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The use of acoustic emission to characterize impact damage in composite structures is being performed on composite bottles wrapped with graphite epoxy and kevlar bottles. Further development of the acoustic emission methodology will include neural net analysis and/or other multivariate techniques to enhance the capability of the technique to identify dominant failure mechanisms during fracture. The acousto-ultrasonics technique will also continue to be investigated to determine its ability to predict regions prone to failure prior to the burst tests. Characterization of the stress wave factor before, and after impact damage will be useful for inspection purposes in manufacturing processes. The combination of the two methods will also allow for simple nondestructive tests capable of predicting the performance of a composite structure prior to its being placed in service and during service. Workman, Gary L. (Principal Investigator) and Walker, James L. Marshall Space Flight Center...
Finding and slzmg cracks and other crack-like discontinuities has been the center of attention for scientists and engineers developing and using nondestructive evaluation (NDE) technology. However, with advanced mate rials being "engineered" and used in critical structural components, a new for NDE has emerged. Whereas many traditional engineering materi challenge als fail due to the initiation and self-similar propagation of a crack, reinforced composite materials degrade and fail in a manner more analogously to the collapse of a structure. Consequently the NDE of such materials involves assessing the combined effect of the material's damaged condition rather than identifying and sizing single critical imperfection. In 1979 Alex Vary, seeking to address the challenge confronting the NDE of advanced fiber reinforced composite materials began work on a new method of materials characterization. Focusing on the problem of evaluating graphite fiber reinforcedl epoxy laminated plates; Vary used a piezoelectric transducer to excite a mechanical disturbance in a plate and, with a sensi tive piezoelectric transducer monitored the disturbance on the same surface of the plate. (Placing the transducers on the same surface was primarily for practical purpose but their displacement in the direction of anticipated service load was of fundamental significance!) To quantify this observation, he counted the number of excursions, of the resulting electrical signal, above a arbitrary voltage threshold; a procedure frequently used for acoustic emission signal analysis.
This open access book presents established methods of structural health monitoring (SHM) and discusses their technological merit in the current aerospace environment. While the aerospace industry aims for weight reduction to improve fuel efficiency, reduce environmental impact, and to decrease maintenance time and operating costs, aircraft structures are often designed and built heavier than required in order to accommodate unpredictable failure. A way to overcome this approach is the use of SHM systems to detect the presence of defects. This book covers all major contemporary aerospace-relevant SHM methods, from the basics of each method to the various defect types that SHM is required to detect to discussion of signal processing developments alongside considerations of aerospace safety requirements. It will be of interest to professionals in industry and academic researchers alike, as well as engineering students. This article/publication is based upon work from COST Action CA18203 (ODIN - http://odin-cost.com/), supported by COST (European Cooperation in Science and Technology). COST (European Cooperation in Science and Technology) is a funding agency for research and innovation networks. Our Actions help connect research initiatives across Europe and enable scientists to grow their ideas by sharing them with their peers. This boosts their research, career and innovation.
This open access book presents papers displayed in the 2nd International Conference on Energy and Sustainable Futures (ICESF 2020), co-organised by the University of Hertfordshire and the University Alliance DTA in Energy. The research included in this book covers a wide range of topics in the areas of energy and sustainability including: • ICT and control of energy;• conventional energy sources;• energy governance;• materials in energy research;• renewable energy; and• energy storage. The book offers a holistic view of topics related to energy and sustainability, making it of interest to experts in the field, from industry and academia.
“...a comprehensive and well written book, which...will be useful reading for both researchers entering the field and experienced specialists looking for new ideas....a valuable and long-lasting contribution to experimental mechanics.” – Stepan Lomov, KU Leuven This expert volume, an enhanced Habilitation thesis by the head of the Materials Testing Research Group at the University of Augsburg, provides detailed coverage of a range of inspection methods for insitu characterization of fiber-reinforced composites. The failure behavior of fiber reinforced composites is a complex evolution of microscopic damage phenomena. Beyond the use of classical testing methods, the ability to monitor the progression of damage insitu offers new ways to interpret the materials failure modes. Methods covered include digital image correlation, acoustic emission, electromagnetic emission, computed tomography, thermography, shearography, and promising method combinations. For each method, the discussion includes operational principles and practical applications for quality control as well as thoughtful assessment of the method's strengths and weakness so that the reader is equipped to decide which method or methods are most appropriate in a given situation. The book includes extensive appendices covering common experimental parameters influencing comparability of acoustic emission measurements; materials properties for modeling; and an overview of terms and abbreviations.