Thin-walled spherical balloon, inflation

Calculate the pressure required to inflate a thin-walled spherical balloon made from a Hoakian elastic material. 

Hi) Inflation of a Thin-Walled Spherical Balloon In this case, if the balloon radius expands by a factor k, equibiaxial extensions of ratio k will be set up in the balloon, with a shrinkage ratio 1 /k of the wall thickness to maintain the rubber volume constant. The circumferential stresses ti and t2 are equal and given by... 

FIGURE 1.11 Inflation of a thin-walled spherical rubber balloon. Solid curve Eq. (1.26) with Jm = oo (from Gent, 1958). 

The internal pressure P required to inflate a small spherical cavity in the center of a thick block can be obtained by integrating the contributions from concentric shells (thin-walled balloons) given in the preceding section. The result is (Gent... 

---