Thick-Sectioned RTM Composite Manufacturing: Part I – In Situ Cure Model Parameter Identification and Sensing

Abstract

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.

Identification of conductivity in inhomogeneous orthotropic media

“…• Kinetic model: The more applied model for a variety of resins is Kamal's model (1974), see also Dusi et al (1987), 27) where the heat capacity ρc p and thermal conductivity K, assumed for simplicity to be isotropic, are defined as…”

Process Induced Defects in Liquid Molding Processes of Composites

“…While selecting process parameters can be straightforward for thin composite laminates, thick laminates often require more sophisticated methods. A possible approach has been to use numerical simulations based on experimentally validated constitutive models to optimize the cure process parameters (Alexandric et al, 2016;Baran et al, 2017;Bogetti and Gillespie, 1991;Khoun and Hubert, 2010;Michaud et al, 2002;Nielsen et al, 2013;Rai and Pichumani 1997a;Rai and Pichumani, 1997b;Rai and Pichumani, 1997c).…”

“…Building on this effort, a number of researchers adapted these advances in numerical simulation methods to the cure step of LCM processes, often following the impregnation (Khoun and Hubert, 2010;Michaud et al, 2002;Mostafa et al, 2017). In addition to optimizing cure, researchers aim to reduce residual stresses and limit the occurrence of cure induced defects (Baran et al, 2017;Dong et al, 2004;Khoun and Hubert, 2010;Mostafa et al, 2017;Nielsen et al, 2013;Ruiz and Trochu, 2006).…”

Vacuum assisted resin transfer molding (VARTM) in polymer matrix composites

“…The exponents m and n are ranged between zero and two, and m + n = a & a ≅ 2. 18 Table 10.1 lists some example values of the cure kinetic parameters for an epoxy resin and an unsaturated polyester resin. The cure kinetic parameters can be characterized by using Differential Scanning Calorimeter (DSC) 17 or being directly fi tted from the temperature history of a VARTM experiment.…”