Weibull analysis of the mechanical strength of silica gels

Since gels are typically brittle materials, reliable analyses are essential to determine the strength distribution. The mechanical strength of silica gels has been measured by the three point bending technique. Based on the Weibull function, the statistical analysis allows determination of the Weibull modulus (m), which characterizes the strength distribution and the flaw size effect.Two kinds of gels, alcogels and aerogels, have been investigated with respect to their different mechanical behaviour owing to the transformations occurring during the supercritical drying (SD). The toughness of the two materials has been also measured by the SENB technique. It appears that the strength increases by a factor greater than two during SD, the K_IC increases slightly. However, m is not greatly affected which would suggest that SD does not induce significant flaws or defects change in the network.