ASTM D5961 - Bearing Response of Polymer Matrix Composite Laminates

ASTM D5961 is a testing standard that covers the bearing response of pinned or fastened joints of composite laminates. Connecting individual composite components with rivets or fastener is a common solution for connection of parts in the aerospace industry. ASTM D5961 is used by material designers to determine material specifications for research and development, quality assurance, and structural design analysis.

ASTM D5961 includes four different testing procedures: A, B, C, and D. Procedure A is designed for double-shear tensile loading on a single piece specimen. Procedure B is for single-shear tensile or compressive loading on a two piece specimen. Procedure C is for single shear tensile loading of a single piece specimen, and Procedure D is for double-shear compressive loading on a single piece coupon. The composite coupons are supposed to be balanced and symmetric with respect to their test direction. 

It is important to note that these four testing procedures will give results that are not directly comparable. Due to the larger fastener rotation and higher peak bearing stress Procedure C will yield higher strengths than Procedure B. For protruding head fasteners Procedure D will most likely yield higher bearing results than Procedure C. Procedures A and C produce very similar results.

ASTM D5961 testing is best performed on a high capacity system such as Instron's 100kN 6800 Series floor model equipped with either precision manual (2716-028/030) or hydraulic (2743-401)wedge grips for gripping the loading plates. This standard requires different loading tools for each procedure, usually involving loading plates, pins, and/or fasteners. A set of grips is needed to grip the loading plates.

For more information, download ASTM D5961