This practice provides instructions for modifying the single cantilever beam test method, ASTM WK56166, to determine the Mode I dominant fracture toughness of sandwich constructions subjected to constant-amplitude fatigue loading. Fatigue loading is performed using the same single cantilever beam test fixture, composite sandwich specimen, and Mode I dominant loading configuration specified in WK56166. Composite sandwich specimens initially are loaded quasi-statically for precracking and to measure the initial specimen compliance and Gc value. A series of constant-amplitude, force-controlled fatigue loading increments are performed, the duration of each increment based upon obtaining a specified increase in specimen compliance. The crack length is measured at the end of each fatigue loading increment, and used to construct a a/N versus Gcmax plot from all of the fatigue loading increments. Knowledge of the fatigue fracture toughness of facesheet to core separations of sandwich composites is of use in material selection, product development, research and development activities, and design allowables.
composite materials; sandwich composites; sandwich construction; fatigue testing, fracture toughness
Considerable interest exists in the sandwich composites community, particularly in the CMH-17 (Composite Materials Handbook) Sandwich Disbond Working Group, for a standard practice focused on fatigue loading of the single cantilever beam test currently being balloted in WK56166. The proposed standard practice will be used by the sandwich composites community for measuring the resistance to disbond initiation and growth under cyclic fatigue loading conditions.
The title and scope are in draft form and are under development within this ASTM Committee.
Developed by Subcommittee: D30.09
Staff Manager: Melissa Marcinowski
Date Initiated: 11-08-2021
Technical Contact: Daniel Adams