| BS EN ISO: 527 | Part: 5 | Published: 1997 | Contact: BSI |
| Title | Plastics - Determination of tensile properties - Test conditions for unidirectional fibre reinforced plastic composites |
| Scope | This part of ISO specifies the test conditions for the determination of the tensile properties of unidirectional fibre-reinforced plastic composites, based upon the general principles given in part 1. |
| Comment | Inputs were included mainly from ASTM D3039, JIS 7073, CRAG 300, EN 61 and EN aerospace methods (2561, 2597 and 2747). EN ISO 527 Part 5 [19] was parallel voted as a CEN standard and should, with Part 4, replace EN61 and possibly in time the material specific Aerospace EN standards. The specimen sizes agreed during the harmonisation of this test for Part 5 are 250 mm x 15 mm x 1 mm in the 0° direction (parallel to fibre axis) and 250 mm x 25 mm x 2 mm in the 90° direction. These sizes are now the same for all series except EN Aerospace for glass-fibre systems (EN 2747).Several other aspects of the test method were decided during the drafting of the new standard following agreement on the specimen sizes. For example, a glass-fibre fabric/epoxy, aligned at ±45° to the specimen axis, was chosen as the preferred tabbing material, but alternatives were allowed providing it was shown that the strength was at least equal to that obtained with the preferred tab material and that there was no increase in scatter. A tab angle of 90° was adopted as in EN 2561 and CRAG (3rd edition), with additional, indirect, support from Japanese round-robin (RR) results, which was inconclusive regarding the preferred tab angle. The remaining differences between various versions of the tensile test to be tackled in the next revisions are given the ""Introduction to testing""The modulus is calculated as the chord value between 0.0005 (=0.05%) and 0.0025 (=0.25%) strain to agree with Part 1 of ISO 527. However, the EN Aerospace series still uses a load based criteria to determine the modulus (ie between 0.1 and 0.5 of the maximum load).Particularly when testing aligned materials in the fibre direction, it is necessary to use the minimum grip pressure to avoid slippage as otherwise crushing of the specimen within the grips can occur due to the low through-thickness and transverse strength, compared to the axial strength. This also applies to a lesser degree to other composite materials. A particular feature of Parts 4 and 5 for composites is that an informative annex has been added recommending an alignment check to be undertaken due to low failure strains involved, particularly for the 90° specimen of fully aligned materials.Test equipment requirements mainly relate to the need for a tensile capacity of 100 to 200 kN to test the higher performance laminates. For strain measurements clip gauge extensometers are commonly used, being more economical than strain gauges. |
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