Strain Measurement on the Glass-Fiber Reinforced Plastic by Using Optical Measurement System

Abstract

This paper deals with experimental determination of the mechanical properties of the fiber glass-reinforced plastic. Nine test samples were made from fiber-glass plastic, where three series with three samples each were with different thickness. All samples were of nominal length 250 mm with fibers of length 50 mm. The width of the specimens was 25 mm, and the thickness was 0,35 mm; 0,8 mm and 1,16 mm, respectively. The samples were subjected to tensile testing on a tensile machine in order to determine the mechanical properties. The force and longitudinal displacement (actuator displacement) were measured on the tensile testing machine, while with the optical measuring system, strains in the transverse direction (perpendicular to the tensioning direction) were measured. The results of the measurements on the tensile test machine, presented in the form of stress-displacement diagrams, are shown first within the same series (equal thickness of the test sample) and then the results are compared for different thicknesses of the test sample. By tensometric measurements, the change of the principal strains over time was determined. The engineering stress-strain curve for all nine test specimens was obtained using the optical measuring system and given in form of diagrams. It was found that the best tensile properties of all considered specimens have test specimens with the largest thickness, which also had glass fibers of knitted structure.

Keywords

• fiberglass plastic
• mechanical properties
• optical measuring system
• strain measurement