Novel "composite" materials using porous sintered stainless steel adherends mechanically "bonded" with synthetic elastomers

Artificial hip joints currently have a life span of 10-15 years because wear of the polymeric acetabular cup causes loosening of the femoral stem. Recent research has shown that compliant layers can extend the life of the joint to possibly 25 years or more by helping to maintain fluid film lubrication. The problem of "bonding" the compliant layer to a metallic cup was approached by manufacturing porous sintered stainless steel substrates with (1) a range of total porosity from 10 to 35%, and (2) graded structures, using a combination of different powder particle sizes and compaction pressures. An elastomeric polymer was "bonded" onto porous metal substrates to create cylindrical test pieces which were subjected to torsional loading. Substantial mechanical interlocking of the polymer in the interstices of the metallic substrates created a "composite" structure, preventing catastrophic polymeric fracture after interfacial failure. Thus the strain, load at failure and apparent energy of adhesion were considerably higher for porous substrates than for dense materials.