ASTM C393 – Standard Test Method for Core Shear Properties of Sandwich Constructions by Beam Flexure

Standard Test Method for Core Shear Properties of Sandwich Constructions by Beam Flexure

ASTM C393 specifies a bend testing procedure for sandwich constructions of composite materials in order to analyze the shear properties of the core.

This batch of tests is used as a shear test of the core materials, rather than a flexure test of the entire beam.

ASTM D7250 covers the flexure tests. ASTM C393 is focused on obtaining the core shear strength or the core-to-facing shear strength of the sandwich beam.

These tests may be conducted to determine the sandwich flexural stiffness, the core shear strength and shear modulus, or the facings compressive and tensile strengths.

Tests to evaluate core shear strength may also be used to evaluate core-to-facing bonds.

These testing fixtures follow  a standard method of obtaining the sandwich panel flexural strengths and stiffness.

The sandwich stiffness and core shear modulus may be determined by calculations involving measured deflections of sandwich flexure specimens.

Tests can be conducted on short specimens and on long specimens or on one specimen loaded in two ways, and

the flexural stiffness and shear modulus can be determined by simultaneous solution of the complete deflection equations for each span or each loading.

If the facing modulus values are known, a short span beam can be tested and the calculated bending deflection subtracted from the beam’s total deflection.

This gives the shear deflection from which the core shear modulus can be determined.

Geometry

This test procedure uses a sandwich construction which is flat and beam shaped.

The form of the core material may be continuously bonded such as with foam, or could be discontinuous such as with a honeycomb structure.

Solution

A three point bending fixtureis needed to perform the ASTM C393 test.

The specific dimensions of the span points and the bend fixture are specified in the official ASTM publication.

Analysis

Calculations for ASTM C393 are focused on the shear properties of the core sandwich material.

The core shear strength and shear modulus calculation can be analyzed seperately from the core-to-facing and the entire sandwich beam.

Similar Specifications

ASTM D7250 – Sandwich beam flexural and shear stiffness

ASTM D7249 – Sandwich facing strength