## 3 Results and Discussions
### Statistical Analysis of the Pore Characteristics  
The purpose of this subparagraph is to determine the distribution of the pores and to analyze the pore sizes, pore number, and pore shapes. The results of the statistical analysis of panel 1 are presented below, while panels 2 and 3 are seen to follow similar trends.  
The 3D distributions of the pores for all five samples of panel 1 are shown in Figure 13. A single point within coordinates X, Y, and Z (Figure 13) represents the center of the circumscribed sphere of the closed pores. The pore distribution is homogeneous across all analyzed samples, with no pore agglomerations on the surface.  
Figure 12: (**a**) The interval plot of the panel porosity for composite 1. (**b**) The interval plot of the panel porosity for composite 2. (**c**) The interval plot of the panel density. Bars are one standard error from the mean. Individual standard deviations were used to calculate the intervals.  
The scatter plots of the pores, as well as the distributions in two dimensions using histograms, are shown in Figure 14a-c. The scatter plots show a homogeneous distribution of the pore volume on the X, Y, and Z axes. The distribution has a volume cluster between 0.01 and 0.1 mm\({}^{3}\). Outliers indicate a singular pore volume greater than 0.1 mm\({}^{3}\). Similar distributions of pore volume versus X, Y, and Z coordinates were found for all the samples.  
Figure 13: The 3D distribution of the pores x, y, and z are the coordinates of the circumscribed sphere center of the pore: (**a**) sample S1; (**b**) sample S2; (**c**) sample S3; (**d**) sample S4; (**e**) sample S5.  
The bar chart (Figure 14d) shows the most common volume size of the closed pores, the number of pores (NP\({}_{\text{multi},\text{mat}}\)), and percentages of multi-material. The values are arranged in size from largest to smallest. The most frequently occurring closed pores detected have a volume of around 0.01-0.02 mm\({}^{3}\). Similar pore volume distributions were detected across all samples. Using the volume size detected within all samples, the closed pores were classified into four classes of size: 0.01-0.02, 0.02-0.05, 0.05-0.09, and 0.09-1.33 mm\({}^{3}\).  
The graphs from Figure 15a-c show the interval plots of the diameter, surface, and the number of closed pores versus pore volume classes for panel 1. Individual standard deviations were then used to calculate the intervals plot.  
The shape of the pores was characterized based on the sphericity (Sp) parameter [33]. The sphericity parameter of pores is calculated based on Equation (1). The parameters involved in Equation (1) are the volume (V) and the surface area (A) of the pore [34].  
\[S_{p}=6\sqrt{\pi}\frac{V}{\sqrt{A^{3}}} \tag{1}\]  
The relationship between sphericity vs. pore volume (Figure 16) shows three closed-pore shapes:  
* Few pores having a regular shape (Sp \(>\) 0.5);
* Most of the pores having an irregular shape (0.2 \(<\) Sp \(<\) 0.5);
* Very few pores having an elongated shape (Sp \(<\) 0.2).  
Figure 14: Closed pore volume distribution of sample S1: (**a**) versus X; (**b**) versus Y; (**c**) versus Z; (**d**) the number of pores versus pore volume.