Work Item
ASTM WK90080
New Practice for Mode I Dominant Fracture Toughness Fatigue Testing of Sandwich Constructions
1. Scope
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 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 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 an a/N versus Gcmax plot from all of the fatigue loading increments. Knowledge of the fatigue fracture toughness of the facesheet-to-core separations of sandwich composites is of use in material selection, product development, research and development activities, and design allowables.
Keywords
composite materials; sandwich composites; sandwich construction; sandwich; core; facesheet; disbond; crack; separation; mode I; fracture toughness; fatigue loading; fatigue
Rationale
Considerable interest exists in the sandwich composites community, particularly in the CMH-17 (Composite Materials Handbook) Sandwich Disbond Working Group, for a Mode I dominant fracture toughness test method performed under constant-amplitude fatigue loading. The proposed standard practice, based on the proposed Mode I Single Cantilever Beam test method (ASTM WK56166), will be used by the sandwich composites community for measuring the resistance to disbond growth under mode I dominant fatigue loading conditions.
The title and scope are in draft form and are under development within this ASTM Committee.
Work Item Status
Date Initiated: 03-25-2024
Technical Contact: Daniel Adams