Compressive Properties (CLC) ASTM D6641
Understanding ASTM D6641
Compressive strength is an important mechanical property that determines the ability of a material to withstand compressive loads. Polymer matrix composite laminates, which are widely used in aerospace, automotive, and other industries, are often subjected to compressive loads. ASTM D6641 is a widely accepted test method to determine the compressive properties of such laminates.
The ASTM D6641 test method involves applying a combined end-loading and shear-loading to the unsupported center of the test specimen. The test fixture is designed to apply a specific load to a 12 mm (0.5 inch) gauge length of the specimen.
To perform the test, the specimen is inserted into the two halves of the test fixture and tightened with bolts to secure it in place. The fixture is then placed between the platens of a Universal Testing Machine. The specimen is compressed until it fails.
The test yields three important parameters: compressive strength, compressive modulus, and compressive Poisson's ratio by chord method. Compressive strength is calculated by dividing the maximum load by the product of the specimen width and thickness. Compressive modulus is determined by calculating the chord modulus from 0.1% to 0.3% strain. Compressive Poisson's ratio is calculated from 0.1% to 0.3% strain using the chord method.
It is important to note that other ASTM test methods, such as ASTM D3410 and ASTM D695, only consider either shear-loading or end-loading, respectively. However, ASTM D6641 is unique in that it combines both types of loading, providing a more comprehensive assessment of the compressive properties of polymer matrix composite laminates.
An alternative to the standard test method is to perform the ASTM D6641 modified using the Hydraulic Composites Test Fixture (HCCF) for improved reproducibility. The HCCF uses a hydraulic system to apply the compressive load, which helps to minimize friction and improve accuracy. This modification is particularly useful when testing materials with low compressive strength or when testing in environmental conditions where temperature or humidity may affect the results.
In our opinion, the ASTM D6641 test method is an essential tool for determining the compressive properties of polymer matrix composite laminates. It provides valuable information on the material's compressive strength, compressive modulus, and compressive Poisson's ratio, which are important parameters for design and engineering applications. The use of the HCCF modification can further improve the accuracy and reproducibility of the test results.