  The Hot Slumping Technology is under development by several research groups
in the world for the realization of grazing-incidence segmented mirrors for
X-ray astronomy, based on thin glass plates shaped over a mould at temperatures
above the transformation point. The performed thermal cycle and related
operations might have effects on the strength characteristics of the glass,
with consequences on the structural design of the elemental optical modules and
consecutively on the entire X-ray optic for large astronomical missions like
IXO and ATHENA. The mechanical strength of glass plates after they underwent
the slumping process was tested through destructive double-ring tests in the
context of a study performed by the Astronomical Observatory of Brera with the
collaboration of Stazione Sperimentale del Vetro and BCV Progetti. The entire
study has been realized on more than 200 D263 Schott borosilicate glass
specimens of dimension 100 mm x 100 mm and thickness 0.4 mm, either flat or
bent at a Radius of Curvature of 1000 mm through the particular pressure
assisted hot slumping process developed by INAF-OAB. The collected experimental
data have been compared to non-linear FEM analyses and treated with Weibull
statistic to assess the current IXO glass X-ray telescope design, in terms of
survival probability, when subject to static and acoustic loads characteristic
of the launch phase. The paper describes the activities performed and presents
the obtained results.
