ROUND-ROBIN TESTING FOR MODE-I INTERLAMINAR FRACTURE-TOUGHNESS OF COMPOSITE-MATERIALS

This report summarizes the results of several interlaboratory ''round robin'' test programs for measuring the Mode I interlaminar fracture t oughness of advanced fiber-reinforced composite materials. Double cant ilever beam (DCB) tests were conducted by participants in ASTM Committ ee D-30 on High Modulus Fibers and Their Composites and by representat ives of the European Group on Fracture (EGF) and the Japanese Industri al Standards Group (JIS). DCB tests were performed on three AS4 carbon fiber-reinforced composite materials: AS4/3501-6 with a brittle epoxy matrix. AS4/BP907 with a tough epoxy matrix, and AS4/PEEK with a toug h thermoplastic matrix. Difficulties encountered in manufacturing pane ls, as well as conducting the tests, are discussed. Critical issues th at developed during the course of the testing are highlighted. Results of the round robin testing used to determine the precision of the AST M DCB test standard are summarized.