Fundamentals of breather technology in prepreg consolidation

Breathers have been an integral part of composite manufacturing and repair for nearly 30 years. Yet, despite their long history and almost commonplace usage, the function ofbreathers in composite manufacturing has received little attention. In this study, four different commercial prepreg systems were consolidated in an autoclave to determine the function breathers play in volatile removal, part compaction, and in the final morphology of composite parts. Breathers did not provide a gas path for the removal of volatiles during autoclaving, but were found to facilitate part compaction. In exploring the function of breathers, autoclave volatile evolution was also investigated. In the systems studied, approximately 0.10 weight percent volatiles evolved during a standard autoclave cycle. Volatiles or solvents were shown to dramatically lower the glass transition temperature of the final composite. Prepreg tack was also influenced by solvent removal. Ultimately, this work provides a scientific basis for understanding the function of breathers in composite manufacturing.