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Author: Sazid Irfan Ahmed Publisher: ISBN: Category : Electronic dissertations Languages : en Pages :
Book Description
Structural health monitoring of aerospace structures is becoming vital as lightweight composite materials are increasingly used in aero-structures. Composites have various types of failure modes, which make it even more important to identify fault or damage compared to isotropic materials. Therefore, on-site health monitoring is one of the most preferred methodologies for detecting internal crack or damage at its initial stage to enhance operating safety and reduce repair cost. Recently, piezoelectric transducers are on high demand for on-site health monitoring because of its high bandwidth sensitivity. They simultaneously perform as actuators and sensors and embedded in the structure for real time response indicative of the condition of the structure. Their characteristics show direct coupling between the electrical impedance and structural impedance. The electrical impedance or admittance changes according to modification in mass, stiffness or damping properties of the host body to which the transducer is attached. In this study, plain-weave textile composites are utilized to demonstrate the capability of piezoelectric transducer. The elastic properties of the composite are determined using the fiber tow properties that are derived via the Concentric Cylinder Assemblage micromechanics model. Finite element modeling is done in commercial software ANSYS APDL to observe electrical admittance variation around natural frequency of the entire structure to investigate structure condition. Delamination was studied at first but results show very small shift in frequency of the same mode number for healthy and defective structures along with same magnitude of admittance. This makes delamination detection via impedance approach not feasible. So, investigation was shifted to detection of intra-ply damage. Damage can be thought of as reduction of stiffness in the whole structure. Fair amount of shift in the modal frequency was observed with respect to damage level. Modal frequency of the structure decreased as well as admittance value lowered with damage increment within the body. Pre-preg manufacturing method is carried out to fabricate composite panel from which samples are cut for testing according to ASTM standards. Panel is fabricated in such a way that enabled 45-degree fiber orientation with respect to the longitudinal axis of specimen. This strategy is taken to easily incorporate damage into the specimen via tensile test. 45-degree fiber orientation will make it easier to create damage compared to the longitudinally aligned fiber sample. Piezo patch is attached to the body and sine sweep voltage is applied to actuate the transducer. It provided voltage drop across the resistor that denoted the coupling effect of the patch with the host structure. Electrical admittance plot expressed response to body deformation actuated by the piezoelectric transducer. Results from finite element modeling and experimentation both indicate shift of frequency value of specific mode for damaged beam from healthy status. Therefore, piezoelectric admittance technique is efficient in detecting damage or degradation within composite structure.
Author: Sazid Irfan Ahmed Publisher: ISBN: Category : Electronic dissertations Languages : en Pages :
Book Description
Structural health monitoring of aerospace structures is becoming vital as lightweight composite materials are increasingly used in aero-structures. Composites have various types of failure modes, which make it even more important to identify fault or damage compared to isotropic materials. Therefore, on-site health monitoring is one of the most preferred methodologies for detecting internal crack or damage at its initial stage to enhance operating safety and reduce repair cost. Recently, piezoelectric transducers are on high demand for on-site health monitoring because of its high bandwidth sensitivity. They simultaneously perform as actuators and sensors and embedded in the structure for real time response indicative of the condition of the structure. Their characteristics show direct coupling between the electrical impedance and structural impedance. The electrical impedance or admittance changes according to modification in mass, stiffness or damping properties of the host body to which the transducer is attached. In this study, plain-weave textile composites are utilized to demonstrate the capability of piezoelectric transducer. The elastic properties of the composite are determined using the fiber tow properties that are derived via the Concentric Cylinder Assemblage micromechanics model. Finite element modeling is done in commercial software ANSYS APDL to observe electrical admittance variation around natural frequency of the entire structure to investigate structure condition. Delamination was studied at first but results show very small shift in frequency of the same mode number for healthy and defective structures along with same magnitude of admittance. This makes delamination detection via impedance approach not feasible. So, investigation was shifted to detection of intra-ply damage. Damage can be thought of as reduction of stiffness in the whole structure. Fair amount of shift in the modal frequency was observed with respect to damage level. Modal frequency of the structure decreased as well as admittance value lowered with damage increment within the body. Pre-preg manufacturing method is carried out to fabricate composite panel from which samples are cut for testing according to ASTM standards. Panel is fabricated in such a way that enabled 45-degree fiber orientation with respect to the longitudinal axis of specimen. This strategy is taken to easily incorporate damage into the specimen via tensile test. 45-degree fiber orientation will make it easier to create damage compared to the longitudinally aligned fiber sample. Piezo patch is attached to the body and sine sweep voltage is applied to actuate the transducer. It provided voltage drop across the resistor that denoted the coupling effect of the patch with the host structure. Electrical admittance plot expressed response to body deformation actuated by the piezoelectric transducer. Results from finite element modeling and experimentation both indicate shift of frequency value of specific mode for damaged beam from healthy status. Therefore, piezoelectric admittance technique is efficient in detecting damage or degradation within composite structure.
