In our institute single-fiber model composites (see below for a scheme) are needed for different experiments, namely quasistatic pull-out tests, high-speed pull-out tests, hysteresis and long-term loading tests and subcritical dynamic loading tests. The fibers have to be embedded at one end to a specific matrix. For sample preparation three work stations with one movable optical system have been set up. Every station allows the melting of the matrix material, the precise positioning of the fiber above the matrix, the actual embedding process and the subsequent cooling according to a defined temperature pattern. During the embedding process, the fibers are held by a gentle pneumatic fiber holder in order to prevent them from damage. The three work stations are mounted on an optical bench. The optical system can be positioned by linear guides to each preparation chamber which allows the embedding of three fibers in parallel. The optical system consists of two components. A camera with long distance optics allows the monitoring of the xy-positioning of the fiber above the matrix. The adjustment of the xy-positioning is carried out manually with a cross table. A second camera monitors the z-coordinate of the fiber that can be adjusted by a micro-drive. Melting, embedding, cooling process and protective gas flushing of the preparation chambers are controlled by a PC.
Fiber material: Glass, carbon, aramid
Fiber diameter: 7 - 30 µm
Embedding length: 50 - 2000 µm
Embedding speed: 6 - 1500 µm/min with 0.1 µm accuracy
Melting temperature: Up to 400°C with 1 K accuracy
Heating rate: Approx. 10 K/s
Control software: Custom-made TestPoint application