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Short answer
ASTM D695 is the ASTM test method for the compressive properties of rigid plastics, including high-modulus composites. It covers unreinforced and reinforced materials loaded in compression at relatively low, uniform rates, using specimens of standard shape. It yields modulus of elasticity, yield stress, deformation beyond yield and compressive strength, as test-condition data rather than design data.
Definition and scope
ASTM D695, “Standard Test Method for Compressive Properties of Rigid Plastics”, is issued by ASTM International. The current edition on the ASTM store listing is D695-26 (status Active, last updated 2 February 2026; DOI 10.1520/D0695-26). Section 1.1 states that it covers the mechanical properties of unreinforced and reinforced rigid plastics, including high-modulus composites, when loaded in compression at relatively low uniform rates of straining or loading, and that it is applicable for a composite modulus up to and including 41,370 MPa (6,000,000 psi). SI values are the standard (section 1.2). The scope also states that the user is responsible for establishing safety, health and environmental practices (section 1.3).
How it is used in practice
Intertek’s test-method summary describes the arrangement in general terms: a specimen is compressed between plates at a uniform rate, the maximum load is recorded along with stress-strain data, and an extensometer is used to determine modulus. It defines compressive strength as the maximum compressive load divided by the minimum cross-sectional area, and compressive modulus as the change in stress divided by the change in strain. ASTM’s own text says the data are useful for research and development, quality control, acceptance or rejection under specifications, and special purposes (section 5.3).
The properties D695 can report are listed in section 5.2: modulus of elasticity, yield stress, deformation beyond the yield point, and compressive strength (unless the material merely flattens but does not fracture). Test conditions such as specimen preparation, conditioning, dimensions and test parameters are governed first by the ASTM specification for the material being tested; section 5.4 states that the materials specification takes precedence over the defaults in D695, and points to Table 1 of Classification D4000, which lists the existing ASTM materials standards.
D695 and ISO 604: related standards, different preferred specimens
ASTM states in Note 2 of D695 that the standard is equivalent to ISO 604. The two do not prefer the same specimen, according to Intertek’s summary:
| Item | ASTM D695 (typical) | ISO 604 (preferred) |
|---|---|---|
| Typical or preferred shapes | Blocks 12.7 × 12.7 × 25.4 mm (½ × ½ × 1 in) or cylinders 12.7 mm (½ in) in diameter and 25.4 mm (1 in) long | See the two rows below |
| Specimen for modulus | Block or cylinder as above | 50 × 10 × 4 mm |
| Specimen for strength | Block or cylinder as above | 10 × 10 × 4 mm |
Source for the table: Intertek Testlopedia, “Compression Properties ASTM D695, ISO 604”, checked 29 October 2026. A report that cites one standard therefore should not be assumed to describe specimens that meet the other.
When D695 is not the right test
- Resin-matrix composites with oriented continuous, discontinuous or cross-ply reinforcement: Note 1 of D695 says tests may be made in accordance with D3410/D3410M or D6641/D6641M instead.
- Applications whose load-time scale differs widely from the standard test: section 5.3 says the results cannot be considered significant for engineering design there, and that such applications require additional tests such as impact, creep and fatigue.
- Tensile behavior: that is a different property set; see the CASRAI guide to ASTM D638 tensile properties of plastics.
Where it matters for labs and supply decisions: reading a D695 result
Each point below traces to the ASTM text cited above. When a laboratory or a supplier quotes a D695 value, check:
- Edition. The active edition is D695-26. A report citing an earlier edition, such as D695-02, reflects that edition’s text.
- Governing material specification. If an ASTM material specification exists for the plastic, its specimen preparation, conditioning, dimensions and test parameters take precedence (5.4). Table 1 of D4000 lists those specifications.
- Which property is reported. Modulus, yield stress, deformation beyond yield and compressive strength are different quantities (5.2). A single “compressive strength” figure alone does not carry the others.
- Whether the material fractured. Where a material does not fail by a shattering fracture, the compressive strength is arbitrary, depending on the degree of distortion regarded as complete failure; for materials that flatten into a disk without fracture, ASTM says compressive strength “can have no real meaning” (5.2).
- Specimen shape. Block or cylinder, and the dimensions, since the ISO route prefers different specimens.
For how a laboratory documents methods like this internally, see standard operating procedure (SOP). For selecting plastics in wetted equipment, a separate question from mechanical compression data, see the chemical compatibility chart for wetted materials.
Common misunderstandings
- “A D695 value is a design allowable.” ASTM section 5.3 says the tests cannot be considered significant for engineering design in applications differing widely from the load-time scale of the standard test.
- “Every material has a yield point.” Section 5.2 notes that materials with a low order of ductility may not exhibit one.
- “The default specimen always applies.” The material specification takes precedence where one exists (5.4).
- “D695 and ISO 604 are interchangeable on paper.” They are equivalent per ASTM Note 2, but the specimens each prefers differ.
FAQ
What does ASTM D695 measure?
Compressive properties of rigid plastics: modulus of elasticity, yield stress, deformation beyond the yield point and compressive strength, where the material fractures.
Is ASTM D695 the same as ISO 604?
ASTM describes D695 as equivalent to ISO 604 (Note 2). Intertek’s summary lists different preferred specimen sizes for each.
Which edition is current?
The ASTM store listing shows D695-26 as Active, last updated 2 February 2026, as checked on 29 October 2026.
What upper modulus does D695 cover?
Composite modulus up to and including 41,370 MPa (6,000,000 psi), per section 1.1.
Sources
- ASTM International, D695-26 store listing (scope, significance and use, notes): https://store.astm.org/d0695-26.html, checked 29 October 2026.
- ASTM International, D695-02 store listing (historical edition scope): https://store.astm.org/d0695-02.html, checked 29 October 2026.
- Intertek, Testlopedia, Compression Properties ASTM D695, ISO 604: https://www.intertek.com/polymers-plastics/testlopedia/compression-properties-astm-d695/, checked 29 October 2026. A testing laboratory’s general summary, not ASTM text.
