Characterization Of Cure Kinetics Research Articles

Cure kinetics characterization of soy‐based epoxy resins for infusion moulding process

AbstractThis study presents the kinetics of the reaction of diglycidyl ether of bisphenol A (DGEBA) based epoxy resin in the presence of epoxidized soybean oil (ESO) cured with triethylene tetramine (TETA). An isothermal differential scanning calorimetric (DSC) study is carried out to propose a model to analyze the cure kinetics of bio‐based resin. The proposed model is also compared with the Kamal model. The results clearly highlight that the proposed model attains a reasonable percentage of improvement in predicting cure data. Adding ESO to the conventional system decreases the reaction enthalpy and increases the activation energy of the system. The outcome of the study confirms the feasibility of the proposed material system for an infusion process. Further, tensile property improvement is obtained through using an infusion process for the proposed material system.

Cure kinetics characterization and monitoring of an epoxy resin using DSC, Raman spectroscopy, and DEA

The use of thick sections of fiber-reinforced polymers (FRPs) is increasing for numerous industrial applications such as wind turbine blades. In situ cure monitoring is very important to directly observe the cure process of FRPs during the manufacturing process. In this work, Raman spectroscopy and dielectric analysis (DEA) are investigated for in situ cure monitoring of an epoxy resin. The cure behavior is first characterized using differential scanning calorimetry (DSC) as a baseline comparison, and the best-fit phenomenological reaction model is determined to describe the cure behavior of the epoxy resin as well as the kinetic parameters. The relationship between Tg and degree of cure is also established. The degree of cure obtained from Raman spectroscopy and DEA under isothermal conditions is compared to that obtained from DSC. A good agreement is observed among the three methods, supporting the potential of these in situ cure monitoring methods during manufacturing. An implementation plan for in-plant monitoring is also discussed.

A study of direct cure kinetics characterization during liquid composite molding

In Liquid Composite Molding (LCM), resin impregnates the fiber preform and it subsequently cures to form the composite part. The curing phenomenon is an exothermic process, and it requires optimization of the mold heating profile to reduce the cure cycle time and the cure-induced thermal stress in the composite part. To optimize and control the cure cycle, it is necessary to obtain the resin cure kinetic parameters, which are usually measured offline by Differential Scanning Calorimetry (DSC) or Fourier transform infrared spectroscopy. These parameters measured from neat resin sometimes vary substantially due to the presence of fiber sizing or resin handling and, hence, curing of the LCM can be different from one batch cycle to another. In this paper, a model-based fitting technique is presented to characterize the cure kinetics during LCM and its accuracy is studied numerically and then is validated with experiments. A non-isothermal cure simulation of a composite part is performed based on a given set of cure kinetic parameters, which are the targets of the fitting model. The Genetic Algorithm is used to determine the cure kinetic parameters by matching the simulated temperature field based on the guessed cure parameters with the temperature history actually experienced by the composite part. An uncertainty in temperature reading, which usually happens in real temperature measurement and control, is introduced to evaluate the accuracy and stability of this characterization technique with respect to various fitting periods during curing stage. Since the mold heating cycle will affect the cure history and the cure kinetics characterization, the influence of the mold wall temperature on the characterization accuracy is also investigated. The numerical results show that, by appropriately choosing the mold heating cycle, one will be able to enhance the accuracy and stability of the cure kinetics characterization within a reduced characterization period. Hence, one may reserve more time for the subsequent online cure optimization and control during the cure cycle. An experimental study is also presented to validate this direct cure kinetics characterization method using Vacuum Assisted Resin Transfer Molding (VARTM) process.