A Reliable Standard Approach for Determining Compressive Properties of Composite Materials

The increasing use of advanced composite materials in industrial applications has made it essential to accurately determine their mechanical behavior under compressive loads. The ASTM D6641 Combined Loading Compression (CLC) Test Method is an internationally recognized standard specifically developed to measure the true compressive strength of fiber-reinforced composite materials while minimizing buckling effects. The correct implementation of this standard strongly depends on the mechanical stability, measurement accuracy, and control capability of the testing system used.

Primary Purpose of the Device

In ASTM D6641 compliant CLC compression tests, the DVT FU D NU Universal Testing Machine is used to apply controlled and stable compressive loads to the specimen. The system is designed to safely terminate the test when fracture, failure, or a predefined displacement is reached. By maintaining precise axial alignment and load stability, the device ensures reliable and repeatable compressive test results.

What Is the CLC Compression Test?

The CLC compression test is based on applying a combination of end loading and shear-supported side loading to the specimen. This combined loading approach significantly reduces premature buckling and provides a more uniform stress distribution compared to conventional compression test methods.

Importance and Objective of the Test

The ASTM D6641 method enables accurate determination of the compressive performance of composite materials. Tests performed using the DVT FU D NU Universal Testing Machine provide dependable data for material comparison, production quality monitoring, and engineering validation studies. These results directly contribute to improved product reliability and structural safety.

Scientific Principle of the Test

The test operates on the principle of combined loading. The specimen is precisely aligned within the rigid mechanical structure of the DVT FU D NU Universal Testing Machine, which features a four-column, dual-screw system. Axial compressive load is applied in a controlled manner, ensuring homogeneous stress distribution along the specimen. A force measurement accuracy of ±0.5% and a displacement resolution of 0.001 mm allow detailed analysis of elastic and plastic deformation behavior.

Operation of the Device

ASTM D6641 CLC compression tests are easily configured through the touchscreen interface of the DVT FU D NU Universal Testing Machine. Test speed can be adjusted between 0.001 and 500 mm/min, and force-controlled speed regulation (N/s) enables precise load application. The system automatically stops upon specimen fracture, failure, or when the preset displacement limit is reached. The rapid return function significantly reduces cycle time in sequential testing, while the emergency stop button ensures operator safety at all times.

Technical Specifications

The DVT FU D NU Universal Testing Machine features a robust and maintenance-free mechanical design, ensuring long-term reliability. For tensile tests, the movement direction is upward. Measurement units include kN, Newton, kg, and MPa. The standard software supports multiple languages, including Turkish, English, French, Italian, and Russian. The system operates on a 3-phase 380 V, 50 Hz power supply, with a maximum power consumption of 5 kVA. Capacity options are available in the 50–100 Newton range to accommodate various testing requirements.

Advantages

Technical Advantages

  • High-precision force and displacement measurement

  • Wide speed range with force-controlled loading capability

  • User-friendly touchscreen interface

  • Automatic stop and rapid return functions

Contribution to Quality Control
ASTM D6641 tests conducted with the DVT FU D NU Universal Testing Machine deliver repeatable and comparable results, supporting consistent quality control in production processes and reducing the risk of defective products.

Support for Export and Certification
Compliance with ASTM D6641 enables preparation of internationally accepted test reports. This facilitates certification procedures and strengthens the competitiveness of products in global markets.

Fields of Application

CLC compression testing using the DVT FU D NU Universal Testing Machine is widely applied by metal manufacturers, wire and pipe producers, conveyor manufacturers, laboratories, and rope manufacturers. In addition to composite materials, the system is commonly used in automotive and sub-industries, construction materials, forestry products, and rubber-based applications.

Tests That Can Be Performed

The system supports a wide range of mechanical tests, including opening/closing, tensile failure, tearing, compression, crushing, elongation, permanent deformation, puncture, and bending tests. This versatility allows both standard-specific and general material testing within a single platform.

Test Specimens

Typical test specimens include aluminum, copper, steel, iron; sheet profiles and springs; cables and steel wires; plastic products; jute materials, slings, jumbo bags, safety belts; adhesives; rubber materials, conveyor belts, and composite structures.

Optional Accessories

Optional equipment such as various jaw designs, specially developed software, computer and printer connections, additional fixtures for special tests, extensometers, temperature-controlled environmental chambers, metal or plexiglass safety enclosures, and light barrier systems further expand the capabilities of the DVT FU D NU Universal Testing Machine.

Standards

ASTM D6641
This standard defines the determination of compressive properties of fiber-reinforced polymer composites under combined loading conditions. It specifies specimen geometry, loading procedures, and measurement requirements to ensure reliable and comparable test results.

Conclusion

The ASTM D6641 Combined Loading Compression Test Method is a highly effective standard for accurately evaluating the compressive performance of composite materials. When implemented using the DVT FU D NU Universal Testing Machine, the method delivers high precision, safety, and versatility, making it suitable for both laboratory and industrial environments. This integrated approach strengthens quality control processes and ensures that engineering decisions are based on reliable mechanical data.