Acoustic emission method to ascertain damage occurrence in impacted composites
Inventors
Giurgiutiu, Victor • JAMES, Robin • Joseph, Roshan
Assignees
Publication Number
US-11982643-B2
Publication Date
2024-05-14
Expiration Date
2040-11-23
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Abstract
Employing methodologies and systems to detect damage initiation and growth inside a composite material (matrix cracking, delamination, fiber break, fiber pullout, etc.) wherein damage produces high-frequency acoustic emission (AE) waves that are transported to recording sensors along with relatively lower frequency waves representing the flexural deformation of the impacted composite structure.
Core Innovation
The disclosed invention provides a method and system for detecting damage initiation and growth within composite materials, specifically targeting modes such as matrix cracking, delamination, fiber break, and fiber pullout. This is achieved by utilizing acoustic emission (AE) wave analysis, where high-frequency AE signals produced by damage events are recorded and differentiated from lower-frequency waves that result from flexural deformation in the impacted composite structure. The methodology enables the direct analysis of AE signals in real-time during impact events to ascertain whether significant damage has occurred or if the impact was benign.
A major challenge addressed by this disclosure is the detection and characterization of barely visible impact damage (BVID) in carbon fiber reinforced polymer (CFRP) composites, which are prevalent in aerospace structures. BVID is often undetectable by the naked eye yet can significantly diminish the load-carrying capacity of the structure, leading to catastrophic failures if unrecognized. Traditional impact monitoring systems have been limited to estimating force history and impact location, without offering direct assessment of internal damage.
The core innovation of this patent is a comprehensive acoustic emission-based structural health monitoring (SHM) method. It involves obtaining AE signals following an impact, processing these signals through sensors such as piezoelectric wafer active sensors (PWAS), analyzing waveform signatures and frequency spectra, and differentiating between impact events that cause actual internal damage and those that are harmless. Additionally, the method is capable of predicting future behavior of the composite structure, such as crack propagation, by correlating specific AE signal signatures to different failure modes including fiber cracking, debonding, and delamination.
Claims Coverage
The independent claims cover two main inventive features related to acoustic emission-based structural health monitoring and detection methods for composite structures.
Acoustic emission-based structural health monitoring for composite impact events
The method comprises: - Obtaining at least one acoustic emission signal from a composite structure during a foreign object impact event via at least one Piezoelectric Wafer Active Sensor (PWAS) connected to an acoustic testing device. - Analyzing the acoustic emission signal and its frequency spectrum using post-processing to identify signal signatures generated by the impact. - Differentiating, via signal and mode analysis, between internal damage and benign impacts by interpreting acoustic emission waveform characteristics and frequency content. - Distinguishing between different failure modes or damage types—such as fiber cracking, fiber breaking, fiber pushout, matrix microcracking, debonding, and delamination—based on distinct acoustic emission signatures. - Predicting future crack propagation in the composite structure through the acoustic analysis of the AE signal signatures.
Method for detecting damage in a composite structure using piezoelectric wafer active sensors
The method involves: - Attaching at least one piezoelectric wafer active sensor to a composite structure; generating an impact event by applying a foreign object load. - Capturing at least one acoustic emission signal, including its waveform and frequency spectrum, produced by the impact event, using the acoustic testing device. - Post-processing and analyzing the captured signals to differentiate between types of damage or failure modes (fiber cracking, fiber breaking, fiber pushout, matrix microcracking, debonding, delamination), via analysis of the AE waveform and spectrum. - Predicting future crack propagation in the composite structure through the acoustic analysis of the AE signal.
The independent claims establish inventive features in AE-based methods for real-time differentiation and diagnosis of impact-induced damages in composite structures, utilizing waveform, frequency, and mode analysis to identify, distinguish, and predict damage progression.
Stated Advantages
Provides direct detection of internal damage in composites from analysis of real-time recorded acoustic emission wave signals.
Enables rapid, remote, and real-time assessment to distinguish between damaging and benign impacts, reducing system downtime.
Facilitates differentiation between various failure modes and damage types based on AE signal signatures.
Allows prediction of future behavior such as crack propagation, enabling proactive maintenance and repairs.
Documented Applications
Rapid, remote, and real-time impact monitoring of composite structures.
Conducting ASTM D7136 drop weight impact testing with instrumented composite coupons.
Damage identification from impact monitoring to determine if an impact event has caused damage.
Distinguishing between different types of damage or failure modes in composites based on AE signatures.
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