Influence of leaky vacuum bags on the quality of composite parts made from prepreg material

Leakage in vacuum bags for fibre composite production is a frequently occurring defect, especially in the manufacture of components using the open mould process. The previous limit values for assessing the leak tightness of a vacuum set up are mostly historical and based on empirical values. In this paper, the effects of leaks that have been introduced in a defined manner into a vacuum bag are investigated. The physical processes that occur during curing within the leaking vacuum structure are analysed optically as well as by means of ultrasonic testing and thickness measurement and a better understanding of the effects on laminate quality is generated. It is found that there is a difference between leakages in the vacuum bag only and leakages that affect both the vacuum and release film.