Geometrical Consideration of Permeation in Elastomers

Elastomer seals for space applications are integral for the success of manned space flight. These seals inhibit the loss of habitable cabin air to the vacuum of Space. The loss of breathable atmosphere due to leaks of a seal must be replaced through the use of a costly make-up air system. A cost-effective sealing solution for long-duration manned space flight is thereby enabled by seal leak mitigation, while maintaining acceptable behavior in other requirements (e.g., closure force, reusability). Thus, there is a need for optimization from a multitude of geometric possibilities. To facilitate the selection of space seals mechanisms, designers and researchers have relied heavily on engineering judgment and intuition in the design phase of equipment. The main geometric hypothesis utilized in past design is that the leak rate depends on two aspects: (1) the permeation path length, and (2) the wetted gas-elastomer contact area. The research detailed herein highlights the necessity for computational prediction methods in the preliminary phase of space seal design. To this end, a series of computational analyses were performed utilizing a compressible permeation approach to elastomeric space seals. Utilizing a simple rectangular domain, the hypotheses were confirmed and are reflected in an analysis of the model equations, however, for one-dimensional flow. Unique to this analysis, additional domains were studied incorporating a periodic perturbation in the sidewalls. The analysis simulated the leak rate of each seal design domain, as manufactured from silicone elastomer S0383-70. Foremost, results highlight the significance of the leak rate prediction methodology, as mere engineering intuition does not always lead to true design optimization. A study in the boundary conditions is also presented, whereas the elastomeric nature of space seal materials can be utilized for a strategic gain in leak rate performance. As an additional benefit, the analysis proved its merit as a cost reduction technique. Whereas by undergoing design iterations in a virtual environment, the cost associated with manufacturing faulty designs are eliminated.