| Thin Film Acoustic Devices for In-Situ Monitoring of Composite Processes |
OCT 94 |
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| Authors:
Nisar Shaikh
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 | The objective of this work was to develop non-invasive sensors and related technique for in-situ cure monitoring of composite materials. Unlike the conventional acoustic sensors these sensors need not be inserted in the parts being monitored, eliminating degradation of the material. Instead these sensors are surface mounted so they hug the part being monitored and are designed so that they can be conveniently housed in the tool. Two different type ... |
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| Stress Measurement in Structural Plastics by L-cr Waves |
94 |
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| Authors:
Nisar Shaikh
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| Longitudinal waves at the critical incidence (L-cr) angle have been utilized to measure residual stress in glass and plastics used for high performance aircraft. The acoustoelastic effect is most pronounced in this mode. The novel feature of this research is the development of transducers and technique that are patterned after acoustic microscopy. However, the reflected specular and leaky wave signals are received by separate ceramics, allowing elaborate signal processing. Unlike ... |
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| Smart Structural Composites with Piezoelectric Micro-Constituents |
DEC 92 |
16 pages |
| Authors:
Nisar Shaikh; NEBRASKA UNIV LINCOLN DEPT OF MECHANICAL ENGINEERING
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 | The research culminated into the feasibility of smart structural composite materials, in which the microstructure is modified with the introduction of a piezoelectric constituent. Greater success was achieved in the sensing aspect of smart properties, enabling the material to have an inherent property of health monitoring. By sensing and quantifying elastic strain, the material can monitor its dynamic state (vibration), degradation and damage. In actuation, the material is readily suitable ... |
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| Transducers and Technique for Ultrasonic Nondestructive Evaluation of Structural Plastics |
92 |
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| Authors:
Nisar Shaikh
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| Plastics like acrylics and polycarbonates are important structural materials for transparent enclosures in high performance aircraft. The ultrasonic nondestructive techniques widely used for metals should also be effective for these plastics. There are, however, two major problems encountered in dealing with plastics. First, because acoustic velocities are lower in plastics, it is difficult to launch Rayleigh and Lamb waves with standard wedges and immersion transducers. Second, the viscoelastic nature of ... |
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| Surface Acoustic Wave Technique for Craze Detection and Stress Measurement of Aircraft Transparencies |
FEB 91 |
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| Authors:
Nisar Shaikh; ANALYTIC ENGINEERING CO LINCOLN NE
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| A nondestructive testing technique that employs surface acoustic waves was developed for detecting and characterizing flaws and degradation in transparent enclosures of fighter aircraft. The focus of research has been acoustic measurement of craze and stresses (i.e. residual stress) in the acrylic top layer of laminated transparencies. The craze severely degrades the optical performance of the transparent enclosure and is one of the major causes of the limited service life. ... |
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