Non-Invasive Measurement of Prepreg Resin Content Using Nuclear Magnetic Resonance

Preimpregnated composite materials (prepregs) are increasingly used in composites manufacture in a variety of industries [1]. Fibers such as carbon, glass, quartz, or Kevlar™ fiber are coated with an uncured resin such as an epoxy, polyester, vinyl ester or polyimide forming the prepreg. The resulting prepreg material is then used at a later time in the manufacture of a composite structure. The prepreg is pliable and readily arranged into forms. Parts are made by collating plies of the prepreg onto a form or in a mold in a desired arrangement, and then further curing the resin phase of the composite material under heat and pressure. A very common form of prepreg referred to as a prepreg tow consists of long continuous bundles of fiber coated in the resin. An example of a flat prepreg tow is shown in Figure 1.