Acellent Technologies (United States)

Space structures are one of the most critical components for any spacecraft, as they must provide the maximum amount of livable volume with the minimum amount of mass. Inflatable, deployable structures in particular, have been investigated by NASA since the early 1950’s and used in a number of spaceflight applications. Inflatable habitats, airlocks, and space stations can be used for in-space living spaces and surface exploration missions. Inflatable structures are being pursued as candidates for long-term habitats in space and on the surfaces of the Moon and Mars. Many concepts by the NASA and industry utilize high-strength, low-weight softgoods materials, such as Vectran, as the primary load-bearing structure in inflatable habitats. The ability to monitor and assess the structural health of an inflatable module is an important factor in determining the feasibility of using inflatable technologies for habitat requirements, especially in the presence of micrometeoroid and orbital debris (MMOD) threats. There is therefore a need for Structural Health Monitoring (SHM) methods to perform detection, localization, and quantification of damage to structural layers throughout the structure’s mission. This capability must be accomplished within real constraints for sensor volume, mass, and crew resources, including being able to perform effective damage monitoring of the inflatable habitat layers from the interior during a mission either on a routine basis or as a quickresponse basis. This paper discusses the development of an approach for SHM for inflatable softgoods, and testing a laboratory proof of concept of the preliminary design, which integrates the SHM approach into inflatable habitat test articles. An experimental test setup for performing the initial feasibility demonstration for impact detection using SMART Layer sensors. An initial test setup for testing was developed and testing performed for impact detection.

This contribution presents a novel strategy to achieve real-time prediction of non-penetrating impact-induced damage, especially delamination between plies of composite laminated structures. The proposed strategy aims to create an optimum-sized database of simulated damage information on a given laminated structure using numerical failure models and pattern recognition technique. A multi-stage data clustering algorithm is implemented to identify regions in the structural Finite Element (FE) model that have similar damage signatures. The generated database is linked to the real-time estimate of impact location and load-time history obtained from piezoelectric transducers based passive impact monitoring system. A composite stiffener panel is selected as a model problem and it is shown that the proposed strategy based on pattern recognition will result in large savings in computational cost for the database generation besides providing real-time damage diagnostic capabilities for in-service adverse impact events within certain confidence bounds.

Structural rehabilitation with carbon fiber reinforced composite materials has proven to bean excellent way to enhance/repair steel reinforced concrete structures and prolongtheir service lives. However, disbonds between composite repair patches and hoststructures continue to be a great concern of this technology. In this paper, a built-inpiezoelectric sensor network based structural health monitoring system is introduced formonitoring the disbonds between composite repair patches and the host structures.This diagnostic system combines the sensor network, diagnostic hardware anddata analysis software allowing for real-time monitoring of the integrity of thebonded repair. The effectiveness of detecting disbonds using the system has beendemonstrated on a full scale bridge model in a laboratory setting. The bridge model wasloaded incrementally to failure, and disbond monitoring was carried out during theloading intervals. Test results showed that the system could detect the disbondsbefore they have a noticeable effect on the global stiffness of the bridge model.

Structural Health Monitoring (SHM) that uses integrated sensor network to provide real-time monitoring of in-service structures can improve the safety and reliability of the structures significantly. Acellent Technologies' SHM systems based on SMART technology consists of the integrated sensor network, diagnosis hardware platform and the diagnosis software. This paper introduces the latest SMART damage detection hardware platform - ScanGenie and the new analysis software for damage detection in composite and metal structures. The ScanGenie is a portable high-performance hardware that provides many features such as through-transmission, pulse-echo, temperature measurement, self-diagnosis, sensor diagnosis, etc. The new analysis software is based on the ScanGenie hardware to provide functions such as temperature compensation, auto-gain adjustment, impedance-based diagnosis and probability of detection. The system can be used for damage detection in most composite and metal structures such as aircraft, spacecraft and civil infrastructures.

Piezoelectric transducers and fiber-optic sensors have been established as excellent sensors for monitoring structural health. To utilize the advantages of both piezoelectric transducer (PZT) and fiber-optic sensor, hybrid piezoelectric/fiber-optic structural health monitoring systems have been developed for quick nondestructive evaluation and long-term health monitoring of aerospace vehicles and civil structures. In this article, a general review of the state of art of the hybrid piezoelectric/fiber-optic sensing techniques is presented, which include the ultrasonic stress wave detectability study based on both experimental demonstration and theoretical analysis. An integrated hybrid active system and its application are also introduced. The hybrid active system uses PZT transducers as actuators to input diagnostic waveforms to the structure, and fiber Bragg grating (FBG) sensors to receive the response signals in a pitch-catch manner. Demonstrations of damage detection of the system in both metallic and composite structures with the proposed system are presented as well. Keywords: structural health monitoring; hybrid system; piezoelectric transducer; fiber Bragg grating; damage detection; fiber-optic sensor

The United States is striving to develop an Operationally Responsive Space capability. The goal is to be able to deliver tailored spacecraft capabilities to the warfighter as needs arise. This places a premium on the timespan between generating that requirement and having a functioning satellite performing its mission on orbit. Although there is lively debate regarding how to achieve this responsive space capability, one thing remains undeniable; the satellite flight qualification and launch vehicle integration process needs to be dramatically truncated. This paper describes the Air Force Research Laboratory's attempts to validate the use of Structural Health Monitoring (SHM) in lieu of traditional structural flight qualification testing schemes (static and shock loads, random vibration, coupled loads analysis, thermal vacuum testing, etc.) for potential Responsive Space (RS) satellites.

Gelcasting is a promising new technology for manufactur‐ing advanced structural ceramic components. The process involves drying of the “green” gelcast part before densifi‐cation. The physical mechanisms that control this relatively long drying process are not well understood. In this study, several controlled experiments have been performed to elu‐cidate the key mechanisms. A one‐dimensional drying model has been formulated, based on evaporation and gas‐eous diffusion through the part. Experimental data have been used to obtain correlations for model parameters. This model predicts the instantaneous moisture content of a gelcast sample with an accuracy of better than 10% when the dryer humidity, dryer temperature, and sample thick‐ness are specified.

Larger lesions were created when the electrode of an RF ablation system was actively cooled below blood temperature. To keep the maximal tissue temperature at about 90/spl deg/C, significantly more RF power had to be delivered. Because the hottest tissue region moved farther from the electrode surface, it was more difficult to predict the adequate tissue heating. Therefore, the probability of overheating the tissue and producing micro-explosions increased.

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.