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ASTM C393 Standard Test Method for Core Shear Properties of Sandwich Constructions by Beam Flexure
Last updated April 24, 2025
ASTM C393 Standard Test Method for Core Shear Properties of Sandwich Constructions by Beam Flexure
ASTM C393 is a standard test method for measuring the core shear properties of sandwich constructions through beam flexure. Sandwich panels, which find extensive applications in aerospace, automotive, marine, and construction fields, are composed of two thin face sheets glued to a lightweight core material. The shear strength and shear modulus of the core are important parameters for the mechanical behavior and endurance of these panels. The ASTM C393 test procedure assists engineers and researchers in evaluating these properties correctly by subjecting them to controlled bending forces and recording deflection responses.
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ASTM C393 Introduction
The test procedure gives a consistent methodology for determination of the core shear strength, core shear modulus, and facing bending stiffness of beam-flecatured sandwich structures. It is essential to gain insight into the structural efficacy of sandwich panels for load-bearing situations. The experiment entails placing a beam specimen between two supports and loading it at two equidistant points from the center, making the specimen bend and the core suffer from shear stress. The obtained data enables mechanical properties to be calculated, which are crucial in the selection of material and design validation in engineering fields.
ASTMC393 Test Method
Test Setup
The specimen is supported on two simple supports, and load is applied at two points along the beam span.
Loading Process
Load is applied at a constant rate until failure or until the desired deflection limit is reached.
Measurement and Calculation
Deflection is measured, and equations provided in ASTM C393 are used to calculate core shear strength and shear modulus.
ASTMC393 Equipment and Sample Preparation
Equipment
Universal testing machine, deflection measuring devices, and loading fixtures according to ASTM specifications.
Specimen Dimensions
The sandwich beam specimen must meet dimensional requirements as prescribed, ensuring a balance between core thickness, face sheet thickness, and span length.
Preparation Procedure
Specimens are cut to required size, edges are finished to prevent premature failure, and the samples are inspected for defects or irregularities before testing.
ASTMC393 Results and Interpretation
The properties determined from C393 testing are core shear strength, core shear modulus, and facing bending stiffness. These are determined from the deflection measurements and applied loads, according to the equations and recommendations in the standard. Core shear strength is a measure of the maximum shear stress that the core material can resist before failure. Core shear modulus is the measure of the stiffness of the core in shear and is critical in making predictions for deformation in operational loads. Facing bending stiffness gives an indication of the face sheets’ rigidity and the overall contribution of the face sheets towards the performance of the panel. The results should be interpreted in relation to industry standards or specifications of the material to ensure that the material is fit for purpose.
A number of standards and publications accompany ASTM C393, such as ASTM D7249 for flexural characteristics of sandwich constructions, ASTM D1781 for climbing drum peel tests, and ASTM C365 for compressive characteristics of sandwich cores. Together, these standards contribute to comprehensive mechanical characterization of sandwich panels and core materials.
Applications in Industry
The standard is widely used in industries where lightweight but strong materials are a requirement. In the aviation industry, sandwich panels tested using this method are employed in aircraft fuselage structures and interior components. The automotive sector uses this test for materials in car panels and body structures to optimize performance while cutting weight. In marine construction, sandwich panels offer structural integrity to decks and hulls, where shear properties of the core are vital for long-term durability. Moreover, construction and architectural sectors also depend on this technique to certify materials for strong yet lightweight structural panels, insulation panels, and façades.