An Introduction to ASTM D695-15
Determining the Compressive Properties of Rigid Plastics
Standard At A Glance
- ASTM D695
Written by Daniel Caesar
ASTM D695 is a test method used to determine the compressive properties of un-reinforced and reinforced plastics. It is used alongside its tensile test standard equivalent, ASTM D638. Together, ASTM D695 and ASTM D638 assess the fundamental material properties of polymers that are found in every industry and even every household around the globe. In order to fully understand the test setup, procedure, and results requirements, it is important to review the full standard.
What Does this Standard Measure?
ASTM D695 obtains the properties of a material's compressive strength, compressive yield point, and modulus. The standard specimen for strength determination is a right cylinder or prism whose length is twice its principal width or diameter. If the specimen is too thin, an anti-buckling support jig should be used to prevent the specimen from buckling.
Materials Testing System
ASTM D695 Test Setup
1. Instron 3400
2. Bluehill Universal Dashboard (2490-696)
3. 2530 Series Load Cell
4. 2501 Series Compression Platens
Platens and Accessories
Depending on your application, the following accessories are commonly used for ASTM D695 testing:
- upper compression platen with integral spherical seat (diameters vary from 2" to 8”)
- lower rigid platen of matching size
- 2601-04X series LVDT (linear displacement transducer)
- LVDT mount for platens (2601-071)
Beyond the typical ASTM E4 verification to ensure accurate force data, D695 also requires an ASTM E83 Class B-2 extensometer to measure compressive strain. A popular strain solution is Instron's linear displacement transducer. A more advanced strain solution includes a non-contacting extensometer, such as Instron's Advanced Video Extensometer 2 (AVE 2). The AVE2 is ideal for labs with limited test systems needing to perform a wide variety of tests.
ASTM D695 Accessories
1.Self-Aligning Spherical Seat
2.Anti-Buckling Support Jig
3. 2601-04X series LVDT
Helpful Tips and Tricks
- Compression platens with integral spherical seats are ideal for ensuring platen to platen parallelism, which is a requirement of the standard.
- If the specimen is too thin, an anti-buckling support jig should be used to prevent the specimen from buckling.
- If reporting the modulus calculation, make sure the extensometer and load cell are both verified in the range that the calculation is being made. Labs sometimes unknowingly report calculations outside of the verified range of their devices.
- ASTM D695 is included in the Plastics test method suite available in Bluehill Universal.
- If direct strain measurement and conformance to ASTM E83 Class B-2 is not required, compliance correction should be used to remove the system’s compliance from the crosshead displacement data. Please review the compliance correction whitepaper for more details.
Instron 6800 Series Universal Testing Systems provide unparalleled accuracy and reliability. Built on a patent-pending Operator Protect system architecture with an all-new Smart-Close Air Kit and Collision Mitigation features, the 6800 Series makes materials testing simpler, smarter, and safer than ever before.
Bluehill Universal Software is built from the ground-up for touch interaction and an intuitive user experience. Discover simpler and smarter testing with features such as pre-loaded test methods, QuickTest in seconds, enhanced data exporting: and Instron Connect – a new feature that provides a direct communication link to Service. Users of previous versions of software such as Bluehill 2 and Bluehill 3 can easily upgrade to the newest version of Bluehill.
This anti-buckling fixture is designed for compression testing of rigid plastics and the shear testing of reinforced plastics. It has also been adapted for use with high strength composites.
The second generation Advanced Video Extensometer (AVE 2) utilizes patented measurement technology in the fastest, most accurate non-contacting strain measurement device commercially available.
These easy-to-install compression platens are precisely machined fixtures that are designed for even distribution of compression loads during a test. The compression load string comprising an upper platen with integral spherical seat and lower rigid platen is attached to the loading axis of the universal testing machine.