Abstract
Fabrication of composite parts from prepregs often requires layup and preparation times of days and even weeks, during which prepregs undergo room-temperature aging. The aging process can compromise compaction, tack, and overall quality of composite parts, and thus a need exists for an accurate and convenient method to monitor the extent of prepreg aging as a function of out-time. Here, we report a method to monitor prepreg age, which involves measurement of changes in glass transition temperature as a function of room-temperature aging time. Samples from three out-of-autoclave prepreg systems were aged in ambient conditions and tested periodically using modulated differential scanning calorimetry. A linear increase in glass transition temperature with prepreg age was noted. Results are discussed in the context of monitoring the chemical aging of epoxy resins that occurs at ambient temperature.
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