Finite element modeling of polymer curing in natural fiber reinforced composites T. Behzad a , M. Sain b, * a Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ont., Canada M5S 3E5 b Faculty of Forestry/Chemical Engineering, 33 Willcocks Street, University of Toronto, Ont., Canada M5S 3B3 Received 22 November 2005; received in revised form 16 June 2006; accepted 29 June 2006 Available online 2 October 2006 Abstract Plant-based fibers have been selected as suitable reinforcements for composites due to their good mechanical performances and envi- ronmental advantages. This paper describes the development of a simulation procedure to predict the temperature profile and the curing behavior of the hemp fiber/thermoset composite during the molding process. The governing equations for the non-linear transient heat transfer and the resin cure kinetics were presented. A general purpose multiphysics finite element package was employed. The procedure was applied to simulate one-dimensional and three-dimensional models. Experiments were carried out to verify the simulated results. Experimental data shows that the simulation procedure is numerically valid and stable, and it can provide reasonably accurate predic- tions. The numerical simulation was performed for a three-dimensional complex geometry of an automotive part to predict the temper- ature distribution and the curing behavior of the composite during the molding process. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Natural fiber composite; B. Curing; B. Modeling; C. Finite element analysis (FEM) 1. Introduction Natural fibers such as hemp, flax, jute, wood, and sev- eral waste cellulosic products have been used as suitable alternatives to synthetic reinforcements for composites in many applications. These fibers offer specific benefits such as low density, low pollutant emissions, biodegradability, high specific properties, and low cost [1,2]. Many studies have been carried out to develop different manufacturing processes and to study the mechanical per- formances of natural fiber composites [3–7]. The successful production of thermoset composite parts depends upon a proper cure cycle during the molding process that leads to uniform curing and compaction. A few reports in the lit- erature employed numerical analysis to study curing behavior and temperature distribution of synthetic fiber composites during autoclave, resin transfer molding (RTM), and other manufacturing processes. For instance, Guo et al. [8] conducted a one-dimensional transient heat transfer analysis during the autoclave cure cycle for thick carbon fiber/epoxy laminates using a commercial finite ele- ment (FE) software. It was found that the conventional curing cycles should be modified to prevent temperature overshoot. The temperature profiles of a thick unidirec- tional glass/epoxy laminate during an autoclave vacuum bag process were predicted by Oh and Lee [9] using three-dimensional transient heat transfer FE analysis. Then, the viscosity profiles, degree of cure, and resin pres- sure distribution in the laminate were obtained from the results of the heat transfer analysis. Joshi et al. [10] per- formed a transient heat transfer analysis using a general purpose FE software and two user programs to simulate resin cure kinetics of a thick graphite/epoxy laminate. The results showed excellent agreement with the experi- mental data. The modeling and simulation of resin flow, heat transfer, and the curing of multilayer thermoset com- posites during autoclave processing were investigated by 0266-3538/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.compscitech.2006.06.021 * Corresponding author. Tel.: +1 416 946 3191; fax: +1 416 978 3834. E-mail address: m.sain@utoronto.ca (M. Sain). www.elsevier.com/locate/compscitech Composites Science and Technology 67 (2007) 1666–1673 COMPOSITES SCIENCE AND TECHNOLOGY