Nondestructive Evaluation (NDE) Techniques Assessment for Graphite/Epoxy (Gr/Ep) Composite Overwrapped Pressure Vessels

The Westinghouse Science and Technology Center has undertaken a program to develop nondestructive evaluation (NDE) techniques for characterizing the internal structure of SiC particle-reinforced aluminum matrix composites at critical stages during fabrication [1–5]. Because of the large number of processing variables in the manufacture of metal matrix composites (MMC), the likelihood of having detrimental discontinuities is high. The detection of potential defects early in the processing cycle would increase the overall system yield, lower costs, and enhance final product quality [4]. The aim of this investigation was to develop and conduct NDE at various stages of MMC fabrication, correlate the results with microstructural characterization, and establish qualified product quality assurance processes. A large-scale billet was fabricated specially using powder metallurgy techniques to facilitate this objective. The billet contained implanted silicon-carbide particle and aluminum powder clusters as inspection targets. The billet was subsequently extruded into a primary cylindrical extrusion, and finally into a flat plate. The NDE objectives included evaluating the detectability and mapping the implanted defects through each of the processing steps. Comprehensive evaluation of MMC structures requires the use of multiple NDE techniques, including ultrasonic, eddy current, and radiographic testing. This paper concentrates on the results of the ultrasonic investigations. Our experimental approach was: (1) fabricate a MMC billet with intentionally placed inhomogeneities; (2) develop and implement NDE techniques to characterize the MMC internal structure; (3) extend the NDE techniques to intermediate processing and final product forms; and (4) correlate the NDE data with microstructural characterization and mechanical testing results.

Chapter 10 - Structural health monitoring and nondestructive evaluation applications of the stress, vibration, and wave analysis in aerospace composites

The increased use of composite overwrapped pressure vessels (COPVs) in space and commercial applications, and the explosive nature of pressure vessel ruptures, make it crucial to develop techniques for early condition based damage detection. The need for a robust health monitoring system for COPVs is a high priority since the mechanisms of stress rupture are not fully understood. Embedded Fiber Bragg Grating (FBG) sensors have been proposed as a potential solution that may be utilized to anticipate and potentially avoid catastrophic failures. The small size and light weight of optical fibers enable manufactures to integrate FBGs directly into composite structures for the purpose of structural health monitoring. A challenging aspect of embedding FBGs within composite structures is the risk of potentially impinging the optical fiber while the structure is under load, thus distorting the optical information to be transferred. As the COPV is pressurized, an embedded optical sensor is compressed between the expansion of the inner bottle, and the outer overwrap layer of composite. In this study, FBGs are installed on the outer surface of a COPV bottle as well as embedded underneath a composite overwrap layer for comparison of strain measurements. Experimental data is collected from optical fibers containing multiple FBGs during incremental pressurization cycles, ranging from 0 to 10,000 psi. The graphical representations of high density strain maps provide a more efficient process of monitoring structural integrity. Preliminary results capture the complex distribution of strain, while furthering the understanding of the failure mechanisms of COPVs.

Evaluation of Fuel-Clad Chemical Interaction in PFBR MOX test fuel pins

Non-destructive evaluation (NDE) techniques are essential to detect damage in structures, including airplanes, and require further improvement. Extant NDE techniques are often time-consuming, and their spatial resolution and in situ capabilities are limited. In this paper, a new NDE technique is demonstrated using the Joule heating effect of carbon nanotube (CNT) networks embedded within structural composites (also known as nanoengineered composites). Via local resistive heating, damage in the composite causes increased electrical and thermal resistance that is visualized with standard thermographic imaging. Multiple improved characteristics have been experimentally confirmed, including real-time measurement, high resolution (~0.1 mm), and simple and low-power (15 o C rise at 1 W) operation. Furthermore, the ability to detect barely visible (and internal) damage, and an additional de-icing functionality, are presented. This materials-based sensing technique offers a novel and practical approach for in situ structural health monitoring to prevent structural failures.

