THERMAL AND AIR PERMEATION PROPERTIES OF A CARBON-FIBER TOUGHENED EPOXY BASED PREPREG SYSTEM

This study addresses thermal and air permeation properties of a new to ughened prepreg system. Voids in the uncured prepreg structure can aff ect the void content in the final composite structure. A new, toughene d prepreg system, commercially available for aircraft structural appli cation, was utilized in this study. The prepreg was subjected to therm al and rheological characterization to understand the basic prepreg pr operties. These experiments were followed by a prepreg air permeation study to investigate prepreg processing and its influence on the prepr eg structure. Crosslinking of the resin matrix was monitored with prep reg specimens without extracting resin from the prepreg. Along with th ermal property measurements, the air flow rate significantly decreased in initial static experiments, followed by equilibrium permeability v alues. An air permeation model divided the air permeability into intra laminar and interlaminar permeabilities. Interlaminar air permeation w as found to be more pronounced than intralaminar air permeation in thi s particular prepreg system. These permeation measurement results were explained using optical microscopy, proving that the application of v acuum could eliminate significant porosity in the laminate. Collective ly, understanding prepreg thermal and air permeation properties was co nsidered to be important; the voids in uncured prepreg may cause the v oids in the final composite structure. Voids in the prepreg can be att ributed to the heterogeneity and anisotropy of the toughened prepreg s tructure, resulting from particular prepreg processing techniques. (C) 1997 John Wiley & Sons, Inc.