ASTM D8067 Picture Frame In-Plane Shear Test

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ASTM D8067 Picture Frame In-Plane Shear Test

ASTM D8067 determines the apparent in-plane shear strength and stiffness properties of flat sandwich constructions with composite face sheets. Core material forms include those with continuous bonding surfaces (such as balsa wood and foams) as well as those with discontinuous bonding surfaces (such as honeycomb).

The ASTM D8067 picture frame in-plane shear test measures the force required to produce a set displacement in a sample of material under controlled conditions. It can be performed on either uniaxial or biaxial specimens, but is most often used on uniaxial specimens.

The square test specimen with corner notches is mechanically fastened to a pinned metal frame along each edge. The frame is loaded in uniaxial tension which produces tensile forces in the frame elements at a 45° angle to the applied tension. These tensile forces act along the edges of the specimen to cause a state of predominantly shear stress to transfer the applied force through the specimen.

Why Perform ASTM D8067?

When followed properly some of the information includes tensile properties such as modulus of elasticity, yield stress, elongation beyond yield point, tensile strength, elongation at break, and energy absorption.

Important Considerations When Using ASTM D8067

This test method can be used to produce face sheet strength data for structural design allowables, material specifications, and research and development applications; it may also be used as a quality control test for bonded sandwich panels.

Failure of the sandwich core-to-face sheet bond preceding one of the previous listed modes is not an acceptable failure mode. Failure originating at the panel corner notches is not an acceptable failure mode. Buckling of the panel prior to face sheet or core failure is not an acceptable failure mode, unless otherwise specified as an acceptable response by the test requestor. The test specimen face sheet thicknesses, core thickness, core material and adhesive material must be selected to avoid the unacceptable failure modes.

ASTM D8067 Test Method

ASTM D8067 subjects a square panel of sandwich construction to forces along the panel edges such that the applied force is transferred through the panel via a state of predominantly shear stresses. Tensile forces are applied using a picture-frame loading fixture. By placing two strain gage rosettes in the center of the specimen, the apparent shear stress-strain response of the panel can be measured. Out-of-plane panel deflection measurements help detect panel buckling.

Procedure A uses a specimen without edge doublers.
Procedure B uses a specimen with four discrete edge doublers.
Procedure C uses a specimen with a continuous edge doubler.

The acceptable failure modes are face sheet fracture, face sheet dimpling, face sheet wrinkling or core shear instability.