Void Content Determination of Carbon Fiber Reinforced Polymers: A Comparison between Destructive and Non-Destructive Methods

Abstract

The properties of composite materials are highly dependent on the fiber and matrix fraction and on the porosity resulting from micro voids. This paper addresses void content characterization and the constituent content of composite materials by resorting to a comparison of destructive and non-destructive methods. The work presents the detailed procedures of two destructive methods, using acid digestion of epoxy resins matrices, and compares their processes. It also presents the results of a non-destructive method, by means of Micro Computed Tomography (MicroCT). The results of both destructive and non-destructive methods are compared, and a recommendation is made based on the application and the type of composite being analyzed. The MicroCT showed better and more consistent results in detecting voids in the material, while the acid digestion tests provided better results about the fiber and matrix percentage. Exported results from the MicroCT scanning with actual locations of voids were used in numerical analysis, to examine the feasibility of using them, whether by developing models that map damage in the proximity of the void, or by developing models that predict the properties of the entire material with respect to the content, shape, and distribution in the material.

Design and Testing of a Composite Pressure Hull for Deep Autonomous Underwater Vehicles

“…The results of the void determination tests of the different samples showed that the void content is less than 2%, the percentage recommended by [15]. The void content according to the non-destructive testing was 1.531%, and the Fiber/Matrix ratio according to the destructive one was 57.6 / 41.1 [37]. Judging by the results, the manufacturing facilities were deemed safe for the next phase, and the quality of the product will be according to standards.…”

“…Figure 8 shows some of the practical results of the two tests. A detailed description of the tests and the tests procedures has been described in previous work [37]. The results of the void determination tests of the different samples showed that the void content is less than 2%, the percentage recommended by [15].…”

“…Figure 8 Example of the results of the micro voids tests; (a) fibers remaining after the itching process of the acid digestion tests, (b) reconstructed image resulting from the MicroCT scanning, showing the voids in red and the material in grey[37] …”

Design and testing of a composite pressure hull for deep autonomous underwater vehicles.

“…The results of the void determination tests of the different samples indicated that the content being less than 2%, the percentage recommended by Mallick [17]. The void content according to the non-destructive testing was 1.531%, and the Fiber/Matrix ratio according to the destructive one was 57.6 / 41.1 [39]. Judging by the results, the manufacturing facilities were deemed safe for the next phase, and the quality of the product will be in line with standards.…”

“…Figure 8 shows some of the practical results of the two tests. A detailed description of the tests and the tests procedures has been reported in previous work [39].…”