Application of Serial Sectioning to Evaluate the Performance of x-ray Computed Tomography for Quantitative Porosity Measurements in Additively Manufactured Metals

Voids are a concern in composite materials, as they may have a negative effect on the mechanical properties of the laminates. Voids may develop especially in low cost or off-optimum process conditions. In this study, samples of glass reinforced epoxy laminates with void volume fractions in the 0.5–7% range were successfully obtained by varying the vacuum in the hand layup vacuum bagging manufacturing process. Void content was experimentally characterized using four different methods: ultrasonic scanning, epoxy burn off, serial sectioning, and X-ray computed tomography. The goal of this paper was to determine how the methods compared with respect to each other at quantifying void content. The specimens were taken from nearby locations in the same panels, so a true comparison of the methods could be obtained. The results showed, for the specific material and manufacturing conditions used, that the four different techniques can quantify voids content but with a large variation in the accuracy. X-ray computed tomography was the most successful technique to characterize voids, followed by serial sectioning. Ultrasonic scanning and epoxy burn off were not recommended techniques to characterize voids for laminates manufactured with these materials and process conditions. However, epoxy burn off was a successful technique to calculate fiber and resin weight fraction.

Download Full-text

Porosity measurements by X-ray computed tomography: Accuracy evaluation using a calibrated object

Precision Engineering ◽

10.1016/j.precisioneng.2017.03.007 ◽

2017 ◽

Vol 49 ◽

pp. 377-387 ◽

Cited By ~ 28

Author(s):

Petr Hermanek ◽

Simone Carmignato

Keyword(s):

Computed Tomography ◽

Accuracy Evaluation ◽

X Ray ◽

X Ray Computed ◽

Porosity Measurements

Download Full-text

High-resolution imaging of depth filter structures using X-ray computed tomography

Journal of Materials Science ◽

10.1007/s10853-021-06238-w ◽

2021 ◽

Author(s):

T. F. Johnson ◽

F. Iacoviello ◽

J. H. Welsh ◽

P. R. Shearing ◽

D. G. Bracewell

Keyword(s):

Computed Tomography ◽

Flow Simulation ◽

Pixel Size ◽

Average Pore ◽

X Ray ◽

Average Porosity ◽

X Ray Computed ◽

Resolution Imaging ◽

Filter Structures ◽

Porosity Measurements

AbstractA multiple length scale approach to the imaging and measurement of depth filters using X-ray computed tomography is described. Three different filter grades of varying nominal retention ratings were visualized in 3D and compared quantitatively based on porosity, pore size and tortuosity. Positional based analysis within the filters revealed greater voidage and average pore sizes in the upstream quartile before reducing progressively through the filter from the center to the downstream quartile, with these results visually supported by voidage distance maps in each case. Flow simulation to display tortuous paths that flow may take through internal voidage were examined.Digital reconstructions were capable of identifying individual constituents of voidage, cellulose and perlite inside each depth filter grade, with elemental analysis on upstream and downstream surfaces confirming perlite presence. Achieving an appropriate pixel size was of particular importance when optimizing imaging conditions for all grades examined. A 3 µm pixel size was capable of representing internal macropores of each filter structure; however, for the finest grade, an improvement to a 1 µm pixel size was required in order to resolve micropores and small perlite shards. Enhancing the pixel size resulted in average porosity measurements of 70% to 80% for all grades. Graphical abstract

Download Full-text

High-resolution imaging of depth filter structures using X-ray computed tomography

10.22541/au.161047659.97113522/v1 ◽

2021 ◽

Author(s):

Thomas Johnson ◽

Francesco Iacoviello ◽

John Welsh ◽

Paul Shearing ◽

Daniel Bracewell

Keyword(s):

Computed Tomography ◽

Flow Simulation ◽

Pixel Size ◽

Average Pore ◽

X Ray ◽

Average Porosity ◽

X Ray Computed ◽

Resolution Imaging ◽

Filter Structures ◽

Porosity Measurements

A multiple length scale approach to the imaging and measurement of depth filters using X-ray computed tomography is described. Three different filter grades of varying nominal retention ratings were visualized in 3D and compared quantitatively based on porosity, pore size and tortuosity. Positional based analysis within the filters revealed greater voidage and larger average pore sizes in the upstream quartile before reducing progressively through the filter from the center to the downstream quartile, with these results visually supported by voidage distance maps in each case. Flow simulation to display tortuous paths that flow may take through internal voidage were examined. Digital reconstructions were capable of identifying individual constituents of voidage, cellulose and perlite inside each depth filter grade, with elemental analysis on upstream and downstream surfaces confirming perlite presence. Achieving an appropriate pixel size was of particular importance when optimizing imaging conditions for all grades examined. A 3 µm pixel size was capable of representing internal macropores of each filter structure, however for the finest grade an improvement to a 1 µm pixel size was required in order to resolve micropores and small perlite shards. Enhancing pixel size resulted in average porosity measurements of 70% to 80% for all grades.

Download Full-text