High-Temperature Universal Testing Machine

• Subject Area: Materials Engineering
• Term: Funded in 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428091604

The proposed 50 kN High-Temperature-Universal Testing Machine is a unique device, which is specifically designed, in order to test, analyse and study the thermomechanical properties of fiber reinforced ceramic matrix composites. Tensile-, flexural- and pressure-tests can be conducted from room temperature up to 1500 °C in air and flushing inert gases. In order to fulfil these challenging tasks, the device is equipped with two different furnaces. The first furnace consists of a long, split-tube furnace (diameter 100 mm) with temperatures up to 1550 °C. The second one, a short split furnace (85 mm height), is capable to test samples up to 1400 °C. Within the long, tube furnace tensile-, flexural- and pressure-tests are possible up to 1500 °C in air and in flushing gases, e.g. nitrogen or argon.The rod system of the load train is designed for the testing of brittle ceramic materials, by a spherical bearing and consists of SiC, which enables these high testing temperatures. The load train, the sample clamps and the sample itself is located in the hot region of the long, tube furnaces, which means a hot environment. Therefore, the maximum applicable temperature decreases to about 2 kN at 1400 °C.As an alternative approach, within the short split furnace, tensile tests are possible up to 1400 °C with 50 kN, because the sample clamps and fixtures are placed outside of the short furnace at moderate temperatures < 250 °C. This special setup enables the application of a metallic load train and the maximum force (50 kN) for CMC tensile samples and their fixation outside of the furnace in a "cold" environment.Additionally, due to the lower furnace volume, it is possible to save time. High temperature tests, run about three times faster, which increases the number of high temperatures tests per day. Another advantage of the short split furnace is the use of conventional sample fixtures, which are used at room temperature up to moderate temperatures. Therefore, even for testing and fixation of high performance fibers resp. ceramic fibers the short furnace is suitable up to 1400 °C.In order to find a suitable load transfer from the sample grips towards the ceramic samples, a specific shoulder loaded gripping setup is designed, which can be supported by face loading grips. Due to this setup, torsional- and flexural-moments can be prevented during the tensile tests. Finally, the strain measurement system should be mentioned, which is unique, like the complete universal testing machine. In order to prevent contact of strain measurement gages with the samples a contactless system, which consists of a laser-speckle-extensometer was chosen. This extensometer enable strain-speed controlled tests and do not need any marks on the surface of the samples. For flexural and pressure tests, the laser extensometer is partially suitable and will be supported by a Linear Variable Differential Transformer. For room temperature tests, a video extensometer is applicable.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Hochtemperatur-Universalprüfgerät
• Instrumentation Group: 2900 Statische und quasistatische Prüfmaschinen und -anlagen
• Applicant Institution: Universität Bayreuth
• Leaders: Professor Dr.-Ing. Walter Krenkel, from 6/2019 until 2/2021; Professor Dr.-Ing. Stefan Schafföner