Author: Publisher: ISBN: Category : Languages : en Pages : 16
Book Description
Lamb waves have proven to be effective for damage detection by passively listening for emitted signals from crack growth or actively interrogating the structure. Acoustic emission sensors are used for monitoring a wide number of defects in materials such as dynamic strain, crack growth, leakage, corrosion, delamination, and fiber breakage in composite structures. The present paper will present an extensive experimental evaluation of the structural health monitoring (SHM) capability of the PWAS on composite structures of different geometries, environmental conditions, and stress conditions. Results from these experiments indicate that a PWAS based array is capable of detecting low velocity impact damage in composite materials. These experiments showed that abrupt changes in the DI occurred for sensor paths near the impact damage sites, which also indicates that localization of the damage is feasible using PWAS based arrays for SHM. The robustness of the PWAS arrays is demonstrated for damage detection at ambient, cryogenic, and cryogenic temperatures under uniaxial loading using both pulse-echo and pitch-catch methods. Based on these results, a PWAS based SHM array is shown to be a promising method for impact damage detection in composite materials, even in extreme conditions.
Author: J. Bennett Publisher: ISBN: Category : Languages : en Pages : 29
Book Description
Damage detection in metallic and composite structural components is of particular importance in the damage tolerant assessment and the maintenance of aircraft structures. This report describes the use of piezoelectric film for sensing damage in a number of structural components. Three specimens were evaluated, viz.: (1) A rivetted lap joint; (2) A surface crack in an aluminium alloy; (3) An impact damaged composite laminate. The lap joint was chosen to be representative of a fuselage lap joint in modern, wide bodied aircraft. The joint contained multi-site damage repaired with a bonded doubler. Piezoelectric film was applied to the doubler and the underlying damage was detected. The second specimen was a conventional aluminum alloy with surface flaws emanating from a fastener hole. The last specimen was a graphite epoxy composite laminate with impact damage at two locations, i.e. multiple damages sites.
Author: Seth Stovack Kessler Publisher: ISBN: Category : Languages : en Pages : 200
Book Description
(Cont.) These techniques have proven suitable for structural health monitoring applications since they can be applied with low power conformable sensors and can provide useful information about the state of a structure during operation. Piezoelectric patches could also be used as multipurpose sensors to test using a variety of methods such as modal analysis, Lamb wave, acoustic emission and strain based methods simultaneously by altering driving frequencies and sampling rates. Guidelines and recommendations drawn from this research are presented to assist in the design of a structural health monitoring system for a vehicle, and provides a detailed example of a SHM system architecture. These systems will be an important component in future designs of air and spacecraft to increase the feasibility of their missions.
Author: L Ye Publisher: Elsevier ISBN: 1845690621 Category : Technology & Engineering Languages : en Pages : 1121
Book Description
The Asian-Australasian Association for Composite Materials (AACM) has been playing a leading role in the field of composite science and technology since its inception in 1997. AACM aims to encourage the interchange of knowledge in all aspects of composite materials both in the scientific and engineering communities. Following the success of the first three ACCM conferences ACCM 4 was held in Sydney, Australia, in July 2004. Composite technologies for 2020 provides current state-of-the-art achievements and recent advances in composite science and technologies bringing together leading experts and innovators in the field. Nearly 200 selected papers, classified under 18 different categories ranging from general manufacturing and processing techniques to the latest and hottest topics such as nano-composites and eco-bio composites. Together they represent an authorative documentation of current advances in the field of composite materials.
