Thick-sectioned RTM composite manufacturing: Part I - In situ cure model parameter identification and sensing

In the present work, we validate experimentally the cure simulation of a thick-sectioned composite processed by resin transfer molding (RTM). The simulation was based on an improved version of the model equations presented previously [Michaud, D.J., Beris, A.N. and Dhurjati, P.S. (1998). Curing behavior of thick-sectioned RTM composites. J. Compos. Mat., 32(14): 1273-1296.]. The presence of fiber reinforcement was found to significantly impact the curing behavior of the resin, leading to significant changes from the neat resin kinetic parameters. Thus, experimental processing data from seven 2.54 cm thick laminates were used to characterize the composite's heat transfer and kinetic model parameters not readily computable from pure component values. The apparent initial concentration of inhibitor additives within the resin system decreased almost 80%, possibly due to absorption on the fiber surfaces. The presence of fibers was also found to reduce the extent of polymerization within the system. Key heat transfer model parameters, for both uncured and cured states, were also identified from experimental data. The importance of considering batch to batch variations and the temperature dependence of the resulting model parameters is discussed. In addition to the development and validation of the RTM cure simulation, heat flux sensors (HFSs) were evaluated as a nonintrusive sensor to replace internal thermocouples as a means of measuring internal cure behavior within a thick-sectioned composite.