Molding of complex composite parts utilizing modified silicone rubber tooling

Control of the pressure at the cure temperature of polymer matrix composities is critical to the fabrication of high quality composite structures. Cast silicone rubber has been utilized as a tooling aid to apply pressure to complex composite parts during cure. Due to the high expansion rates of most silicone rubber systems in the 'as received' form it is very difficult to achieve proper pressure application levels at the cure temperature. This study focused on selective addition of silica powder to Aircast 3700 castable silicone rubber. The addition of 5% silica reduced the expansion rate by a factor of 10 compared to 'as received' Aircast 3700. This allows very accurate selected pressure levels to be applied at composite cure temperatures. Governing formulas and experimental test results from silica modified Aircast 3700 castable silicone rubber are presented herein.