Author: Abdel Salam Hamdy Makhlouf Publisher: Butterworth-Heinemann ISBN: 0128113960 Category : Technology & Engineering Languages : en Pages : 384
Book Description
Handbook of Materials Failure Analysis: With Case Studies from the Electronics Industries examines the reasons materials fail in certain situations, including material defects and mechanical failure as a result of various causes. The book begins with a general overview of materials failure analysis and its importance. It then proceeds to discussions on the types of failure analysis, specific tools and techniques, and an analysis of materials failure from various causes. As failure can occur for several reasons, including materials defects-related failure, materials design-related failure, or corrosion-related failures, the topics covered in this comprehensive source are an important tool for practitioners. Provides the most up-to-date and balanced coverage of failure analysis, combining foundational knowledge and current research on the latest developments and innovations in the field Offers an ideal accompaniment for those interested in materials forensic investigation, failure of materials, static failure analysis, dynamic failure analysis, and fatigue life prediction Presents compelling new case studies from key industries to demonstrate concepts
Author: Mitali G. Shah Publisher: ISBN: Category : Automatic data collection systems Languages : en Pages : 354
Book Description
"The enormous potential that the composite materials can offer to civil infrastructure, mechanical and aerospace industries, and many other sectors has been hindered due to the lack of reliable Structural Health Monitoring (SHM) system capable of detecting damage occurrence and predicting its related effect. Implementation of SHM techniques could substantially reduce the maintenance cost and minimize the likelihood of catastrophic failure of the structures. The main objective of this study is to evaluate the dynamics-based damage detection techniques for the beam-type composite structures using smart piezoelectric materials and modern instrumentation like Scanning Laser Vibrometer (SLV). The study comprises of testing six E-glass/epoxy composite beams with different damage configurations (i.e., delamination, saw-cut and impact damage) using two different sensor systems: (1) Polyvinylidenefluoride (PVDF) sensors and PZT (lead-zirconate-titanate) actuator patches, and (2) SLV system. The experimental tests are conducted using the two sensor systems, and the numerical finite element (FE) analysis is also performed to complement the damage detection. Eight different damage detection algorithms (i.e. absolute difference method (ADM), Damage Factor Method (DFM), Modified Damage Factor Method (MDFM), Damage Index Method (DIM), Uniform Load Surface (ULS), Gapped Smoothing Method (GSM), Strain Energy Method (SEM) and Generalized Fractal Dimension (GFD)) are employed to analyze the experimental and numerical data. Of the eight algorithms, the GSM, SEM and GFD using the ULS curvature mode shapes are emphasized, and a combined static-dynamic approach is further used to magnify the effect of damage. From the damage detection outcomes, it is observed that the PVDF sensor system in which the curvature mode shapes are directly acquired exhibited good sensitivity to damage and could locate damage accurately; while the SLV system proved to be more convenient and effective, and it was capable of scanning large number of points over the entire beam specimens. The damage detection algorithms like the GSM, SEM and GFD based on the utilization of ULS curvatures successfully identified the presence and location of damage without considering the data from the healthy beams as the reference. The GFD provided fairly good results; however, it showed extra peaks at locations other than the actual damage location. The employment of the static-dynamic approach apparently increased the effect of damage (e.g., the delamination), and the application of GSM, GFD and SEM further facilitated to quantify the magnifying effect. In conclusion, dynamic response measurement using two proposed sensor systems and related modal analysis and damage evaluation are demonstrated in this study. The successful implementation of the damage detection techniques, such as GSM, GFD, SEM and combined static-dynamic approach, validates the effectiveness and accuracy of the two sensor systems in damage detection, and they can be integrated with SHM application."--P. iii-iv.
Author: Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
An investigation was performed to develop a self-diagnostic technique using a built-in piezoelectric wafer network to detect damage and to identify the extent of the damage in fiber-reinforced composite plates resulting from foreign-object impact. The principle of the technique was to use built-in piezoelectric wafers as actuators to generate stress waves and also use the neighboring piezoelectric wafers as sensors to receive the propagating waves. The difference in sensor measurements before and after the introduction or impact damage, referred to as scatter, contains information about the location and size of site impact damage. Accordingly, the proposed technique. consists of signal generation, signal processing, and damage identification. In the first part of the study, focus was on thin to moderately thick composites where identifying damage in the thickness direction was ignored and only a single piezoelectric wafer network through the composite plates was used. Diagnostic signals were selected for built-in piezoelectric actuators to generate appropriate Lamb waves to enhance the sensitivity of the sensor measurement to damage and to minimize signal noises due to environments. A signal-processing scheme composed of a smooth filtering and a joint time-frequency analysis was utilized to overcome noise interference and convert sensor measurements into sensor and scatter spectrograms in the time-frequency domain.
Author: Sazid Irfan Ahmed
Author: Sazid Irfan Ahmed
Author: 
Author: J. Bennett
Author: Seth Stovack Kessler
Author: Abu Saeed Islam
Author: L Ye
Author: Łukasz Ambroziński
Author: Abdel Salam Hamdy Makhlouf
Author: Mitali G. Shah
Author: