Strain Measurement at Glass Fibers

U-Träger mit Glasfaser und Markierungen (Mit Widerstand zum Größenvergleich)

Nahaufnahme der Glasfaser mit Kodiermarken. (Faser durch blauen Pfeil markiert)

A laser extensometer P-50 was used for measuring strain at different glass fibers with a diameter of about 10 µm. With each experiment a single fiber was tested. For the experiment the fiber is glued together with a U-shaped carrier. To observe strain, markers made of sticky tape are put on the fiber. The rear side of the markers is covered with paper, to pre-vent sticking to the equipment. During the experi-ment, a black screen is placed behind the fiber to avoid spinning of the markers. The U-shaped carrier is inserted into the grips of the testor. Before starting the experiment, the side part of the carrier is cut open, hence only the fiber is loaded.

Measuring Results

The following two figures depict results of two experiments with different fibers:

The experiments were carried out at a tensile testor with a 500 N load cell. Since the maximum load was only 0.2 N, the force signal was rather noisy. The red curve shows the result of a moving average. The laser extensometer P-50 used for this experiment has a scanning range of 50 mm, a resolution of 0.1 µm and an accuracy class 0.2 (DIN/EN 10002-4). Because of the contact free measuring principle the specimen is neither influenced by the laser extensometer, nor is the measurement falsified by gliding or similar phenomena. The laser extensometer P-50 is especially suited for materials with small deformati-ons like glass fibers, fiber reinforced materials, high-strength steel, concrete and others.