Porosity Characterization of Carbon Fiber/Epoxy Composite Using Hg Porosimetry and Other Techniques

Abstract

In polymer composites, the porosity acts mainly as a stress concentrator, which has detrimental effects depending on the shape and position of the voids. Also, the presence of voids is detrimental to the mechanical properties, which results in the need for an accurate method for their characterization in terms of morphology, position, and volume fraction. The aim of this study was to establish an appropriate procedure for the measurement of voids in a polymer composite using the mercury porosimetry technique. Data were also collected using the Taguchi approach. Subsequently, the feasibility of applying the Hg porosimetry methodology was confirmed through a comparison with standard techniques. Statistical analysis was used to determine the best Hg porosimetry parameters and pressures between 203 and 231 MPa was found to generate reliable results for the maximum porosity measurement, with no dependence on other parameters. Since the Hg porosimetry, acid digestion, and optical microscopy methods provided porosity results with a statistically significant similarity, it can be concluded that all these methods are feasible for the analysis of voids. Finally, potential benefits of the proposed porosity analysis methodology were highlighted through the characterization of the void volume, position, and morphology. POLYM. ENG. SCI., 60:841–849, 2020. © 2020 Society of Plastics Engineers

On the 3D void formation of hybrid carbon/glass fiber composite laminates: A statistical approach

“…The single factor methodology with repetition was used for a comparison of the influence of parameters on the response [22]. A normal distribution is also performed to measure the void content distribution for each laminate.…”

“…( 3)) to describe the interaction among the combination of different void fractions in the hybrid composites and the void formation (morphology and position through-thickness and laminate length). This section aims to reduce the number of experiments required for the porosity prediction in different hybrid laminates, ensuring low cost and experimental time and keeping statistical relevance [22,27]. For a better forecast with small error, the maximum, medium, and minimum levels are selected, as explained in the supplementary material.…”

“…In addition, experimental values represented by black dots, evidenced in all SRM graphics, represents the experimental points that control and determine the SRM behavior. The great advantage of this application is the reduction of the experimental number required to void formation prediction in different hybrid laminates ratio [22].…”

“…Even using sophisticated techniques for void measurement (e.g., optical microscopy [20], scanning electron microscopy [21], and microscopic computed tomography [17]), its data variation is challenging given the lack of post-processing method to take all effects into account. For reliable analyzes of the measurements, statistical approaches are a feasible way to describe porosity formation since it can reduce the variation according to the reliability level and analyze the variance meaningfully [22,23] instead of merely using deterministic methodologies.…”

Porosity characterization and respective influence on short-beam strength of advanced composite processed by resin transfer molding and compression molding

“…Its acceptance for structural application is usually around 2%, and it can be generated by air trapped in the system before or during manufacturing or when there is a macro-impregnation occurring before micro-impregnation, that is, the spaces between tows are filled but not the spaces between tow filaments. 13–16 Several authors testify that higher void content conducts to a decrease in the mechanical performance of the part. 17–19…”