Microelectromechanical systems (MEMS) structures are typically fabricated from brittle silicon based materials. When tested to fracture they show wide part-to-part scatter in strength. Demonstrated is a methodology with which the probabilistic strength of complex shaped parts with intrinsic dimensional uncertainty can be predicted from simple test specimens. To simulate the simultaneous effects of stochastic material strength, complex stress states, and that of the dimensional variability on the probabilistic strength response of the specimens the NASA developed CARES/Life code was used in conjunction with the ANSYS Probabilistic Design System (PDS). The CARES/Life code modeled stochastic material strength and the effect of complex stress states while ANSYS PDS was used to simulate specimen-to-specimen dimensional variation. This technology was tested by predicting the strength response of micro sized (in this case sub-millimeter sized) tensile specimens with fabricated through thickness holes (hence concentrating stress) from specimens without holes. Single crystal silicon carbide tensile specimens were fabricated with deep reactive ion etching (DRIE). The etching process resulted in high-aspect-ratio (large out-of-plane dimensions relative to in-plane dimemsions) specimens with nearly vertical sidewalls but with a sidewall roughness greater than top and bottom surfaces. Specimens with an elliptical hole, a circular hole, and without a hole (and hence with no stress concentration) were made. There was a large amount of scatter in the measured fracture strengths (typical for ceramics) but the average fracture strength was observed to increase with higher stress concentration (from circular hole to elliptical hole). Also measured was the specimen-to-specimen dimensional variation. An ANSYS macro code was developed such that simulated fracture strengths could be generated for the specimens with stress concentration and dimensional variation using CARES/Life and ANSYS PDS. The analytical predictions correllated well with the specimens with the circular hole but not quite as well to the specimens with the elliptical hole feature. This work demonstrated that the Weibull distribution as used in CARES/Life describes MEMS strength, that the surface area of the (relatively) rough etched sidewalls likely controled the failure response, that part-to-part variations in properties such as dimension can be accounted for in the reliability/design analysis, and that, at least in cases of moderate levels of stress concentration, parts can be sucessfully designed from simple test specimens data strengths could be generated for the specimens with stress concentration and dimensional variation using CARES/Life and ANSYS PDS. The analytical predictions correllated well with the specimens with the circular hole but not quite as well to the specimens with the elliptical hole feature. This work demonstrated that the Weibull distribution as used in CARES/Life describes MEMS strength, that the surface area of the (relatively) rough etched sidewalls likely controled the failure response, that part-to- part variations in properties such as dimension can be accounted for in the reliability/design analysis, and that, at least in cases of moderate levels of stress concentration, parts can be sucessfully designed from simple test specimens data.

Spray CVD has become an advancing technique where a room-temperature precursor solution is ultrasonically nebulized, and is swept into a two-zone, hot-wall reactor

The invention disclosed herein includes a technique for sequestering single walled carbon nanotubes (SWCN) by a polymer. The resulting composite can be dissolved into epoxy resins and hardeners for curing into thermoset plastics. Its incorporation into thermosets is for the purpose of acting as reinforcement.