Tests on fiber composites are described in international and national standards (ISO, ASTM, EN, DIN) and in Airbus (AITM) and Boeing (BSS) company standards. In addition, laminates are usually also characterized with the actual dimensions of the eventual components. In aircraft manufacture this results in test specimens with very large dimensions which call for correspondingly high test loads.
One example of this is Airbus Standard AITM 1-008, which describes compression tests up to 500kN for A3 specimens. With such tests in mind Zwick has modified hydraulic tensile grips to enable them to be used for compression tests also. The grips feature sturdy longitudinal guides, while the jaws are equipped for 'soft load introduction'. As well load application via clamping (shear loading), combined loading is also possible, whereby the specimen is additionally held at the ends. During alignment measurements in accordance with Nadcap AC 7122 it was possible to verify the exact alignment of the grips. Verification of compliance with regard to the transverse movement under load as per AITM 1.0008 presented no difficulty with this test assembly.
The use throughout of a modular connection system allows this 600kN testing machine to be reconfigured for a wide range of tests in a very short time. When the machine is fully equipped there are fixtures and sensors available for 21 different types of test, to around 115 standards. In addition to the usual tensile tests these include FHT, OHT, end-loading compression tests, FHC, OHC, overlapping shear, Iosipescu shear, V-notch shear, IPS, SBS and ILSS, three and four-point flexure tests and fracture mechanics investigations.
The makroXtens digital extensometer provides a high-resolution displacement-measurement system which, in addition to tensile tests, can also be used for flexure tests and end-loading compression tests by means of suitable sensor arms.
The temperature chamber is mounted on slide rails for easy insertion and enables tests to be performed over a wide temperature range. Cooling is via liquid nitrogen or a cooling unit as required.
Zwick has additional modular testing systems for testing fiber composites at load levels 100kN and 250kN.