IWPDF2023

Fixture for 2D Compression Test with Uniaxial Testing Machine

V.A. Kolupaev ∗

Mechanics & Simulation, Department of Plastics, Fraunhofer Institute for Structural Durability and System Reliability (LBF), Schloßgartenstr. 6, D-64289 Darmstadt, Germany

∗ vladimir.kolupaev@lbf.fraunhofer.de

Keywords: Design, Equibiaxial compression, Optimization

2D compression test is essential for design of critical parts. Equibiaxial compression test can be easily performed using a circumferential clamp (Figure 1). The load F is applied using a uniaxial testing machine. The eccentricity e x is utilized to obtain uniform stress distribution. The gap e y is estimated from the uniaxial compression test data. Specimen "biting" at the overhang area of the gap is minimized with a compensator. Friction is reduced by lubricating the contact area. Partially overlapping curved sheets can be placed in the contact area.

Figure 1: 2D compression test: 1 - compression clamp, 2 - specimen, 3 - compensator.

When designing the fixture with FEM, the optimization objectives include the following:

• simultaneous plastification of the clamp in the entire contact area and

• equal change of the inner radii of the clamp ∆ at the selected angles φ during loading.

The recommended thickness of a metal or polymer foam specimen is b = d/ 2 . For the testing of sheet specimens made e.g., of fiber-reinforced polymers, a groove is provided on the grips in the contact area to ensure specimen fixation and stability during loading. The depth of the groove is matched to the thickness of the specimen. The clamp material is plasticized during the test. The reuse of the clamp after the test with subsequent mechanical treatment is under discussion.

The specimen is speckled with a statistically distributed black & white pattern. This allows the two-dimensional strain on the specimen surface to be evaluated by digital image correlation as

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