Rate and temperature dependent compaction-creep-recovery and void analysis of compression molded prepregs

Abstract

This study investigates the compaction-creep response of a glass/epoxy prepreg system at different temperatures, pressures, and compaction speeds, using a compaction fixture with heated platens, housed in-situ in an X-ray computed tomography (XCT) machine. It has been shown that by increasing the compaction speed from 0.1 mm/min to 1 mm/min, the total strain, the percentage of compaction creep and the resulting permanent deformation increased for all of the temperature and pressure conditions considered in this study. It was noted that for all compaction speeds and pressures, the percentage of compaction-creep increases from 25 °C up to 55 °C and then decreases with further increases in temperature. A decrease in creep deformation with post creep-thickness recovery, due to the resin squeezing out from the prepreg, was observed at higher temperatures. The void content in the post-creep, fully cured laminates was determined using an analytical model, the results of which were compared with XCT-developed geometrical models. Good agreement between both approaches was observed, with differences in void content results of less than 12% being recorded. The optimum process parameters (55 °C, 0.3 MPa and 0.5 mm/min) were identified in compression molded prepreg samples to choose the first isothermal dwell period . The combination of these process parameters resulted in moderate levels of compaction-creep and permanent deformation as well as a low void volume fraction in the test samples. • Rate dependent thermo-mechanical compaction-creep tests were performed on uncured glass/epoxy prepreg samples. • Percentage of compaction-creep and permanent deformation are found to be increasing with the increase of compaction speed. • Void volume fraction was determined in cured samples using analytical and XCT-aided geometrical models and compared. • Normal distribution statistical analysis was employed to study the size and shape of individual voids.