Coupon Tests of Fibre Reinforced Plastics at Elevated Temperatures in Offshore Processing Environments

A programme of tests has been conducted to characterise the strength reduction of three GRP composite materials as a function of temperature and testing environment.

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 three resins: two epoxies and phenolic. The testing environments were sea water and crude oil condensate. The temperature range tested was ambient to 150°C.

The tests were performed on coupon specimens laminated using fibres in the form of woven mat. The fibres were aligned so as to allow testing in both fibre dominated and resin dominated failure modes. A novel environmental tensile testing facility was developed for this work, and this is described briefly.

Results are presented for the strength of the three materials as a function of temperature in each failure mode when tested dry. These are then compared with equivalent results for the specimens tested in the liquid environments. This is the first reported measurement of GRP strength in liquid environments at these very high temperatures.

It is demonstrated from the results that strength reduction is exhibited predominantly in the matrix dominated failure mode, though a small but significant strength reduction is also seen in the fibre dominated mode. Causes for these strength reductions are identified as lowered glass transition temperature and degradation of the glass and glass/resin interfaces respectively. The strength reductions for each combination of material and environment are quantified.

Finally, appropriate limits to operating temperature are suggested for each material when used in an offshore environment.