THERMAL-ANALYSIS OF IN-SITU CURING FOR THERMOSET, HOOP-WOUND STRUCTURES USING INFRARED HEATING .2. DEPENDENT SCATTERING EFFECT

The volume fraction of the fibers present in commercial filament wound structures, formed from either epoxy-impregnated tapes (''prepreg'') or fiber strands pulled through an epoxy bath, approaches 60 percent. Such close-packed structures are near the region that may cause depend ent scattering effects to be important; that is, the scattering charac teristics of one fiber may be affected by the presence of nearby fiber s, This dependent scattering may change the single-fiber extinction co efficient and phase function, and thus may change the radiative transf er in such materials. This effect is studied for unidirectional fibers dispersed in a matrix with nonunity refractive index, and with large size parameter (fiber diameter to wavelength ratio) typical of commerc ial fiber-matrix composites. Only the case of radiation incident norma l to the cylinder axes is considered, as this maximizes the dependent effects. The dependent extinction efficiency is found by solving the d ispersion relations for the complex effective propagation constant of the composites. An estimation of this dependent scattering effect on t he infrared in-situ curing of thermoset-hoop-wound structures is also conducted It is found that the wave interference effect is significant for S-glass/3501-6 composite, and neglect of this effect tends to ove restimate the temperature and cure stare within the material during IR in-situ curing.