On-Line Processing of Unidirectional Fiber Composites Using Radiative Heating: I. Model

Abstract

Thermal radiation is a clean, flexible, efficient and effective means to supply energy to process a composite on-line. Radiative transfer in high-fiberdensity, unidirectional composites is complex, if analyzed completely. A detailed thermal model for on-line processing of unidirectional fiber composites by surface or volumetric radiative heating is presented. The physical geometry and imposed thermal and radiative boundary conditions correspond to a unidirectional, hoop-wound cylinder. In-situ (or continuous) curing of thermosets or on-line consolidation of thermoplastics is represented by the inclusion or omission, respectively, of the exothermic, chemical energy release term in the energy equation. Numerical results are presented for the temperature and degree of cure of graphite/epoxy and glass/epoxy cylinders. The effects of: surface or volumetric radiative heat flux; radiant-source emissive power level and efficiency; radiative emission from the composite; exothermic, chemical energy release; radiation’s angle of incidence; and independent and dependent scattering in the composite’s interior are presented. Validation of the model is presented in Part II of this paper, as well as recommended manufacturing process windows for process parameters, such as radiant-source emissive power level and winding speed. Part II also includes surface and volumetric radiative properties of unidirectional graphite/epoxy and glass/epoxy composites that were used in the numerical simulations.

Simulations of an Infrared Composite Curing Process

“…Cosson et al [7] developed software called Rayheat in order to predict the distribution of the radiative intensity in PET preforms. Chern et al [1][2][3][4] successfully studied the radiative curing process of hoop-wound cylinders of graphite/epoxy and glass/epoxy. Previously, we have studied the curing process of a composite, the physical geometry of which corresponds to a carbon/epoxy block, manufactured by the LRI process.…”

“…Carbon fibers embedded in the epoxy resin are very strong IR absorbers over broad spectral ranges at all wavelengths, while the composite has strong absorption bands in some portions of the spectrum. [1] The mean value of the spectral reflectance of the carbon/epoxy system is 15%, as taken from the literature. [2] Ray Tracing…”

“…In our ray tracing software, assumptions found in the literature are made for the different optical properties of lamps, reflectors, [10] recovery surface and the carbon/epoxy system. [1,2] They are referenced in Table 1 below. The ray tracing method has been validated in a previous work in the laboratory [7] with an analytical solution given by view factor.…”

“…Because of their good adhesive properties, superior mechanical, chemical and thermal properties, and resistance to fatigue and microcracking, they produce high performance composites. Since it is necessary to optimize the manufacturing time and costs and to determine the performance of these composites, some researchers [1][2][3][4] have studied infrared (IR) heating for the polymerization process. Others [5,6] have used IR energy for the preheating process.…”

“…Consequently, for the production of high performance composites, it is necessary to know the thermal behavior of the composite during curing. The most detailed models for the curing process of composites using IR heaters have been presented by Chern et al [1][2][3][4] They measured the radiative properties of graphite/epoxy and glass/epoxy systems and modeled the radiative heat transfer in the glass/epoxy system as a volumetric radiation transport. Therefore, IR interactions with the graphite/epoxy system were modeled as a surface radiation transport.…”