Characterization of polymer composites during autoclave manufacturing by Fourier transform Raman spectroscopy

The superior engineering properties of fiber reinforced polymer matrix composites, primarily the high strength-to-weight ratio, make them suitable to applications ranging from sporting goods to aircraft components (e.g. helicopter blades). Unfortunately, consistent fabrication of components with desired mechanical properties has proven difficult, and has led to high production costs. This is largely due to the inability to monitor and control polymer cure, loosely defined as the process of polymer chain extension and cross-linking. Even with stringent process control, slight variations in the pre-polymer formulations (e.g. prepreg) can influence reaction rates, reaction mechanisms, and ultimately, product properties, in an effort to optimize the performance of thermoset composites, we have integrated fiber optic probes between the plies of laminates and monitored cure by Raman spectroscopy, with the eventual goal of process control. Here we present real-time measurements of two high performance aerospace composites cured within an industrial autoclave.