Abstract
Among the family of liquid composite molding techniques, bladder-assisted resin transfer molding (BARTM) enables efficient manufacturing of hollow composite parts based on tubular reinforcing textiles. However, resin injection under certain processing conditions can result in high filling times or improper parts and finding the optimal process parameters is often a difficult task. This paper studies the impregnation behavior of a biaxial braided fabric in pressure-driven BARTM under a wide range of injection and bladder pressures. Saturation experiments were accomplished by means of a specifically developed injection test rig comprising an under-sized elastomeric bladder and a monolithic transparent mold. The results obtained show significant influence of the relevant process parameters on local preform compaction, apparent global permeability and filling time. Based on the experiments, a universal moldability diagram was derived that enables identification of admissible and critical operating conditions in BARTM, which supports the finding of optimal part filling settings.
Highlights
The utilization of liquid composite molding (LCM) processes and, in particular, resin transfer molding methods is increasingly gaining importance in modern composite industries
It is shown that an increase in injection pressure for experiments with constant bladder pressure generally causes increasing permeability values, which is more pronounced for lower bladder pressure levels (Figure 8(a))
It should be noted that the highest permeability values were obtained for According to Equation (6), the product of apparent permeability and corresponding injection pressure is inversely proportional to the filling time
Summary
The utilization of liquid composite molding (LCM) processes and, in particular, resin transfer molding methods is increasingly gaining importance in modern composite industries. While under-sized elastomeric bladders can be demolded and reused in the process, the occurrence of membrane stresses during the elastic expansion and their effect on preform compaction should be considered.[6] In BARTM, tubular braided fabrics are typically used as continuous fiber reinforcements for highly loaded structural parts.[5] Preform assembly can be realized by means of manual sleeving-on layup[4,7] or through automated over-braiding,[8,9] where the bladder can directly act as a braiding mandrel. The preform is inserted into the cavity of a two-part mold and compacted by applying a specific pres-
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