An Integrated Acousto/Ultrasonic Structural Health Monitoring System for Composite Pressure Vessels

Abstract

This paper describes the implementation of a structural health monitoring (SHM) method for mechanical components and structures in composite materials with a focus on carbon-fiber-overwrapped pressure vessels (COPVs) used in the aerospace industry. Two flex arrays of polyvinylidene fluoride (PVDF) interdigital transducers have been designed, realized, and mounted on the COPV to generate guided Lamb waves (mode A0) for damage assessment. We developed a custom electronic instrument capable of performing two functions using the same transducers: passive-mode detection of impacts and active-mode damage assessment using Lamb waves. The impact detection is based on an accurate evaluation of the time of arrival and was successfully tested with low-velocity impacts (7 and 30 J). Damage detection and progression is based on the calculation of a damage index matrix which compares a set of signals acquired from the transducers with a baseline. This paper also investigates the advantage of tuning the active-mode frequency to obtain the maximum transducer response in the presence of structural variations of the specimen, and therefore, the highest sensitivity to damage.

A Novel Differential Time-of-Arrival Estimation Technique for Impact Localization on Carbon Fiber Laminate Sheets

“…In [8,9,10,11], the authors presented a guided-wave ultrasound structural health system based on linear arrays of interdigital piezopolymer transducers bonded to a composite pressure vessel. In that system, interdigital transducers were adopted to perform both damage assessment and impact detection/localization using a simple fixed-threshold technique [8,12].…”

“…In that system, interdigital transducers were adopted to perform both damage assessment and impact detection/localization using a simple fixed-threshold technique [8,12]. …”

“…Since the position of the sensing elements is generally fixed by design, the main sources of error in this calculation are the identification of the Differential Time-of-Arrival (DToA) between the sensors, and the propagation velocity of the impact response signal. The issues related to Lamb wave propagation velocity were already addressed in [8], however that work lacked a thorough investigation of the problem of reliably extracting the DToA from impact response signals affected by spurious contents.…”

A Guided Wave Sensor Enabling Simultaneous Wavenumber-Frequency Analysis for Both Lamb and Shear-Horizontal Waves

“…PVDF interdigital transducers (IDTs) [17,18] and PVDF comb transducers [19] have been applied to curved surfaces. While piezoelectric ceramics are usually brittle and cannot conform to curved surfaces, piezoelectric fiber composites (PFC) [20] with interdigital electrodes can send and receive both Lamb waves [21] and SH waves [16] and can have sufficient flexibility for surfaces with moderate curvature.…”

Composite Plate Phased Array Structural Health Monitoring Signal Reconstruction Based on Orthogonal Matching Pursuit Algorithm

“…Structural health monitoring is an important technology on the performance of structure and damage of detection [1,2]. It uses the sensor technology and advanced signal processing method, in the early time when structural damage occurred, for real-time monitoring of response of the detected structure and properties of the target system.…”