ASTM C364

ASTM C364 is the definitive standard for determining the edgewise compressive strength of sandwich panels, which are widely used in aerospace, marine, automotive, and construction industries due to their high strength-to-weight ratio. This test method evaluates how well a sandwich construction can resist crushing forces applied along its edges—simulating structural loading in service.

Purpose of ASTM C364

Sandwich constructions typically consist of two strong, thin face sheets bonded to a lightweight but thick core material. ASTM C364 assesses the compressive strength and stiffness of such panels when force is applied in the plane of the panel—edgewise loading—which can cause local buckling, crushing, or core shear failure.

This test helps engineers:

• Compare materials and panel configurations,

• Optimize core and skin materials,

• Ensure compliance with mechanical performance requirements.

Key Applications

• Aircraft floor panels and bulkheads

• Composite marine decks

• Lightweight cargo container walls

• High-speed rail interiors

• Satellite and UAV structural panels

Test Specimen Requirements

ASTM C364 provides guidance on specimen size and preparation:

• Length: Minimum of 50.8 mm (2 inches)

• Width: Sufficient to produce uniform stress and avoid buckling, typically 50.8 mm to 101.6 mm (2 to 4 inches)

• Core thickness: As required by design, but must be representative of the final application

The edges should be cleanly cut and perpendicular to the loading direction. Face sheets and core must be fully bonded, without delamination or visible defects.

Test Equipment

1. Universal Testing Machine (UTM)

A compression-rated UTM is required to perform this test. The UTM must:

• Have a load capacity appropriate for the expected panel failure load (typically 10–250 kN)

• Be equipped with a precision load cell

• Have displacement control and high data acquisition rates to capture failure modes

2. Edgewise Compression Fixture

ASTM C364 recommends using a rigid loading fixture that provides parallel platen surfaces to ensure uniform edgewise loading. The fixture consists of:

• Upper and lower platens, typically made of hardened steel or aluminum

• Alignment guides or self-aligning platens, if needed, to ensure no eccentric loading

3. Instrumentation

• Displacement transducer (LVDT or extensometer) to measure shortening of the specimen

• Digital data acquisition system to record force and displacement

Test Procedure

1. Specimen Conditioning: Panels should be conditioned at standard lab temperature and humidity for at least 40 hours unless otherwise specified.

2. Mounting the Specimen: The panel is placed vertically between compression platens so that force is applied parallel to the core and facesheets.

3. Alignment Check: Verify that the load is applied without inducing bending or torsion. Misalignment can cause invalid results.

4. Loading: Apply compressive force at a constant crosshead speed of 0.05–0.51 mm/min (0.002–0.02 in/min), depending on specimen stiffness and thickness.

5. Data Recording: Continuously record force and displacement until the specimen fails—by buckling, crushing, or delamination.

Result Calculations

1. Compressive Strength

Compressive Strength = Maximum Load ÷ Cross-sectional Area

• Maximum Load is in newtons (N) or pounds-force (lbf)

• Cross-sectional Area = specimen width × specimen thickness

• ​

2. Edgewise Modulus of Elasticity

Edgewise Modulus of Elasticity = (Specimen Length × Slope of Load-Displacement Curve) ÷ Cross-sectional Area

• Slope is calculated from the straight-line portion of the load versus displacement graph

• Make sure all units are consistent when performing this calculation

Typical Failure Modes

ASTM C364 highlights that failure can occur via:

• Core crushing

• Face sheet wrinkling

• Face sheet debonding

• Panel buckling

Understanding the failure mode helps in diagnosing material or manufacturing weaknesses.

Similar or Related ASTM Standards

If you're working with sandwich panels, consider these related standards:

• ASTM C365 – Flatwise compressive strength of sandwich cores (force applied perpendicular to the panel)

• ASTM C393 – Flexural strength and stiffness of sandwich constructions

• ASTM D7249 – Face sheet compressive strength of composite sandwich panels

• ASTM C297 – Flatwise tensile strength (bond integrity between face sheet and core)

Equipment Recommendations

If you're looking to set up an ASTM C364 test in your lab, you’ll need:

✅ Universal Testing Machine (UTM):

• Load capacity: 10 kN to 250 kN

• Compression platens with self-alignment if needed

✅ Custom Edgewise Compression Fixture:

• Flat compression plates with side guides

• Capable of accommodating various panel widths and core thicknesses

✅ Optional Enhancements:

• High-speed cameras for failure analysis

• Environmental chamber for testing under temperature/humidity extremes

• Non-contact displacement sensors (e.g., laser extensometers)

Best Practices and Tips

• Always verify alignment of the specimen to avoid artificial bending.

• Cut specimens with a water jet or high-precision saw to prevent face/core delamination.

• Use lubricated or low-friction platens to minimize frictional constraint at the ends.

• Consider bonding metal end caps to improve load uniformity on short samples.

Summary

ASTM C364 is a critical mechanical test for evaluating the edgewise compressive strength of sandwich panel constructions. It replicates in-service compressive loading conditions found in aerospace, marine, and structural panels. With the right universal testing machine, edgewise compression fixture, and data acquisition system, testing can be done accurately and repeatably.

Whether you’re validating a new core material or comparing fabrication processes, mastering ASTM C364 gives you a reliable metric for real-world structural performance.