Cure kinetics modeling and cure shrinkage behavior of a thermosetting composite (original) (raw)
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Optimization of the Composite Cure Process Based on the Thermo-Kinetic Model
Advanced Materials Research, 2012
High performance composite structures produced by the processes at which the consolidation of the fibres and matrix is done at the same time as the component is shaped. Full curing schedule include a pre-warming for resin liquefaction, next apply of pressure to remove the gas bubbles, and finally consolidation of resin at elevated temperature to its full polymerization. The change in the state of the composite should be made as possible uniformly across the thickwalled products. The complexity of process control is due to unobservability of the rheological state of material in a closed volume of a mould. In this paper we propose a mathematical model of epoxy-based thick-walled composite structure curing. PDE system linking a kinetic equation of the resin cure with heat transfer equation, take into account a phase transition from liquid to gel and further to the solid state. On the basis of transient analysis of the developed model we optimize the temperature control law.
Polymer Composites, 2013
In this article, the optimal design of the thermal cure cycle of a prepreg material has been presented. Three different kinetic methods have been considered to determine the kinetic parameters of the curing reaction of an epoxy/glass prepreg. The capability of these kinetic models in simultaneously predicting kinetic parameters in isothermal and non-isothermal conditions differs with each other. For the simulation of the cure cycle, a zero-dimensional model has been used and coupled with the genetic algorithm to optimize the cure cycle of thin composite parts. The effect of the kinetic models on the optimized cure cycle has been investigated. Of these models, only one model could predict the kinetic parameters outside the experimental temperature regions and resulted in a reliable and acceptable optimized cure cycle. The validity of the optimized cure cycle has been also verified experimentally.
Optimization of the Composite Cure Process on the Basis of Thermo-Kinetic Model
2011
High performance composite structures produced by the processes at which the consolidation of the fibres and matrix is done at the same time as the component is shaped. Full curing schedule include a pre-warming for resin liquefaction, next apply of pressure to remove the gas bubbles, and finally consolidation of resin at elevated temperature to its full polymerization. The change in the state of the composite should be made as possible uniformly across the thick-walled products. The complexity of process control is due to unobservability of the rheological state of material in a closed volume of a mould. In this paper we propose a mathematical model of epoxy-based thick-walled composite structure curing. PDE system linking a kinetic equation of the resin cure with heat transfer equation, take into account a phase transition from liquid to gel and further to the solid state. On the basis of transient analysis of the developed model we optimize the temperature control law. 1 The Prob...
Accurate Cure Modeling for Isothermal Processing of Fast Curing Epoxy Resins
Polymers
In this work a holistic approach for the characterization and mathematical modeling of the reaction kinetics of a fast epoxy resin is shown. Major composite manufacturing processes like resin transfer molding involve isothermal curing at temperatures far below the ultimate glass transition temperature. Hence, premature vitrification occurs during curing and consequently has to be taken into account by the kinetic model. In order to show the benefit of using a complex kinetic model, the Kamal-Malkin kinetic model is compared to the Grindling kinetic model in terms of prediction quality for isothermal processing. From the selected models, only the Grindling kinetic is capable of taking into account vitrification. Non-isothermal, isothermal and combined differential scanning calorimetry (DSC) measurements are conducted and processed for subsequent use for model parametrization. In order to demonstrate which DSC measurements are vital for proper cure modeling, both models are fitted to varying sets of measurements. Special attention is given to the evaluation of isothermal DSC measurements which are subject to deviations arising from unrecorded cross-linking prior to the beginning of the measurement as well as from physical aging effects. It is found that isothermal measurements are vital for accurate modeling of isothermal cure and cannot be neglected. Accurate cure predictions are achieved using the Grindling kinetic model.
2009
This paper deals with the development and the validation of a computational model for the analysis of the thermo-chemical and rheological aspects related to the autoclave cure process of thick carbon-epoxy composite laminate. The transient three dimensional distributions of temperature, reaction rate, degree of cure, and viscosity into the processing material have been evaluated, assuming the time-temperature curve and the heat generation rate due to resin reaction as thermal load and solving the energy balance using a finite element scheme. The rheological behaviour of the processing resin has been studied assuming a three parameters correlation models for the evaluation of the processing material viscosity. A good agreement between present results and data reported in the related literature has been found. The proposed model can be used as an effective tool for analysis and design of optimized thermal cycles.