A study of residual burst strength of composite over wrapped pressure vessel due to low velocity impact

The Naval Research Laboratory (NRL) has developed a new bipropellant Upper Stage providing orbit transfer propulsion capabilities from a Delta II launch vehicle. This bipropellant stage utilizes a pair of Composite Overwrapped Pressure Vessels (COPV) to store helium for pressurization of the Upper Stage fuel and oxidizer propellant tanks. A systems engineering trade study was performed to determine the size requirements of the helium tanks followed by competitive vendor selection and subsequent tank development and qualification program. This paper discusses the helium tank sizing analysis and documents details of the COPV design and qualification testing effort. Additionally, spacecraft installation interfaces, a tank pressure hazard analysis, and on-orbit temperature and pressure performance are summarized and presented. Program description. The Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and Marine Corps and conducts a broad program of scientific research, technology and advanced development. The NRL, sponsored by the Defense Advanced Research Projects Agency (DARPA), developed the Upper Stage (US) for the Microsatellite Technology Experiment (MiTEx) program by drawing on its corporate experience building and operating spacecraft. The Upper Stage provided the orbit transfer propulsion for the MiTEx microsatellites and was launched on a Delta II in June of 2006. NRL personnel performed a series of mission analyses and trade studies that showed that an earth storable liquid bipropellant system would best satisfy the MiTEx orbital maneuvering requirements. A constant feed pressure is required to optimize bipropellant engine performance; therefore the propulsion subsystem design includes two Composite Overwrapped Pressure Vessels (COPV) to store helium pressurant. ARDE, Inc was selected as the COPV contractor after a competitive procurement. ARDE developed a tank design to meet the NRL requirements, and conducted extensive tests both to qualify the design and to provide thermal – helium expulsion data to support NRL mission planning needs. Mission sizing and blowdown. NRL personnel performed a series of analyses to support the COPV procurement. These included parametric studies, mission requirements flowdown, budget allocations to the various components including the COPV, and packaging studies. The key requirement addressed in these analyses was the pressure remaining in the COPV at the end of each maneuver and 1 Osborn, Clauss, Gorin, Netwall, “Micro-satellite Technology Experiment (MiTEx) Upper Stage Propulsion System Development,” AIAA 2007-5434 how well that pressure could satisfy feed system flow requirements. These analyses considered the propellant tank volume, the propellant volume required for various orbital maneuvers, the propellant volumetric flow rate, and the COPV’s operating pressure at the beginning of the maneuver to develop a trade-space that included helium end of maneuver pressure and helium flow path pressure drop. The parametric analyses showed that the temperature of the helium at the end of the maneuver is the driver for the final expected pressure. The helium tank blowdown can be modeled as a polytropic process using Equation 1 where n represents a constant for a particular process.

A novel damage localization technique for type III composite pressure vessels based on guided wave mode-matching method

In this work the effectiveness of the one-dimensional (1D) electrical resistance method at sensing low velocity impact damage in AS4/3501-6 carbon fiber polymer matrix laminated composite plate specimens was studied. A fully instrumented experimental setup for characterization of electrical properties has been developed. Two types of laminates were tested: a 16-ply orthotropic [0/45/-45/90]2s laminate (thickness = 2.25 mm) and a 32-ply orthotropic [0/45/-45/90]4s laminate (thickness = 4.5 mm). Single impact and cumulative damage studies were conducted for both the 16- and 32-ply samples. Before and after each impact, the top surface resistance and the oblique resistance (resistance through the thickness of the specimen at an oblique angle) of the impact region were measured and their effectiveness to sense damage was evaluated. I. Introduction Fiber reinforced composite materials are known to be susceptible to low velocity impact damage, which represents a serious design concern for composite structures. Particularly precarious situations arise when no apparent damage at the impacted surface of the composite structure is accompanied by a significant reduction in structure’s strength and stiffness. As current and future aerospace systems rely more and more on fiberreinforced polymer composites, damage detection becomes increasingly important and non-destructive evaluation methods are still highly desirable for such composites. At the same time, adding damage sensing functionality to composites represents an attractive alternative, where a composite material itself may serve as a damage sensor. Carbon fiber polymer matrix composites are electrically conductive. The conductive carbon fibers constitute a conductive network that allows the composite as a whole to be conductive, even though the polymer matrix material is non-conductive. The overall electrical properties of the composites depend not only on the inherent electrical properties of the carbon fibers and their volume fraction in the composite, but also on the connectivity of fibers in composites, sequence of plies, etc. When impact damage occurs, the connectivity of fibers in the individual plies and at the ply interfaces changes, which results in the overall changes in the electrical properties and particularly in the electrical resistance. Therefore, since the conductivity of a CFRP laminate changes with damage, measuring the electrical conductivity of such a composite provides a means of damage sensing. There have been a number of studies on the electrical characterization of carbon fiber polymer matrix composites conducted in the past [1-8] that attempted to monitor changes in the electric resistance and electric field that occur as a result of mechanical damage. Two main techniques have been employed to sense impact

