Measurement of Three Dimensional Fiber Orientation Distribution in Fiber Reinforced Thermoplastics Using Scanning Acoustic Microscopy

Abstract

Measurement of fiber orientation is an important inspection item to examine the shape and strength of products. Fiber orientation has been measured from photographs of thinly sliced FRP or by observation of the orientational behavior of maker fibers. However, only two dimensional fiber orientation is obtained with photographs. In recent years, the measurement of three-dimensional fiber orientation using scanning electric microscopy has been reported. However, research data on three-dimensional orientation distributions is insufficient. We report on a method of measuring the three-dimensional fiber orientation using the scanning acoustic microscope.
The method to we propose involves visualizing the interference fringes along the fibers, and calculating three-dimensional fiber orientation of parameters from these interference fringes. Finally, the distribution of fiber orientations is measured at each position. A merit of the method that we propose is the lack of ambiguity in comparison with a method using elliptical marks on sectioned polished surfaces and this method is not influenced by noise patterns.
The following results were obtained:
(1) We were able to measure the three-dimensional fiber orientation non-destructively.
(2) Using a test pattern, the measured orientation parameters almost agree with the theoretical parameters.
(3) For test specimens with uneven surface, we confirmed the vertical distribution of the fiber orientation in the concave position of the surface.
We were thus able to confirm the validity of the proposed method by experiments.