Lab-scale experimental analysis of the cyclic compaction-recovery characteristics of uncured thermoset prepreg

Abstract

During its consolidation, uncured thermoset prepreg is exposed to cyclic loading conditions throughout the various stages of the process chain, including material deposition, vacuum debulking, and curing. One significant challenge involves understanding multilayer prepreg tapes’ compaction behavior to optimise the process’s efficiency and improve the final laminate properties. Automated Fibre Placement (AFP) is a suitable process for the automated manufacture of high-quality aerospace structures with reproducible properties. The compaction analysis offers the potential to reduce subsequent steps during other related compaction stages in the process, such as vacuum debulking or autoclave curing. A cyclic compaction-recovery test that approximates AFP conditions was performed with a rheometer. An experimental analysis was conducted into different parameters’ qualitative influence on uncured multilayer thermoset prepreg samples’ compressibility and their characteristics during load release, using a rheometer on a laboratory scale. The variables manipulated were: temperature, pressure, the number of plies, ply configuration, and tape type. The results showed that temperature strongly influenced the thickness reduction until a compaction threshold was approached, and the pressure level’s effect on the final thickness depended greatly on the temperature. The thickness reduction was greater at higher temperatures until a compaction threshold was observed. Further investigations are recommended to gain insight into the flow mechanism within the sample and its void content after compaction to use the data to optimise the parameters.