Void content of PP/CF Wet-laid Nonwoven Composites: Effect of Fiber Content and Molding Conditions, and Void Elimination Mechanism

Abstract

Various wet-laid nonwoven composites have been well-developed in recent decades. However, studies that systematically investigate the factors affecting the void content of wet-laid nonwoven composites are still missing. This paper aims to study the factors affecting the void content of wet-laid nonwoven composites and propose a mechanism for void elimination in wet-laid nonwoven composites. Polypropene (PP) and carbon fiber (CF) were chosen to manufacture PP/CF wet-laid nonwoven composites. An orthogonal experimental design found that the CF content and molding pressure can dominate the void content while molding temperature and time have non-significant effects. Subsequently, this paper proposed that the void elimination mechanism is the compression of impregnated CF network (compression mechanism) instead of the matrix’s infiltration to the dry CF network (infiltration mechanism). In order to validate the compression mechanism, the compression curve of the dry CF network was transformed into curves predicting the void content of the PP/CF nonwoven composites. Comparing the predicted and experimental void content suggests that void elimination follows the compression mechanism.