| 摘要 |
PROBLEM TO BE SOLVED: To obtain a cryogenic spacer that exhibits a greatly improved compression stress retention and a reduced cooling shrinkage, maintains a high initial plane pressure in assembling, and thus enhances the stability of a magnet, by cutting an inorg. fiber-reinforced plastic in the direction perpendicular to fibers and treating the cut plastic under pressure. SOLUTION: A fiber-reinforced plastic is obtd. by preparing a resin prepreg sheet reinforced with inorg. and org. fibers in one direction or with a fabric, preparing a laminate contg. inorg. fibers alone or a laminate of inorg. and org. fibers, and press-molding the laminate. The resultant molded item is cut in a direction perpendicular to the fibers into a suitable size. In the case of a molded item contg. inorg. fibers alone (the values in parentheses mean the case of a molded item contg. both org. and inorg. fibers), a compression load of 30-100 MPa (15040 MPa) is applied for 10-30 sec to give a cryogenic spacer, of which the stress retention after 48 hr at 20 deg.C under an initial compression load of 50 MPa is 96% (92%) or higher and the coefficient of thermal expansion under no load is 15×10<-6> / deg.C(2×10<-6> / deg.C). |
