Automated In-Process Cure Monitoring of Composite Laminates Using a Guided Wave-Based System With High-Temperature Piezoelectric Transducers

Abstract

An in-process cure monitoring technique based on “guided wave” concept for carbon fiber reinforced polymer (CFRP) composites was developed. Key parameters including physical properties (viscosity and degree of cure) and state transitions (gelation and vitrification) during the cure cycle were clearly identified experimentally from the amplitude and group velocity of guided waves, validated via the semi-empirical cure process modeling software RAVEN. Using the newly developed cure monitoring system, an array of high-temperature piezoelectric transducers acting as an actuator and sensors were employed to excite and sense guided wave signals, in terms of voltage, through unidirectional composite panels fabricated from Hexcel® IM7/8552 prepreg during cure in an oven. Average normalized peak voltage, which pertains to the wave amplitude, was selected as a metric to describe the guided waves phenomena throughout the entire cure cycle. During the transition from rubbery to glassy state, the group velocity of the guided waves was investigated for connection with degree of cure, Tg, and mechanical properties. This work demonstrated the feasibility of in-process cure monitoring and continued progress toward a closed-loop process control to maximize composite part quality and consistency.

Monitoring of resin flow front and degree of cure in vacuum‐assisted resin infusion process using multifunctional piezoelectric sensor network

“…[ 13 ] The lineal sensing methods such as direct current, [ 14 ] electrical time domain reflectometry, [ 15 ] optical fiber [ 16–19 ] are fragile and expensive, and the information obtained by lineal sensing is quite limited. The areal sensing methods include dielectric sensor, [ 20–22 ] piezo‐resistive fabrics, [ 23 ] piezoelectric transducers (PZTs) [ 24–27 ] and son on. The dielectric sensor and piezo‐resistive fabrics are designed by the authors and have not been standardized.…”

“…As for the carbon fiber reinforced plastics (CFRP) laminates, the propagation characteristics of Lamb waves such as amplitude and energy velocity in composite laminates are measured to monitor the DOC. [ 25–27 ] Different from the previous works, this study installed several PZT sensors on the mold to obtain Lamb waves signals in a pitch‐catch way, as well as electromechanical impedance (EMI) signals in a self‐excitation and self‐reception way. The schematic diagram of the experimental setup is shown in Figure 1.…”

Guided wave tomography based on least-squares reverse-time migration

“…26,27 Ultrasonic guided wave suits the task, because its dispersion relation is uniquely determined by the material properties. 28 In these problems, material properties are assumed to be constant across the one-dimensional (1D) spatial measurement of guided waves. As a result, the inversion for those material constants only requires the determination of a few parameters.…”

Guided wave-based system for real-time cure monitoring of composites using piezoelectric discs and phase-shifted fiber Bragg gratings

“…Analogous trends have been observed between DEA and guided wave-based cure monitoring, including the identification of minimum viscosity and gelation. 4,5…”

“…The trends of attenuation/amplitude and velocity have been shown to be consistent with newly developed guided wave-based systems. 4–6 Maffezzoli et al. 7 provided an expanded discussion of cure monitoring methods using bulk wave ultrasound.…”