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Mechanical Engineering Commons

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1983

Polymer and Organic Materials

Articles 1 - 6 of 6

Full-Text Articles in Mechanical Engineering

Fiber Optics For A Damage Assessment System For Fiber Reinforced Plastic Composite Structures, Roger M. Crane, Aleksander B. Macander, James Gagorik Jan 1983

Fiber Optics For A Damage Assessment System For Fiber Reinforced Plastic Composite Structures, Roger M. Crane, Aleksander B. Macander, James Gagorik

Review of Progress in Quantitative Nondestructive Evaluation

There are a limited number of nondestructive evaluation techniques available for field inspection of large composite structures and practically no viable techniques for in-service inspection. With this in mind, an innovative Damage Assessment System is proposed which is based on a concept of using an optical fiber mesh, implanted into the body of a fiber reinforced composite structure. Such a mesh would become an integral part of the structure during the course of its fabrication. The selection of the mesh fibers would be predicated on their strain to failure characteristics and strain compatibility with the base, composite reinforcing fibers. This ...


Cure Monitoring Of Thermosetting Polymers By An Ultrasonic Technique, Donald L. Hunston Jan 1983

Cure Monitoring Of Thermosetting Polymers By An Ultrasonic Technique, Donald L. Hunston

Review of Progress in Quantitative Nondestructive Evaluation

In the fabrication of components with thermosetting polymers, an essential step is the proper optimization of the cure cycle. In the early phases of the cure the polymer must have the appropriate flow properties to assure the proper wetting, spreading, and forming. It must then harden without excessive build up of residual stresses and flaws or the loss of adhesion at any interfaces that are present. To complicate the situation further, many applications such as composites, adhesives, paints, and protective coatings involve thin films whose cure behavior is significantly different than that for bulk samples. To help address this problem ...


Ultrasonic Signal Processing For Multilayered Nde, Ramesh Shankar, Stephen S. Lane, Jeffrey M. Warren Jan 1983

Ultrasonic Signal Processing For Multilayered Nde, Ramesh Shankar, Stephen S. Lane, Jeffrey M. Warren

Review of Progress in Quantitative Nondestructive Evaluation

The interpretation of ultrasonic signals in the inspection for flaws in bonded regions of multilayered specimens is difficult because of signal energy loss due to material attenuation, undesired reverberations within certain layers, and overlapping responses from different interfaces because of finite transducer bandwidth. The flaws are usually air gaps, lack of adhesion, and porosity within the bonding agent.

While ultrasonic NDE signal interpretation can always be improved with appropriate instrumentation — broader bandwidth transducers for increased resolution, for example — signal processing allows for further enhancement using a digital computer. Material attenuation can be compensated for by using digital filters that preferentially ...


Interferometric Techniques Using Embedded Optical Fibers For The Quantitative Nde Of Composites, Janet C. Wade, Richard O. Claus Jan 1983

Interferometric Techniques Using Embedded Optical Fibers For The Quantitative Nde Of Composites, Janet C. Wade, Richard O. Claus

Review of Progress in Quantitative Nondestructive Evaluation

Optical interferometric techniques using single mode optical fiber waveguide embedded in composites and other layered materials have been used to measure one- and two-dimensional stress distributions and acoustic emission caused by applied point source loads. By interferometrically comparing the phases of coherent optical signals propagated through an embedded sample fiber and a bypass reference fiber, a signal proportional to the instantaneous strain integrated along the embedded length of the sample fiber has been detected. System calibration has been obtained by applying a one-dimensional dc strain field to a cantilever beam containing the fiber. Using this calibrated system, an array of ...


A Computerized Ultrasonic Scanning Bridge For Defect Imaging: Composite Materials, Donald Boyd, William Mcdonald, Andrew Simmons Jan 1983

A Computerized Ultrasonic Scanning Bridge For Defect Imaging: Composite Materials, Donald Boyd, William Mcdonald, Andrew Simmons

Review of Progress in Quantitative Nondestructive Evaluation

A computerized ultrasonic scanning bridge has been developed for the scanning and imaging of defects in structures. The raster scaning pattern can be implemented with any pair of the six available axes. The digitized ultrasonic signal can be imaged using a Peritek Graphic system. Details of the ultrasonic scanning bridge and imaging system will be reviewed.

Examples of the evaluation of a graphite epoxy component will be reviewed. The scanning of the composite part requires the use of the two angulation axis for the raster scanning. The correlation of the ultrasonic inspection with failure pressure of the graphite epoxy component ...


Development Of An Acoustic Model For Multilayered Nde, Ramesh Shankar, Stephen S. Lane Jan 1983

Development Of An Acoustic Model For Multilayered Nde, Ramesh Shankar, Stephen S. Lane

Review of Progress in Quantitative Nondestructive Evaluation

A computer based acoustic model has been developed for the NDE of multilayered structures [1]. The model is applicable for normal or off-normal incident excitation, with receiver in pulse-echo, pitch-catch or in array mode. The model can simulate the observed signal for arbitrary frequency response of the transmitting and receiving transducer. In addition, the model considers attenuation and mode conversion effects in each layer in predicting the ultrasonic response.

While earlier works [2,3,4] considered normal incidence and non attenuative media, the current model’s capabilities have been expanded to include off-normal incident angles and the attendant mode conversions ...