Temperature and Cure in Pultruded Composites Using Multi-Step Reaction Model for Resin

Abstract

A numerical model has been developed to analyze the temperature and degree of cure profiles in pultruded composites. In pultruded composites the resin plays an important role in holding the fibers together in a structural unit and also transferring and distributing the applied load to the fibers. The degree of cure of the pultruded composite is an important phenomenon in the manufacturing process since it can be related to the mechanical properties. Therefore, the degree of cure of the resin plays a crucial role in the pultrusion process. The chemical reaction of the resin determines the degree of cure as well as the exothermic energy released by the resin. A one-step reaction model has been employed for the resin system in most of the previous research. For some resin systems, a one-step model may not produce good results; therefore, it was decided to pursue a multiple-independent-step reaction model that more closely follows the actual behavior of the resin. In this research, the effect of an approximate multiple-independent-step reaction model for the thermoset epoxy resin SHELL EPON 862/W was studied. The numerical model utilized a fixed control volume based finite difference approach [1]. This technique was used to solve the coupled, non-linear, three-dimensional steady-state energy and species equations for a cylindrical geometry. The species equation(s) utilized both a one-step Arrhenius reaction rate model as well as a multiple-independent-step Arrhenius reaction rate model for the resin. The kinetics parameters of the resin for a one-step reaction model were obtained from the differential scanning calorimeter (DSC) scans and for the multistep model a regression fit was made to obtain the kinetic parameters from the DSC scans. The numerical model was used to predict the temperature and degree of cure for the pultruded composite both inside the die and in the post-die region. These numerical results were compared with experimental measurements. The processing variables examined in this study were die-wall temperature setting, pull speed and fiber volume fraction.

Effects of additives on the cure kinetics of vinyl ester pultrusion resins

“…Subsequently, Trivisano et al 41 proposed and experimentally verified a kinetic submodel necessary for the development of a mathematical model characterizing the curing of epoxy resin during pultrusion. Valliappan et al 42 investigated and verified the multiple-independent-step model describing the polymerization of epoxy resin. Suratno et al 43 proposed a mathematical model of carbon/epoxy composite pultrusion and used it to solve the heat transfer problem.…”

Cure kinetics and rheology characterization of soy‐based epoxy resin system

“…Consequently, a variety of phenomenological models for cure kinetics and rheology have been proposed for different resin systems in the literature. The analytical models of cure kinetics and rheology have found wide applications in numerical simulations of composite manufacturing processes 3, 11–15. In our previous study,1–3 the focus was on the curing of soy composites with amine curing agent.…”

The effect of thermal contact resistance on the thermosetting pultrusion process

“…the centerline temperature of the composite is initially lagging behind the die temperature, however during the curing the composite temperature exceeds the die temperature due to the internal heat generation of the resin. As a means of supporting the numerical thermo-chemical modeling of the pultrusion process, experimental studies of various composite profiles have been carried out in [19][20][21][22][23][24][25][26][27].…”