TY - BOOK

T1 - Inline Process Monitoring Using Near-Infrared Spectroscopy in Liquid Composite Molding Processes: Measurement and Analysis of Critical Parameters in Epoxy/Amine Resin Systems

AU - Salzmann, Moritz Levin

N1 - no embargo

PY - 1800

Y1 - 1800

N2 - Increasing demands for quality assurance, process stability, and control create the need for efficient capture, processing, and analysis of process- and product-relevant measurements during manufacturing, i.e., inline. This often brings economic and ecological benefits through reduced waste and shorter process times. Which parameters are measurable inline depends on the respective technology. One technology that has been scarcely investigated for inline monitoring in the processing of fiber-reinforced polymer composites but is broadly applicable is near-infrared spectroscopy. It utilizes combination and overtone vibrations of functional groups induced by electromagnetic waves in the range of 750-2500 nm. From the measured spectra, parameters can be determined using partial least squares regression, which correlate with the concentrations of functional groups in the measurement volume. In this study, application possibilities of is near-infrared spectroscopy for monitoring liquid composite molding processes are investigated. Liquid composite molding processes were chosen as an example because the essential process steps related to the resin system can be well measured here. Additionally, it allows the consideration of different but relevant measurement scenarios, such as on the pure resin system, through films, or in closed molds. Inline measurements included the fiber moisture of natural fibers, the resin mixing ratio, and the degree of cure. Furthermore, it was investigated how the mixing ratio and degree of cure influence each other, as the determination of both parameters is based on the same functional groups. Miniaturized spectrometers from the NIRONE series were used. These are characterized by low weight and cost, as well as simple handling. However, they have increased measurement time and poorer physical resolution compared to classical process spectrometers. In the course of this work, methods for determining the necessary reference values were established for the three mentioned parameters. Regression models for predicting the measured values were successfully developed for all three parameters. The performance of the miniaturized spectrometers and the wide application possibilities of near-infrared spectroscopy for process monitoring of fiber-reinforced polymer composites processing were successfully demonstrated.

AB - Increasing demands for quality assurance, process stability, and control create the need for efficient capture, processing, and analysis of process- and product-relevant measurements during manufacturing, i.e., inline. This often brings economic and ecological benefits through reduced waste and shorter process times. Which parameters are measurable inline depends on the respective technology. One technology that has been scarcely investigated for inline monitoring in the processing of fiber-reinforced polymer composites but is broadly applicable is near-infrared spectroscopy. It utilizes combination and overtone vibrations of functional groups induced by electromagnetic waves in the range of 750-2500 nm. From the measured spectra, parameters can be determined using partial least squares regression, which correlate with the concentrations of functional groups in the measurement volume. In this study, application possibilities of is near-infrared spectroscopy for monitoring liquid composite molding processes are investigated. Liquid composite molding processes were chosen as an example because the essential process steps related to the resin system can be well measured here. Additionally, it allows the consideration of different but relevant measurement scenarios, such as on the pure resin system, through films, or in closed molds. Inline measurements included the fiber moisture of natural fibers, the resin mixing ratio, and the degree of cure. Furthermore, it was investigated how the mixing ratio and degree of cure influence each other, as the determination of both parameters is based on the same functional groups. Miniaturized spectrometers from the NIRONE series were used. These are characterized by low weight and cost, as well as simple handling. However, they have increased measurement time and poorer physical resolution compared to classical process spectrometers. In the course of this work, methods for determining the necessary reference values were established for the three mentioned parameters. Regression models for predicting the measured values were successfully developed for all three parameters. The performance of the miniaturized spectrometers and the wide application possibilities of near-infrared spectroscopy for process monitoring of fiber-reinforced polymer composites processing were successfully demonstrated.

KW - Near Infrared Spectroscopy (NIR)

KW - Liquid Composite Moulding (LCM)

KW - Process Monitoring

KW - Degree of cure

KW - Nahinfrarotspektroskopie (NIR)

KW - Flüssigimprägnierverfahren (LCM)

KW - Prozessüberwachung

KW - Aushärtegrad

M3 - Doctoral Thesis

ER -