Effect of CNT addition on cure kinetics of glass fiber/epoxy composite
IOP Conference Series: Materials Science and Engineering, 2018
In present time, developments in reinforced polymer composites have acquired preferential attention for high performance and high precision applications like aerospace, marine and transportation. Fibre reinforced polymer (FRP) composites are being substituted because of their low density, higher strength, stiffness, impact resistance, and improved corrosion resistance. Further laminated composites exhibit superior in-plane mechanical properties that are mostly governed by the fibers. However, laminated FRP composites suffer from poor out of plane properties in some applications. These properties can further be improved by the addition of Nano fillers like carbon nanotube (CNT), graphene and so on. Curing cycle plays a very important role in drawing out the optimum property of glass fiber/epoxy (GE) composite. It is expected that the cure kinetics can further be altered by addition of CNT due to its higher aspect ratio. The main objective of this work is to study the effect of CNT addition on cure kinetics of GE composite as multi-segment adsorption of polymer takes place on the CNT surface. In this study effects of curing parameters on mechanical properties and glass transition temperature of CNT embedded glass fiber/epoxy composite (CNT-GE) has been evaluated. For this study control GE and CNT-GE (with 0.1 wt. %) laminates were fabricated using hand lay-up technique followed by hot compression. The curing parameters that were considered in the present investigation were temperature (80°C, 110°C, and 140°C) and time (0.5 hr, 3 hr and 6 hr). For different combination of above mentioned temperature and time, samples of GE and CNT-GE composites were post cured. Mechanical properties were determined by flexural testing using 3 point bending fixture on INSTRON-5967 and thermal properties i.e. glass transition temperature (Tg) determined by Differential Scanning Calorimeter (DSC) to evaluate the effects of curing parameters. For CNT-GE samples, No much variation observed in flexural modulus with increase in post curing temperature and time, but swift increment was observed in flexural strength at 140°C with increase in post cure time. Elevation in Tg observed with increase in temperature and time duration of post curing; highest Tg noted at 140°C-6hr. Optimum post curing parameters for CNT-GE composite observed to be 140°C-6hr.
Curing Kinetic Parameters of Epoxy Composite Reinforced with Mallow Fibers
Materials, 2019
Knowledge about the curing behavior of a thermosetting resin and its composites includes the determination of kinetic parameters and constitutes an important scientific and technological tool for industrial process optimization. In the present work, the differential scanning calorimetry (DSC) technique was used to determine several curing parameters for pure epoxy and its composite reinforced with 20 vol % mallow fibers. Analyses were performed with heating rates of 5, 7.5, and 10 °C/min, as per the ASTM E698 standard. The kinetic related parameters, that is, activation energy (E), Avrami’s pre-exponential factor (Z), and mean time to reach 50% cure (t½), were obtained for the materials, at temperatures ranging from 25 to 100 °C. Response surfaces based on the mathematical relationship between reaction time, transformed fraction, and temperature were provided for optimization purposes. The results showed that the average curing time used for the production of diglycidyl ether of bis...
Isothermal differential scanning calorimetry study of a glass/epoxy prepreg
Polym Advan Technol, 2009
Isothermal differential scanning calorimetry (DSC) was used to study the curing behavior of epoxy prepreg Hexply 1 1454 system, based on diglycidyl ether of bisphenol A (DEGBA)/dicyandiamid (DICY) reinforced by glass fiber. Cure kinetics of an autocatalytic-type reaction were analyzed by general form of conversion-dependent function. The characteristic feature of conversion-dependent function was determined using a reduced-plot method where the temperature-dependent reaction rate constant was analytically separated from the isothermal data. An autocatalytic kinetic model was used; it can predict the overall kinetic behavior in the whole studied cure temperature range (115-130-C). The activation energy and pre-exponential factor were determined as: E ¼ 94.8 kJ/mol and A ¼ 1.75 T 10 10 sec S1 and reaction order as 2.11 (m R n ¼ 0.65 R 1.46 ¼ 2.11). A kinetic model based on these values was developed by which the prediction is in good agreement with experimental values.
… Science and Technology, 2012
Quantification and understanding of the evolution of chemical shrinkage of thermoset polymers is of crucial importance for modelling of residual strains and stresses. Thermal properties of resin and the strong coupling between chemical reactions and thermal fields lead to non-negligible thermal and curing degree gradients in the part. In this paper, modelling of the volume chemical shrinkages of an unsaturated epoxy vinylester resin and associated glass fibre composites is proposed, by taking into account the coupling between volume variation and thermal gradients. Modelling is also compared with the measurements done with a home-made instrument (PVT–α). Results suggest that chemical shrinkage is non linear as a function of degree of cure. Moreover, for an equal mass of resin, chemical shrinkage of resin carrying fibres is lesser than the neat resin.
Journal of Composite Materials, 2011
Thermal, rheological, and mechanical properties of a commercial carbon fiber epoxy prepreg, Cycom 977-2 UD, were obtained for isothermal cure temperatures ranging from 149°C to 182°C. For each cure profile, an encapsulated-sample rheometer (ESR) was used to measure the storage modulus. Each ESR cure profile was followed by the glass transition temperature ( Tg) test. The degree of cure ( α) during cure and the heat of reaction of the prepreg were obtained using a differential scanning calorimeter (DSC). Combined loading compression (CLC) and short-beam shear (SBS) tests were performed to obtain compressive properties and SBS strength, respectively. It was observed that the compressive properties did not vary significantly for the studied isothermal cure temperatures; likewise, the compressive failure mode was the same for all the CLC specimens. However, the SBS strength for the specimens cured at 149°C was approximately 10% less than that of those cured at isothermal cure temperatur...