Structural Integrity of Flat Silicon Panels for Nanosatellites – Modeling and Testing

To utilize the high mass fraction of silicon material in a nanosatellite based on microelectro-mechanical systems, part of the structural function has been assigned to the flat silicon stacks embracing these systems. Three modules for destructive testing in bending, warping and shearing cases were built with 68x68x1 mm silicon stacks bonded in aluminium frames by in-situ casting of silicone rubber. The rubber served as the deformation zone between the stiff and brittle silicon stacks and their weaker and ductile aluminium frames. A special test module of the same size was built with strain gauges of Nichrome (thin film deposited directly on the surface of the silicon stack). Elastic deformation tests on this as well as simulations using finite element analysis were performed for bending, warping and shearing loads of up to 80, 40 and 99 N, respectively. The test module was disassembled after the test series and examined. The actual thickness of the rubber was measured and entered into the model for simulation. The correlation between simulations and experimental measurements was good with deviation of about 30%. The results show that the rubber works well as a mechanical interface. Its thickness influences the stress in the silicon stack significantly. The silicon stack stiffens the module by a factor of 46 and lowers the stress in its frame 24 times in shearing mode, which is the most relevant loading case for the satellite framework. Thus, the concept of using flat silicon panels as structural elements is fully feasible.