Exploring the behavior of glass fiber reinforcements under vibration-assisted compaction

Abstract

In this study, a new vibration-assisted approach is proposed for compacting dry fibrous reinforcements in liquid composite molding (LCM). The first steps of LCM processes involve fiber bed lay-up within a rigid mold, followed by the closure of the counter-mold and subsequent fiber compaction. Traditionally, static compaction has been applied to level the thickness of the reinforcement and achieve high fiber volume contents. However, fibrous materials under transverse compression exhibit viscoelastic characteristics that can be exploited through dynamic loading in order to achieve a higher level of compaction. In this work, a vibration-assisted compaction technique has been developed, in which static and dynamic stresses are combined to provide specific compaction conditions. A series of tests allowed exploring the impact of different loading conditions (i.e. static force, dynamic force, and vibratory frequency) on the compaction response of fibrous preforms. The effects of vibration-assisted compaction on various fabric architectures and different numbers of stacked layers were explored as well. The analysis of experimental outputs allows identifying the governing parameters of this new approach. The fiber volume contents obtained reveal that the use of a complex compressive load, composed of static and dynamic forces, can be very effective for the compaction of dry fibrous materials. Although vibration-assisted compaction remains a technology in its preliminary stage, this paper contributes to a better understanding of its potential and provides tools for eventual applications.