Stiffness analysis of polymer composites filled with spherical particles

1 Stiffness analysis of polymer composites filled with spherical particles 

While for a hexagonal array the same relationship is expressed as 

It should be noted that the described axisymmetric unit cells do not represent actual repetitive sections of a material but their dimensions are related to the 

In addition to the boundary conditions (5.82a-5.82d), it is required that the displacement components should vanish on the surface of a rigid filler. 

The highly constrained boundary conditions shown in Equations (5.82a) to (5.82d) can be relaxed via replacing conditions (5.82c) and (5.82d) by = 0 on r = ri which is the stress-free condition along BC. Using this set of uncon-straint conditions the outer side waU of the cell does not remain straight and 

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