Metal Inserting for Brittle Materials 

The challenge of direct attachment to brittle materials has been solved with the use of bonded threaded inserts of low expansion metal.  Due to the brittle nature of SCSi, it cannot be threaded without considerable risk of residual damage in the threads, thus reducing the strength of the intended connection.  Therefore, threaded inserts must be used with smooth mating surfaces and a bonding agent. 

McCarter has studied several bonding agents for SCSi, specifically #2216 epoxy, 80Au/20Sn solder, and GK frit, and has found that the method developed here at McCarter under the direction of Frank Anthony is the most predictable, stable, and reliable.  We use this method to fabricate complex components from an assembly of simpler parts.

We tested the strength of our inserting process by conducting a videotaped fatigue test on six different frit-bonded samples.  The failure point ranged from a low of 281 lbs for a SCSi sample to a high of 1239 lbs for a SiC sample. The silicon tended to fail before the frit-bonded joint meaning that the initial quality control in selecting Zero-D material is critical. 

In addition, our frit bonding process has demonstrated cryostability and nuclear stability in independently conducted tests.  The frit-bonded metal inserts allow for direct attachment thereby eliminating mounting cans, fixtures, and other hardware along with the cost, weight, and mass attributed to them. 

The inserts create a modular concept for production and auto-alignment functions, which together, reduce the cost and time for assembly.  We use 39NiFe, created by Carpenter Alloys, a cryostable material for space applications, to manufacture inserts.