Effects of glass fibers on light transmittance and color of fiber-reinforced composite

Abstract 

Objectives

The main objectives were: (1) To find out the light transmittance characteristics of fiber-reinforced composites. (2) Determination of color differences between non-fiber-reinforced composites and fiber-reinforced composites. (3) Investigation of relationship between light transmittance and color.

Methods

A commercial microhybrid composite was reinforced with S-type braided glass fibers. The samples were divided into three groups—one was used as the control group, with no reinforcements; the second group was reinforced with a single layer of glass fibers; the third was reinforced with double layers of fibers. Transmittance was measured from 400nm to 700nm for all samples. Color values were also measured for all samples and color differences were determined amongst the three groups, based on the CIE L* a* b* color system. The differences in transmittance, color values and color differences were determined by applying one-way analysis of variance (ANOVA) along with Tukey's HSD. Correlation coefficients were calculated between transmittance at different wavelengths and color values.

Results

There were significant differences in transmittance between the control group and the experimental groups. Color changes were also significant amongst the three groups. The control group appeared lighter than both the experimental groups. Addition of fibers shifted the color of the composite samples towards the +a* (red) and +b* (yellow) regions i.e. towards the longer wavelength regions. Statistically significant correlations were found between wavelength of transmitted beam and color values, especially at longer wavelengths.

Significance

Within the scope of this study, it was found that inclusion of glass fibers reduced the amount of light transmitted through the composite structure. Color was also altered with an increase in chroma component and reduction in lightness.