1. Characterization of commercial soda-lime-silica glasses Andrew Cachiaras Mentored by Dr. Jeffrey Swab
Introduction
Results
Conclusion
Soda-lime-silicate (SLS) float glass is a common component in transparent armor systems because it is readily available and inexpensive. It is necessary to characterize SLS glass produced by different manufacturers to identify differences and similarities in regards to use in transparent armor systems. Three of the United States producers of SLS glass are: Guardian Industries, Pittsburgh Plate Glass, and Saint Gobain. Not much is known about the differences or similarities between the glass produced by these three manufacturers. A statistical analysis will be employed in order to determine and compare selected material properties of the SLS glasses produced by these three manufacturers to identify their potential use in transparent armor systems.
Each of the three elastic moduli measured indicate a resistance to a different type of force. Bulk Modulus can be defined as the plate’s resistance to compression. Shear Modulus is a resistance to shearing, and Young’s Modulus is a resistance to elastic stretching. Average elastic modulus values are shown in Figure 1 with bars indicating one standard deviation. Sixty samples of each type of glass were included in the mean, except for Diamant®, which had only thirty samples, due to time limitations.
When ANOVA statistical tests were performed using computer software, each elastic property returned a p-value of less than This means, with the null hypothesis (H0) that there is no difference between the glasses, there is less than a percent chance of these results occurring randomly. Using a standard significance level of 5 percent, the null hypothesis can clearly be rejected, meaning that the results are due to something other than random variability, and there is a significant difference between plates. The ANOVA testing for flexural strength returned a p-value of 0.86, meaning that there is an eighty-six percent chance that the same data would occur solely due to random chance. The difference in flexural strengths can be attributed to small variances in testing conditions or potential surface flaws due to handling.
The aim of this project was to discern whether or not there is a significant difference in the properties between several SLS glasses manufactured by different US companies. As displayed by the data, there is a fair amount of variation between the plates in all three of the elastic moduli measured. The Starphire® plates had the highest average Bulk Modulus, approximately one gigapascal (GPa) higher than the next closest mean (UltraWhite®). Diamant® had the highest Shear Modulus, as well as the smallest spread of data. Starphire® also had the highest Young’s Modulus, with UltraWhite® being the lowest. It is important to note that, although the Diamant® plates may have had the highest mean flexural strength in this data set, this strength value was not statistically different compared to the other glasses. This study was helpful in showing that the measured properties are relatively similar for all glasses observed.
When all measured properties are considered, the question of which type of glass is the “best” will most likely depend on the application. For example, if the only important thing is raw flexural strength, then the results of this study are not very useful, as it established no significant difference between the strength values of these three types of plates. However, if a combination of all of the elastic moduli is taken into account, it may be said that the Diamant® plates could be considered as a valid option that would perform consistently when compared to these other types of glass.
Materials and Methods
Groups of 60 SLS glass plates from each of the three manufacturers (Starphire® by Pittsburgh Plate Glass, UltraWhite® by Guardian, and Diamant® by Saint Gobain Glass) of dimensions 6” x 6” x 0.25” were tested. Initially, the average thickness of each plate was determined by measuring the thickness at each corner with a micrometer. The length and width of each plate was measured separately with calipers. Afterwards, the plate was weighed using a balance.
Next, a resonant ultrasound spectroscopy (RUS) machine was implemented to assess elastic properties. Although others were collected, the three main elastic properties that were tested in this study were Bulk Modulus, Shear Modulus, and Young’s Modulus.
Finally, the method laid out in the American Society for Testing and Materials (ASTM) C1499 (2013) was followed in order to determine the equibiaxial flexure strength of the tin side of the three glasses. This was done using a Zwick™ universal testing frame, which calculated the total force required to break the plate, then related the total break force to the flexural strength using data previously acquired, such as dimensions and Poisson’s ratio (which was also collected during resonant ultrasound spectroscopy).
Starphire®
UltraWhite®
Diamant®
Legend
Figure 1: Maximum values vary depending on the property, but the Starphire® plates have a much greater spread in data, indicating that it may be a less reliable type of plate. UltraWhite® had generally low mean values for elastic properties, but had a relatively high max value for flexural strength.
References
ASTM C1499. (2013). Standard test method for monotonic equibiaxial flexural strength of advanced ceramic at ambient temperature. ASTM International, West Conshohocken, PA.
Acknowledgements
I would like to thank my mentor, Dr. Swab, for teaching me the many skills involved in this project, and my advisor, Mrs. Gabriel for helping me put all of the pieces together.