ASTM D2344
Short-Beam Strength Flexure Fixture
Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates - PDF
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ASTM D2344 – Short Beam Strength Testing of Composites
ASTM D2344 is a widely used standard test method that determines the apparent interlaminar shear strength (ILSS) of reinforced composite materials. This method is especially relevant for fiber-reinforced polymers (FRPs) such as carbon fiber or glass fiber laminates. It is commonly referred to as the short beam shear test.
What Does ASTM D2344 Measure?
The ASTM D2344 test is designed to evaluate the shear strength between layers (plies) in a laminated composite. It helps manufacturers assess:
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Quality of the bonding between layers
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Effect of processing conditions
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Performance under transverse shear forces
This test is ideal for quick quality checks or for comparing different materials or layups.
Test Specimen Dimensions
The standard specifies a short rectangular specimen with a low span-to-thickness ratio (usually 4:1), which induces shear failure rather than flexural failure.
Typical dimensions:
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Length: ~20–30 mm
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Width: ~6 mm
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Thickness: ~2–3 mm (can vary)
Material Types
This method applies to:
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Unidirectional laminates
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Cross-ply laminates
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Woven fiber composites
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Prepreg layups
Test Equipment and Fixtures
Universal Testing Machine (UTM)
A tensile/compression universal testing machine with a suitable load cell (commonly 1 kN to 10 kN, depending on material strength) is used. Precision control and data logging are critical.
Short Beam Shear Test Fixture
The flexure fixture consists of:
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Two support rollers (typically 3 mm in diameter)
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One loading roller applying force at the midpoint
The supports are positioned to give a span-to-thickness ratio of 4:1.
Optional Add-ons
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Environmental chambers for elevated or sub-zero temperature testing
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Video or laser extensometers (optional for research or more advanced analysis)
Test Procedure
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Specimen Placement: Center the specimen across the two lower support rollers.
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Load Application: Apply a compressive force at a constant crosshead speed (typically 1 mm/min) through the top loading roller.
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Failure Mode: The specimen is expected to fail by interlaminar shear, indicated by a sudden load drop.
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Data Capture: Record the maximum load at the moment of failure.
Calculating Short Beam Strength
The apparent interlaminar shear strength (S) is calculated using the following formula:
S = (0.75 × P) / (b × h)
Where:
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P = maximum load (N)
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b = specimen width (mm)
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h = specimen thickness (mm)
Note: The result is reported in MPa or psi depending on the units used.
Common Failure Modes
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Interlaminar shear failure (desired)
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Delamination at mid-plane
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Flexural (bending) failure – indicates improper setup or too high span-to-thickness ratio
High-quality testing will ensure the primary failure is due to shear rather than bending.
Applications and Use Cases
ASTM D2344 is commonly used in:
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Aerospace and defense composites
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Automotive structural components
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Wind turbine blade materials
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Sporting goods and marine applications
It helps engineers compare:
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Different fiber orientations
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Resin systems
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Processing conditions
Tips for Accurate Testing
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Ensure consistent span-to-thickness ratio
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Use sharp, well-aligned rollers
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Watch for bending or crushing failure—adjust setup if observed
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Perform multiple repetitions (5+ specimens) for reliable average results
Related Standards
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ASTM D7264 – Flexural properties of polymer matrix composites
Conclusion
ASTM D2344 is a quick, reliable test for evaluating interlaminar shear strength in composite materials. It plays a critical role in quality control, material comparison, and structural design validation.
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If you're performing short beam shear testing and need the right equipment, we offer turnkey systems, fixtures, and support to get your lab up and running with full compliance to ASTM D2344.
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