ASTM D3039

Overview

ASTM D3039 is one of the most widely used test methods in the composites industry to determine the tensile properties of polymer matrix composites reinforced by high-modulus fibers such as carbon, glass, or aramid. This standardized procedure is essential for quality control, material comparison, and design verification in applications ranging from aerospace to automotive and sporting goods.

This method provides data on ultimate tensile strength, modulus of elasticity, Poisson’s ratio, and failure modes under uniaxial tensile loading.

Why ASTM D3039 Matters

In engineering applications, composite materials are valued for their high strength-to-weight ratio. Understanding how these materials perform under tension is crucial. ASTM D3039 ensures a reliable, repeatable testing framework that manufacturers and researchers can use to characterize material behavior and verify conformance to mechanical performance requirements.

The test is particularly important in:

• Material qualification and certification

• Finite element model validation

• Failure analysis and life prediction

• Process optimization

Test Procedure Summary

1. Specimen Preparation

• Standard specimen dimensions are typically 250 mm (10 in.) long × 25 mm (1 in.) wide for unidirectional laminates.

• Tabs are often bonded to the specimen ends to prevent premature gripping failure.

• Specimens are cut from a cured laminate using machining processes that avoid thermal or mechanical damage.

2. Test Setup

• The specimen is mounted in a universal testing machine equipped with wedge or hydraulic grips.

• An axial extensometer or strain gauges are used to measure strain along the length.

• Tests are conducted under controlled environmental conditions (commonly 23 ± 2°C and 50 ± 10% RH).

3. Loading

• A constant crosshead speed (commonly 2 mm/min) is applied until specimen failure.

• The stress-strain curve is recorded in real-time.

Key Results

From ASTM D3039, the following mechanical properties can be obtained:

PropertyDescription

 Ultimate Tensile Strength (UTS)Maximum stress the specimen withstands before failure

Tensile Modulus (E)Slope of the linear region of the stress-strain curve

Poisson’s Ratio (ν)Ratio of transverse to axial strain

Failure StrainAxial strain at failure point

Failure ModeLocation and nature of failure (e.g., fiber breakage, delamination)

Best Practices & Considerations

• Tabbing: Always use appropriate tab materials to avoid grip-induced damage.

• Alignment: Ensure axial alignment to prevent bending stresses.

• Specimen Conditioning: Precondition specimens to ensure repeatability in humid or extreme environments.

• Multiple Specimens: Use a minimum of five specimens for statistical relevance.

Related Standards

• ASTM D7264 – Flexural Properties of Polymer Matrix Composites

• ASTM D695 – Compressive Properties of Rigid Plastics

• ASTM D5379 – Shear Properties via V-Notched Beam Method

Applications

• Aerospace structural components

• Wind turbine blades

• Automotive panels and structures

• Sports equipment

• Marine and civil infrastructure

Conclusion

ASTM D3039 is a foundational test method in the mechanical characterization of composite materials. By providing crucial tensile property data, it helps ensure the performance and safety of fiber-reinforced polymers across high-performance industries. Proper execution and interpretation of this test are critical for material development, structural analysis, and regulatory compliance.