<title>Characterization of polymer composites during autoclave manufacturing by Fourier transform Raman spectroscopy</title>

Abstract

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 ofpolymer 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 ofthermoset composites, we have integrated fiber optic probes between the plies of laminates and monitored cure by Raman spectroscopy, with the eventual goal ofprocess control. Here we present real-time measurements oftwo high performance aerospace composites cured within an industrial autoclave.

Study of the Degree of Cure through Thermal Analysis and Raman Spectroscopy in Composite-Forming Processes

“…The ratio between the intensities of both D and G bands gives us an idea of the crystalline order of the sample. The crystalline size, L a , is derived from the Knight formula [14,15], La(nm)=false(2.4×10−10false) λ4(IDIG)−1 where λ is the laser line wavelength in nanometer units, and I D and I G are the intensities of the D and G bands, respectively [16,17]. The values for the crystalline order and crystallite sizes for the composite samples with different cure degrees are displayed in Table 8.…”

Cure kinetics of epoxy resin used for advanced composites

“…Many experimental techniques such as differential scanning calorimetry (DSC)2–20 and Fourier‐transform infrared spectroscopy (FTIR)20–23 are commonly used to study the cure reaction of thermoset polymers. DSC is the most widely used experimental technique to obtain the degree and reaction rate of cure of thermosetting resins.…”