Integrated analysis of liquid composite molding (LCM) processes

Liquid composite molding (LCM) processes have been proven to be cost effective for producing lightweight and high-performance composites with geometrically complex reinforcements. In this study, an integrated analysis was carried out to study two processes in this category, including the continuous resin transfer molding (C-RTM) (i.e. resin injection pultrusion) process and the vacuum assisted resin transfer molding (VARTM) process.; Resin injection pultrusion (RIP) combines the advantages of the conventional pultrusion process and the resin transfer molding (RTM) process. It has attracted much attention in the last decade, due to its great potential for producing composite-profile with constant cross-sectional area, its high productivity, low cost, and zero volatile organic compounds (VOC) emissions during processing. In this study, a friction coefficient model and a volume change model of a vinyl ester resin were developed. An analytical model was developed to predict the resistance force in the injection die using the measured friction coefficient value. The volume change model and the friction coefficient model, combined with the temperature and resin conversion profiles along the die, were used to predict the resistance force in the heating die. The comparison between the analytical and numerical results with the experimental data showed that the models and the simulation tool developed in this study are capable of predicting the pulling force in the entire die with good agreement.; Recently, because of the growing interest of low pressure/low temperature manufacturing processes such as VARTM, low shrinkage molding compounds with the ability to be processed at low temperature and low pressure have attracted considerable interest from the composite industry. However, most low profile additives (LPAs) do not work well for the shrinkage control of unsaturated polyester (UP) in low-temperature processes because of the lack of strong temperature changes during molding. In this work, a novel nanotechnology was developed to achieve zero volume shrinkage of low profile UP resin system cured at room temperature by controlling the selectivity of nanoclay during reaction-induced phase separation. Both temperature-induced phase separation of unreacted UP resin and TEM observation of the cured sample showed that nearly all of the nanoclay platelets resided in the LPA-rich phase. Nanoclay presence increased the reaction rate in the LPA-rich phase because nanoclay could act as a co-promoter in the UP curing system. The increased reaction rate in the LPA-rich phase resulted in the earlier microvoid formation and volume expansion, leading to better shrinkage control of the UP systems cured at room temperature. An in-house built dilatometer was used to observe the volume change profile of UP resin with and without nanoclay. The resulting VARTM panels with improved volume shrinkage control showed better surface quality improvement.