fabricreinforceddiaphragm.cn Rubber diaphragm|Disciplinary

DIAPHRAGM FORMING OF THERMOPLASTIC COMPOSITES USING SILICONERubber diaphragm
The Disciplinary group for Composite Materials and Structures has a long history of research on thermoforming of thermoplastic composites. One of these thermoforming techniques isRubber diaphragmforming. This paper describes the development of diaphragm forming with siliconeRubber diaphragm. The existing method ofRubber diaphragmforming uses two thermoplastic diaphragms in between which a laminate is placed. For laminates containing engineering thermoplastic matrices, like PEI, PPS and Peek, high processing temperatures of up to 400℃ are required. A suitable diaphragm material is polyimide film. The main drawback, apart from the high costs, is that it remains plastically deformed after one production cycle.
Every single product consumes two polyimide films, making the process rather expensive. The objective of this paper is to present a study on the replacement of polyimide films by reusable silicone diaphragms. Most silicone rubber suppliers produce high temperature grades of silicone that have an outstanding long term heat stability temperature of 250℃. Some claim a maximum temperature of up to 320℃. Above the maximum temperature, short-term exposure is possible, however, the time and number of cycles is not known. A rubber sheet test set-up has been developed to investigate the behaviour of silicone diaphragm forming conditions. A single sheet of silicone rubber is deformed into a hemispherical cavity in a hightemperature environment. Displacement of the silicone rubber and deforming force is monitored. Three types of silicone rubber, certified by manufacturers for temperatures up to 280℃, have been tested in the rubber tester. With increasing temperature their stiffness decreases. At 100℃ and 200℃ these rubbers can be deformed twenty times in a row showing little or no plastic deformation. At 300℃ the number of runs possible decreases considerably to only 7, and permanent deformation of theRubber diaphragms increases considerably.