ASTM C393 Core Shear Properties of Sandwich Constructions by Beam Flexure

    ASTM C393 Introduction

    ASTM C393 (Standard Test Method for Core Shear Properties of Sandwich Constructions by Beam Flexure) determines the flexural properties and the core shear properties of sandwich constructions. Sandwich constructions consist of light cores and strong facing material, which provides high stiffness and strength. So, these materials are widely used in aerospace panels, marine structures, and transportation components, among others. ASTM C393 measures core shear strength, core-to-facing shear strength, and flexural stiffness of sandwich beams. In addition, the test also provides load-deflection information for stiffness calculations in accordance with ASTM D7250/D7250M. Precise test results aid in the design and materials development, compliance with specifications, and quality control of bonded panels.

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    Get Certified ASTM C393 Testing for Reliable Sandwich Panel Performance

    During service, structural sandwich panels experience bending and shear stresses. Hence, manufacturers need to confirm the core integrity as well as the bonding property prior to product application. Correct testing detects areas of poor bonding, low-density core, and stiffness issues. In addition, laboratory testing certification will enhance the reliability of the products and aid in the qualification of materials.

    Scope of ASTM C393 Test Standard

    • Calculates basic shear characteristics of flat sandwich structures.
    • Test flexural-loaded sandwich beams.
    • Covers all core bonding surfaces (continuous and discontinuous).
    • Uses for foam, balsa wood, and honeycomb core materials.
    • Helps in support and stiffness testing and evaluation.

    Equipment and Sample Preparation

    Universal Testing MachineApplies controlled flexural loading to sandwich beam specimens.
    Deflection Measuring DeviceRecords specimen deflection during beam flexure testing.
    Loading and Support FixturesMaintain proper specimen alignment and load distribution.

    Use of ASTM C393 

    • Tests the shear strength of the core in sandwich constructions.
    • Evaluates key-to-key bond performance.
    • Assists bonded panel quality control programs.
    • Creates data that is allowed for structural design.

    Why Is Core Shear Strength Important in Sandwich Structures?

    Sandwich panels can withstand internal shear stresses during bending, which are controlled by core shear strength. Core materials may be weak and can bend or break under load. Thus, the ASTM C393 results are valuable for deciding on an appropriate core configuration for lightweight structures. Accurate shear data also enhances the safety and structural longevity.

    Testing Procedure and Requirements

    ASTM C393 is a flexural test for flat sandwich beam specimens. The specimen is placed on support spans, and loading noses apply force to the specimen. When testing, the system continuously measures the load and deflection. These measurements are used to calculate core shear strength and stiffness behavior.

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    Specimen ConfigurationFlat sandwich beam specimens contain bonded facing materials and lightweight core structures.
    Flexural LoadingConcentrated loading produces curvature in sandwich facing planes during testing.
    Data CollectionLoad-deflection measurements support stiffness and core shear calculations.
    The image shows a Universal Testing Machine (UTM) equipped with a specialized articulating three-point & four-point bend fixture and displacement sensors for flexural beam tests as described in ASTM C393.
    ASTM C393 Universal Testing Machine (UTM)

    How Does Core Density Influence ASTM C393 Results?

    Shear strength and stiffness performance are directly related to core density. Low-density cores reduce weight and also compromise load-carrying ability. Higher density cores tend to have better stiffness and strength properties, however. Thus, the core density must be reported in ASTM C393 testing to allow correct material comparison.

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    Common Challenges and Troubleshooting

    Multiple parameters affect the accuracy of the ASTM C393 test and must be carefully controlled. Results may be inaccurate due to poor specimen alignment, inconsistent adhesive thickness, and void formation. Moreover, when using thin facings with low-density cores, local loading effects can occur around failure points. Wider load pads with rubber padding could improve load distribution during testing. Other factors, such as environmental conditions, fabrication methods, and specimen conditioning, also influence performance. As a result, laboratories need to have controlled procedures, calibrated equipment, and accurate specimen preparation practices.

    Testing Technique, Process, and Data Collection

    The basic steps of testing are specimen preparation and dimension verification. Then the technicians use the support fixtures inside the testing machine to set the sandwich beam. The loading system then applies flexural force at a controlled rate, and the deflection behavior is recorded by sensors. Operators make continuous observations of load response and specimen deformations during testing. Finally, from the recorded data, technicians determine core shear strength, stiffness properties, and load-deflection characteristics.

    Analysis Results and Interpretation

    ASTM C393 reports results in either SI units or inch-pound units. Typical test reports include core shear and core-to-facing shear, flexural stiffness, and load-deflection curve information. The larger the shear strength value, the greater the resistance to internal failure of the core. The same applies to the stable load-deflection pattern, which is a reflection of the effective stiffness of the sandwich panel. Engineers use the measured value to compare it with the designed value and material specifications to determine the structure’s suitability.

    Link to ASTM C393

    FAQ

    Where can I get the astm c393 tested?
    You can share your astm c393 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm c393 test to various testing techniques.
    Please contact us for a detailed quote for your astm c393 testing needs. Cost incurred to carry out different astm c393 testing methodology depends on the type of raw material; number of samples, coupons, or specimens; test conditions, turn around time etc. Costs of some ASTM testing methods start from $100 and the final value depends upon the factors listed above. Please contact us for the best and latest prices.
    The required number of samples or specimens should comply with the procedure given in the astm c393 standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.
    MaTestLab has a vast testing laboratory network, hence we bring you the best testing facilities in a cost-effective way. We offer considerable discounts (15-20%) to our returning customers based on test volume and frequency.
    The turnaround time for astm c393 test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.
    Malhar Khole
    About Author
    Malhar Khole
    Malhar Khole is a Material Testing Associate at MaTestLab Inc. and holds a postgraduate degree in Material Science and Technology from IIT (BHU), Varanasi.
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