Structural Health Monitoring of Large Structures Using Acoustic Emission-Case Histories

Acoustic emission (AE) techniques have successfully been used for assuring the structural integrity of large rocket motorcases since 1963 [...

Advanced radar absorbing ceramic-based materials for multifunctional applications in space environment

In this review, some results of the experimental activity carried out by the authors on advanced composite materials for space applications are reported. Composites are widely employed in the aerospace industry thanks to their lightweight and advanced thermo-mechanical and electrical properties. A critical issue to tackle using engineered materials for space activities is providing two or more specific functionalities by means of single items/components. In this scenario, carbon-based composites are believed to be ideal candidates for the forthcoming development of aerospace research and space missions, since a widespread variety of multi-functional structures are allowed by employing these materials. The research results described here suggest that hybrid ceramic/polymeric structures could be employed as spacecraft-specific subsystems in order to ensure extreme temperature withstanding and electromagnetic shielding behavior simultaneously. The morphological and thermo-mechanical analysis of carbon/carbon (C/C) three-dimensional (3D) shell prototypes is reported; then, the microwave characterization of multilayered carbon-filled micro-/nano-composite panels is described. Finally, the possibility of combining the C/C bulk with a carbon-reinforced skin in a synergic arrangement is discussed, with the aid of numerical and experimental analyses

Technology for large space systems: A special bibliography with indexes (supplement 03)

A bibliography containing 217 abstracts addressing the technology for large space systems is presented. State of the art and advanced concepts concerning interactive analysis and design, structural concepts, control systems, electronics, advanced materials, assembly concepts, propulsion, solar power satellite systems, and flight experiments are represented

Electromagnetic Interference Shielding Effectiveness of Interlayered Systems Containing Metal-Oxide, Conducting Polymer and Carbon Nanotube Reinforced Polymeric Composites

The Electromagnetic Interference (EMI) Shielding Effectiveness (SE) has become one of the important requirements for the devices associated with telecommunication systems consisting of large frequency bands. The degradation of the quality of transmitting signal influenced by frequencies emitting from external sources can be reduced by covering the circuits of the devices by EMI Shielding materials like polymer composites, metal-based nanofiber mats, the metal of oxide films, etc. The investigation strives for the attenuation of EMI by introducing two composite mats from conducting polymer-based, multiwalled carbon nanotubes (MWCNTs) coated Nylon 6 nanofiber composites. Two other composite mats are also developed by the Forcespinning® method using sol solution of functionalized multiwalled carbon nanotubes (f-MWCNTs) and magnetite (Fe3O4) into as-prepared polyacrylonitrile (PAN) which is then carbonized at elevated temperature to convert it into carbon nanofiber (CNF). A total of four layers of mats are stacked and compression molded together to develop one multilayered composite (MLC 1). The Fe3O4 has higher magnetic properties which may provide a good magnetic loss effect. The focus is to investigate the synergistic effects between higher magnetic Fe3O4, conductive MWCNTs nanofillers with the dielectric CNF, conducting polymer, and functionalized MWCNTs coated nanofiber composite which can provide information about the dominating mechanism. (Absorption, reflection, or multiple reflections) for EMI SE. The multilayered composite (MLC 2) consisting 8 layers (repeating the stacking sequence again) has given the highest obtained value more than 40 dB EMI SE in the frequency range from 300–500 MHz. The results will bring some findings of optimized materials yielding good EMI SE in lightweight applications

Wireless Sensors and Actuators for Structural Health Monitoring of Fiber Composite Materials

This work evaluates and investigates the wireless generation and detection of Lamb-waves on fiber-reinforced materials using surface applied or embedded piezo elements. The general target is to achieve wireless systems or sensor networks for Structural Health Monitoring (SHM), a type of Non-Destructive-Evaluation (NDE). In this sense, a fully wireless measurement system that achieves power transmission implementing inductive coils is reported. This system allows a reduction of total system weight as well as better integration in the structure. A great concern is the characteristics of the material, in which the system is integrated, because the properties can have a direct impact on the strength of the magnetic field. Carbon-Fiber-Reinforced-Polymer (CFRP) is known to behave as an electrical conductor, shielding radio waves with increasing worse effects at higher frequencies. Due to the need of high power and voltage, interest is raised to evaluate the operation of piezo as actuators at the lower frequency ranges. To this end, actuating occurs at the International Scientific and Medical (ISM) band of 125 kHz or low-frequency (LF) range. The feasibility of such system is evaluated extensively in this work. Direct excitation, is done by combining the actuator bonded to the surface or embedded in the material with an inductive LF coil and setting the circuit in resonance. A more controlled possibility, also explored, is the use of electronics to generate a Hanning-windowed-sine to excite the PWAS in a narrow spectrum. In this case, only wireless power is transmitted to the actuator node, and this lastly implements a Piezo-driver to independently excite Lamb-waves. Sensing and data transfer, on the other hand, is done using the high-frequency (HF) 13.56 MHz. The HF range covers the requirements of faster sampling rate and lower energy content. A re-tuning of the antenna coils is performed to obtain better transmission qualities when the system is implemented in CFRP. Several quasi-isotropic (QI) CFRP plates with sensor and actuator nodes were made to measure the quality of transmission and the necessary energy to stimulate the actuator-sensor system. In order to produce baselines, measurements are prepared from a healthy plate under specific temperature and humidity conditions. The signals are evaluated to verify the functionality in the presence of defects. The measurements demonstrate that it is possible to wirelessly generate Lamb-waves while early results show the feasibility to determine the presence of structural failure. For instance, progress has been achieved detecting the presence of a failure in the form of drilled holes introduced to the structure. This work shows a complete set of experimental results of different sensor/-actuator nodes

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

Aeronautical engineering: A special bibliography with indexes, supplement 82, April 1977

This bibliography lists 311 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1977

Damage identification in structural health monitoring: a brief review from its implementation to the Use of data-driven applications

The damage identification process provides relevant information about the current state of a structure under inspection, and it can be approached from two different points of view. The first approach uses data-driven algorithms, which are usually associated with the collection of data using sensors. Data are subsequently processed and analyzed. The second approach uses models to analyze information about the structure. In the latter case, the overall performance of the approach is associated with the accuracy of the model and the information that is used to define it. Although both approaches are widely used, data-driven algorithms are preferred in most cases because they afford the ability to analyze data acquired from sensors and to provide a real-time solution for decision making; however, these approaches involve high-performance processors due to the high computational cost. As a contribution to the researchers working with data-driven algorithms and applications, this work presents a brief review of data-driven algorithms for damage identification in structural health-monitoring applications. This review covers damage detection, localization, classification, extension, and prognosis, as well as the development of smart structures. The literature is systematically reviewed according to the natural steps of a structural health-monitoring system. This review also includes information on the types of sensors used as well as on the development of data-driven algorithms for damage identification.Peer ReviewedPostprint (published version