Abstract
This paper addresses the major concern which component porosity represents in Vacuum Infusion (VI) manufacturing due to resin gelation at pressures close to absolute vacuum. Degassing is a fundamental step to minimize or even avoid resin outgassing and enhance dissolution of voids created during preform impregnation. The efficacy of different degassing procedures based on vacuum degassing, and assisted by adding a nucleation medium, High Speed (HS) resin stirring and/or later pressurization during different time intervals have been analyzed in terms of final void content is studied. Through a rigorous and careful design of the manufacturing process, outgassing effects on final void content were isolated from the rest of porosity causes and specimens with two clearly identifiable regions in terms of porosity were manufactured to facilitate its analysis. Maximum void content was kept under 4% and porous area size was reduced by 72% with respect to conventional vacuum degassing when resin was stirred at HS; therefore, highlighting the importance of enhancing bubble formation during degassing.
Highlights
In order to bridge the gap between Vacuum Infusion (VI) and Resin Transfer Molding (RTM) in terms of component quality through minimizing void content, this paper explores the efficacy of conventional vacuum degassing, and the benefits of additional auxiliary systems which enhance bubble formation during degassing and dissolution of the remaining micro-bubbles in the volume of resin
The effects of some factors on conventional vacuum degassing have been analyzed through a screening experiment based on a fractional factorial design, with the aim of finding a really effective degassing procedure to minimize porosity in specimens manufactured by VI
A detailed VI process has been defined to allow the direct assessment of degassing efficacy by means of the resin outgassing behavior though final specimen void content
Summary
Vacuum Infusion (VI) is a promising alternative to Resin Transfer Molding (RTM) and even prepreg manufacturing, it presents some drawbacks in terms of quality, such as lower fiber volume fraction, v f , and higher void volume fraction, v0 [1,2]. Referred to as porosity, is crucial in matrix performance. Mechanical properties of Fiber Reinforced Polymers (FRP) such as compression, inter-laminar shear and flexural strengths, and fatigue behavior are seriously affected by void content [3,4,5,6]. If porosity is extended to the surface, even surface finish of FRP components may be altered, deteriorating component aesthetics [7] and later bonding [8]. A previous paper presented a new VI process to which the current paper contributes with further studies [9]
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