Adapted buckling support to investigate the compressive properties of long and thin specimen

Kötter, Benedikt
Mittelhaus, Janina
Körbelin, Johann
Fiedler, Bodo
When fibre reinforced polymers (FRPs) are used as load-bearing structural materials, the designer cannot always prevent compressive stresses from occurring in the material. If compressive loads occur, these often determine the dimensioning of the component, since the compressive strength of FRP is significantly lower than the tensile strength. This circumstance makes it particularly important to know the compressive strength of FRP exactly and to determine it experimentally as precisely as possible. The work carried out here has investigated a relatively new test device with combined load application for the failure of FRP under compressive load. For tensile-compressive tests (R=-0.5), the Instron 8800H2470 under stress control mode at 5 Hz with a maximum force of 100 kN and the Instron 8802L2741 under stress control mode at 3 Hz with a maximum force of 250 kN were used. For fixing servo-hydraulic clamps with a hydraulic pressure of 120 bar clamped the specimens. Anti- buckling supports were employed during the tests to prevent buckling of the samples and premature failure. The anti-buckling support designed for fatigue after impact tests was used. This design is similar to the device used in the open hole compressive tests (ASTM D6484-04 [3]), with the difference that the load is applied via shear forces. The advantage of the anti-buckling support is that the specimen is supported along its entire length, reducing the probability of local buckling. The samples are not restrained laterally, so transverse contraction is not restricted. This design can reduce or avoid stress concentrations at the edges of the specimen ​
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