Defect identification in GRID-LOCK ® joints

Width effect on the modulus of elasticity of hardwood lumber measured by non-destructive evaluation techniques

Nondestructive evaluation (NDE) techniques are used in many industries to evaluate the properties of components and inspect for flaws and anomalies in structures without altering the part’s integrity or causing damage to the component being tested. This includes monitoring materials’ condition (Material State Awareness (MSA)) and health of structures (Structural Health Monitoring (SHM)). NDE techniques are highly valuable tools to help prevent potential losses and hazards arising from the failure of a component while saving time and cost by not compromising its future usage. On the other hand, Artificial Intelligence (AI) and Machine Learning (ML) techniques are useful tools which can help automating data collection and analyses, providing new insights, and potentially improving detection performance in a quick and low effort manner with great cost savings. This paper presents a survey on state of the art AI-ML techniques for NDE and the application of related smart technologies including Machine Vision (MV) and Digital Twins in NDE.

Compared with conventional non-destructive evaluation (NDE) techniques, such as radiography, ultrasound, magnetic particle inspection and eddy current, the coplanar capacitive sensing technique is a newly emerging technique with promising future prospects. Aiming to show the capabilities of coplanar capacitive sensors (CCSs) for NDE, this review paper exploits existing literature on the subject to provide a general systematic overview of the capacitive NDE technique using CCSs. This review focuses on the fundamentals of the technique, factors affecting sensor performance, existing designs of CCSs used for defect detection and finally, the different applications of CCSs for defect detection in different fields of NDE. The existing challenges and future prospects of the CCS technique are also discussed. Amidst the prevalent challenges, obtaining better performance from CCSs has been mostly done by using different geometric designs, but less emphasis has been put on optimising circuit design and choice of sensor component materials. The key to optimisation of sensor performance is rooted in establishing a balance among trade-offs. The various advantages of the technique, compared to conventional NDE techniques, allow for different applications and attest to the potential of the technique for new applications in the future.

Eddy current testing (ECT) is one of the most important techniques in nondestructive evaluation. A higher probe sensitivity is always pursued in ECT. To improve the probe sensitivity, the near electrical resonance signal enhancement (NERSE) technique was recently proposed. In the NERSE technique, a coaxial cable connecting with the probe coil is introduced to provide a capacitance for the electrical resonance. However, the long coaxial cable is awkward and inconvenient in engineering applications, restraining the usability of such probes. Metamaterials (MTMs) are novel artificial electromagnetic media and have been proved to be effective in manipulating the impedance of a solenoid coil. In other words, in principle, MTMs can be used in the same way as that a coaxial cable in NERSE in ECT. Based on this argument, low-frequency magnetic MTMs are introduced as the probe cores to provide a new approach to achieve the electrical resonance for the NERSE technique. A promising feature of the proposed approach is that the detecting signals and sensitivity are significantly increased due to the extraordinary electromagnetic properties of the MTM. The most salient features of an MTM core over a ferrite core are: 1) effective permeability of the MTM core will vary sharply from a high positive to a high negative values when crossing the resonance frequency, resulting in not only a high magnetic flux density in the tested material but also an extremely large variation of the normalized impedance which is very essential in identifying a crack and 2) electromagnetic properties of an MTM will increase with the increase of frequency, whereas those of a ferrite material usually degrade sharply with the increase of frequency. To demonstrate the advantages of the proposed new probe, comprehensive numerical and experimental studies are conducted, and the results have shown the high performance of the proposed probe. In addition, the proposed MTM-core probe also exhibits a diverse versatility and convenience in engineering applications as compared with the existing NERSE technique.

As the requirements on the accuracy of nondestructive testing and evaluation are increasing, multiple nondestructive evaluation (NDE) methods are often employed to increase the reliability and reduce the uncertainty of the testing and evaluation. The need to process and analyze data from multiple sources uses the technique named data fusion, which has been growing rapidly in the NDE community in recent years. This paper reviews the progress in NDE data fusion techniques and examines the mathematical fusion algorithms, which include but are not limited to optimization methods, multiresolution approaches, heuristic methods, probabilistic methods, and scientific visualization. In the light of recent applications in NDE data fusion, important issues in handling the acquired data and applying the fusion algorithms are identified and discussed. A generic framework to apply the NDE data fusion process is described. The study on fusion of advanced NDE and sensor techniques opens up prospects for the diagnostic and prognostic health monitoring applications in the future.