Time-Temperature Dependence of Flexural Strength of GRP Laminates

Abstract

This paper is concerned with the time- and temperature dependences of the flexural strengths of the plain fabric glass cloth reinforced laminates (GRP) and the unsaturated polyester resin used as the matrix of the GRP. These properties were measured by constant strain rate tests and creep rupture tests in the temperature range from 60°C to 150°C.
The results obtained are summarized as follows:
(1) The master curves of the flexural strengths for both the matrix and GRP can be constructed, using their thermo-rheological simple properties. As for the time- and temperature shift factors, they are in good agreement each other quantitatively, and also coincide well with those obtained in the previous paper concerning with the creep compliances of these materials.
(2) It was found that the relation between the flexural strengths of the matrix and GRP can be uniquely determined, independent of the conditions of their circumstance such as temperature and strain rate (time).
(3) The master curve of the flexural creep rupture strength of GRP vs. time to failure is in good agreement with that of the flexural strength vs. strain rate.
(4) From the above-mentioned results (1) and (3), the creep rupture strength of GRP is easily estimated from the time-temperature shift factors measurement for the matrix and the constant strain rate tests for GRP.