Elastic Anisotropy of FRP Reinforced with Glass Yarn

Abstract

The anisotropy of Young's modulus of FRP reinforced with glass yarns, lying parallel, was first experimentally examined, and then its relation with the elastic constants of the constituents was analyzed by assumption of a mechanical model representing the two phase composite system.
Although Young's moduli increase in each direction with an increase of glass volume fraction, the increase in Young's moduli in a direction making the angle θ=30∼90° to the warp direction are very small, in comparison with those values measured in the direction of θ=0∼15°.
Therefore, the effect of reinforcement on Young's modulus is very small in the direction of angle θ=30∼90°.
The measurement of Young's modulus of the sample shows the minimum value in the direction between θ=45° and θ=60°.
This minimum value is to be accounted for by two main factors the one is the existence of constraint restricting the deformation of the yarn and resin on their contact surface, and the other is the anisotropy of the glass yarn.