Overall Bending Stiffness of a Tube Rod Assembly
Overall Bending Stiffness of a Tube Rod Assembly
(OP)
A polymer tube 2.5mm diameter with a Youngs Modulus = 2 GPa that contains a metal rod diameter 0.75mm with a Young's modulus of 107 GPa. I need to know the overall bending stiffness of the assembly.
If both materials were touching it would be simple i.e.
k = EI , where I = 2nd moment of area. and just add the two stifness values.
However, i need to know how to calculate the stiffness for the above conditions i.e. material not touching.
If both materials were touching it would be simple i.e.
k = EI , where I = 2nd moment of area. and just add the two stifness values.
However, i need to know how to calculate the stiffness for the above conditions i.e. material not touching.





RE: Overall Bending Stiffness of a Tube Rod Assembly
condition similar to springs in parallel, eg. two extension springs side by side bearing a single
load. In this condition the k values are additive, k total = k1 + k2 + k3... If the rods were
stacked end to end you would have springs in series 1/k total = 1/k1 + 1/k2... (the inverse of
electrical resistors) Hope this helps.