On the evolution of the distribution of entrapped air at the tool/first ply interf‘ace during lay-up and debulk

Abstract

Air entrapped during the material deposition stage of prepreg layup can contribute to voidage in the cured laminate, which is a major factor in determining the quality of the resulting laminates and components. Removal of this entrapped air is therefore a priority to achieve maximum part performance. To date, there does not appear to have been any consistent study of the processes by which voids can be entrapped. This paper seeks to address this by presenting direct observations of the contact between a glass tool surface and the first ply of carbon fiber prepreg laid down onto it. The entrapment of air between the tool and ply is investigated, in terms of its distribution and evolution during debulk under vacuum at room temperature. A counterintuitive inverse relationship between initial area of contact and the final level of entrapped air was observed, with higher levels of initial contact leading to higher final levels of entrapped air. An initial examination was also carried out to review the effects of ply terminations and bagging practices on air entrapment.