The application of 3D woven reinforcements for liquid composite molding processes

  • Hussam Alhussein

Student thesis: Master's Thesis

Abstract

In liquid composite molding (LCM) processes, the dry fibrous reinforcement contained in a closed mold is injected by a liquid polymer resin. The liquid resin is forced to flow between the dry fiber gaps and bundles to impregnate the reinforcement and to create composite parts after subsequent cure of the resin. The compaction response and permeability of fibrous reinforcements is fundamental to LCM processes, given that these fabric properties determine the part thickness, fiber volume content and mold filling time and patterns. In this study, the compaction response and permeability of three different 3D woven carbon fiber reinforcements (orthogonal, angle interlock and layer to layer) was studied, each having a different weave style and z-binder pattern. For all reinforcements, single and multiple cycle compaction experiments were conducted on dry and saturated samples. The orthogonal preforms were more difficult to compact to the target fiber volume fraction of 0.65. Cyclic compaction tests were conducted to highlight the importance of permanent deformation in the reinforcements, when higher fiber volume content is desired in an LCM process. In-plane radial and through-thickness permeability data were obtained. The orthogonal and angle interlock fabrics exhibited greater levels of anisotropy in the plane of flow. The effect of cyclic compaction on permeability was greater in the orthogonal and angle interlock reinforcements. A high performance, toughened, single part epoxy resin system was also characterized. The cure kinetics and rheology tests were conducted under dynamic and isothermal conditions. The experimental data was modelled using autocatalytic and castro-makosco models respectively. A VARTM instrumented tool was developed to monitor the pressure and thickness variations during an infusion process. The pressure evolution during VARTM process was accurately predicted by simulations. The thickness results show that, fiber lubrication effect was minimal in the orthogonal and angle interlock fabrics, mainly due to restricted motion of the fiber tows. An RTM mold was machined for the part manufacture. The flow rates and injection pressures were monitored during the full molding cycle. The RTM mold filling simulations are also presented.
Date of AwardDec 2015
Original languageAmerican English
SupervisorRehan Umer (Supervisor)

Keywords

  • Compaction; Fiber Volume; Fiber Volume Fraction; Permanent Deformation.

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