Short-term tests on unidirectional fiberglass for ITER pre-compression rings

The unidirectional fiberglass unidirectional composite has been proposed as one of the candidate materials for ITER pre-compression rings. Material samples have been produced and tested for ITER pre-compression ring manufacturing and testing. In 2003, an initial batch was produced, giving interesting results, but presenting a lower limit for the mechanical characteristics of the material. Therefore, a grip system has been developed and tested, which requires longer samples (650 mm) for obtaining reproducible results which meet the standard. This development led to a grip system using 45 degrees fiberglass for grips and INCONEL compression rings for keeping the grips in place. In 2006, in short-term test, the fourth batch resulted in an ultimate tensile strength of about 2200 MPa (room temperature) and a very limited dispersion of results. Tests at a temperature of 77 K resulted in a mean value greater than 2750 MPa with a similar dispersion. From the above results, an allowable stress value of 1000 MPa can be envisaged at the operating temperature. Stress relaxation tests are presently in progress. (C) 2008 Elsevier B.V. All rights reserved.