Dynamic viscoelastic properties of photo-activated composite resins containing short glass fibres

The dynamic shear modulus in torsion (G'), water absorption, thermal expans ion and residual monomer of the reinforced materials produced by adding fou r short glass fibres (19 mum in mean diameter and 86.1-763 mum in mean leng th) and one spherical E glass (11.1 mum in mean diameter) were examined and discussed in comparison with those of the materials without filler. G' of short fibre reinforced composites increased with fibre length and reached a maximum value near 382 mum for a dry specimen and near 156 mum for a wet o ne. In addition, the coefficient of thermal expansion of the fibre reinforc ed composites and the amount of residual monomer decreased considerably com pared with those of composites containing spherical glass. There was no sig nificant difference in water absorption between the fibre reinforced compos ites and the composites containing spherical glass. Therefore, it was concl uded that the reinforcement method of adding short glass fibres is favourab le for improving the viscoelastic properties of the materials.