Tensile Strength Testing of GRP Pipes at Elevated Temperatures in Aggressive Offshore Environments

A programme of tests has been conducted to characterize the strength reduction of two GRP composite materials in the form of filament wound pipes as a function of temperature and testing environment. This complements previous work on the same materials using coupon specimens [1].

The GRP materials and testing environments were selected to be of maximum relevance to the offshore industry. The materials were E-glass fibre reinforcement in matrices of two epoxy resin systems. The testing environments were sea water and sea water with dissolved CO₂ and H₂S gasses. The temperature range tested was ambient to 150°C.

The tests were performed on specimens of commercial filament wound pipe loaded in pure axial tension. A special purpose testing facility was developed for this work, and this is described briefly.

Results are presented for the strength of both materials as a function of temperature when tested dry and a quantitative discrepancy noted with the previous results obtained using coupon specimens. Results of further tests conducted to investigate this phenomenon are presented and a suggested explanation is proposed. Further results are presented for the strengths of the materials in the test environments which are shown to be in qualitative agreement with the previous coupon tests.

It is shown that the axial strength of GRP pipes is significantly reduced at elevated temperatures, that the degree of this reduction is dependent on the matrix material and is magnified by sea water absorption and that dissolved CO₂ and H₂S have little effect.