Anisotropic measurement of short glass fiber-epoxy composites obtained by rotational molding apparatus

It has been almost impossible to make experimentally composite materials wi th randomly oriented fillers of a heavy density in matrix resins of low vis cosity, because the fillers precipitate out at the bottom of the mold due t o gravitation before the liquid resins have time to cure with chemical reac tions. In this paper, a new bi-axial rotational molding apparatus to cure t he resins containing heavy fillers has been developed and the distribution of short glass fibers and their nickel-coated fibers has been investigated (using this instrument). An aminimide compound, adopted as a latent hardene r for epoxy resins, was thermolyzed to generate a tertiary amine for cataly sts and an isocyanate at 130 degreesC and above. The results obtained from SEM cross-section photographs and from fiber orientation measurements with a rotative polarization system of millimeter waves showed a random orientat ion of fibers. The moduli of the composites measured by flexural tests were very close to the values calculated from Nielsen's theoretical equation fo r random orientation in orthogonal directions.