribution and central projections of the sensory rami of the facial nerve in goldfish, Carassius auratus

Taste buds in goldfish and other cyprinids are found not only within the oropharyngeal cavity but also scattered over the external body surface. The external taste buds are innervated by branches of the facial nerve that terminate centrally in an enlargement of the medulla termed the facial lobe. The peripheral distribution and areas of innervation of the rami of the facial sensory nerve were determined by using a modification of the Sihler technique and by examination of a Bodian-stained head series. The central projections of individual rami of the facial sensory nerve were traced by means of the horseradish peroxidase (HRP) technique. Fibers of the facial sensory nerve distribute over the head and trunk via nine rami. The supraorbital ramus distributes fibers to taste buds above the eye. The palatine, maxillary, and mandibular rami innervate taste buds of the rostral palate, upper lip, and lower lip, respectively. The three rami of the hyomandibular trunk innervate taste buds on the operculum, branchiostegal rays, and in the lower cheek region. A facial recurrent ramus was also found that distributes fibers to taste buds on the trunk and pectoral fin via two rami, the lateral recurrent ramus and pectoral recurrent ramus. The facial sensory rami map somatotopically on the facial lobe. Overall, the projections follow an anteroposterior orientation with the long axis of the body tilted slightly ventrally. The lips and rostral palate make up a disproportionately large portion of the map, taking up nearly the entire ventral extent of the lobe. The trunk and pectoral fin regions map broadly across the dorsal portion of the lobe. Further, projections to the nucleus of the descending trigeminal tract were observed with labeling of the supraorbital, maxillary, and mandibular rami, and the rami of the hyomandibular trunk. Projections to the facial motor nucleus were also observed with labeling of maxillary and mandibular rami, perhaps indicating a monosynaptic reflex arc. These projections have not been reported in previous studies on the teleostean facial taste system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50035/1/902590306_ftp.pd

Stress and structural damage sensing piezospectroscopic coatings validated with digital image correlation

The piezospectroscopic effect, relating a material\u27s stress state and spectral signature, has recently demonstrated tailorable sensitivity when the photo-luminescent alpha alumina is distributed in nanoparticulate form within a matrix. Here, the stress-sensing behavior of an alumina-epoxy nanoparticle coating, applied to a composite substrate in an open hole tension configuration, is validated with the biaxial strain field concurrently determined through digital image correlation. The coating achieved early detection of composite failure initiation at 77% failure load, and subsequently tracked stress distribution in the immediate vicinity of the crack as it progressed, demonstrating non-invasive stress and damage detection with multi-scale spatial resolution

Bostonia: The Boston University Alumni Magazine. Volume 32

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Clinical and anatomical approach using Sihler's staining technique (whole mount nerve stain)

Sihler's staining allows visualization of the nerve distribution within soft tissues without extensive dissection and does not require slide preparation, unlike traditional approaches. This technique can be applied to the mucosa, muscle, and organs that contain myelinated nerve fibers. In particular, Sihler's technique may be considered the best tool for observing nerve distribution within skeletal muscles. The intramuscular distribution pattern of nerves is difficult to observe through manual manipulation due to the gradual tapering of nerves toward the terminal end of muscles, so it should be accompanied by histological studies to establish the finer branches therein. This method provides useful information not only for anatomists but also for physiologists and clinicians. Advanced knowledge of the nerve distribution patterns will be useful for developing guidelines for clinicians who perform operations such as muscle resection, tendon transplantation, and botulinum toxin injection. Furthermore, it is a useful technique to develop neurosurgical techniques and perform electrophysiological experiments. In this review, Sihler's staining technique is described in detail, covering its history, staining protocol, advantages, disadvantages, and possible applications. The application of this technique for determining the arterial distribution pattern is also described additionally in this study