On-Line Processing of Unidirectional Fiber Composites Using Radiative Heating: II. Radiative Properties, Experimental Validation and Process Parameter Selection

Abstract

Experimental validation is presented for a detailed thermal model (described in Paper I) for on-line processing of unidirectional fiber composites by surface or volumetric radiative heating. Surface and volumetric radiative properties of unidirectional graphite/epoxy and glass/epoxy are presented: measurements of the complex refractive index of an uncured and cured 3501-6 epoxy resin as a function of wavelength; semi-empirical extinction and scattering coefficients and phase functions for graphite/epoxy and glass/epoxy as a function of wavelength and incident angle, assuming independent scattering; model predictions of the effects of dependent scattering (i.e. electromagnetic wave interference) in graphite/epoxy and glass/epoxy; and measurements of the directional-hemispherical reflectance of AS4/3501-6 as a function of wavelength, incident angle, unidirectional composite orientation, and degree of cure. Experimental temperature histories for in-situ (or continuous) curing of graphite/epoxy, hoop-wound cylinders using infrared (IR) heating at power levels of 5 and 7 kW and mandrel winding speeds of 0.1 and 0.15 m/s are presented. Good qualitative agreement is found between the experimental results and model predictions for AS4/3501-6. Recommended manufacturing process windows for graphite/epoxy and glass/epoxy are presented for several process parameters, such as radiant-source emissive power level and winding speed. Due to their higher radiation absorptivity and lower heat capacity, graphite composites generally have narrower process windows.

Curing Simulation of Composites Coupled with Infrared Heating

“…Because the graphite fibers embedded in the epoxy resin are very strong infrared absorbers over broad spectral ranges at all wavelengths, the composite has strong absorption bands in some portions of the spectrum as a first approach; we have neglected epoxy absorption in this paper [1,2,3,4].…”

“…Thermal radiation was successfully used to produce a high quality polymer matrix in less time [1].We assumed the infrared interaction with the composite is a surfacic heat flux on the top surface [1,2]. The energy equation was coupled with the exothermic heat released during the curing process in order to predict the composite temperature as a function of time and degree of cure.…”

Flow enhancement in liquid composite molding processes by online microwave resin preheating

“…[24,[34][35][36][37][38][39] Other techniques based on the volumetric heating have been successfully used for cure and postcure of composite components, such as induction and infrared heating. [40][41][42][43][44][45] However, no studies dealing with the integration of these two technologies with resin transfer molding (RTM) or vacuum-assisted resin infusion (VARI) processes to enhance the impregnation phase have were in the literature.…”

Fast polymerization at low temperature of an infrared radiation cured epoxy-amine adhesive

“…Instead of these common ways of curing, this present study paves the way to a more universal way of curing, avoiding any additives: infrared-curing. This polymerization method has already been studied in the literature [17][18][19][20][21][22][23], but only when the temperatures induced by infrared radiation are very important. To our knowledge, low temperature curing by infrared radiation (i.e.…”