On Thermal Blistering of FRP Chimney Liners

The rate of energy released as delaminations grow in FRP chimney liners subjected to the thermal environments of flue gas is computed by an indirect finite-element approach developed by Rybicki and Kanninen using a single conventional finite element model. The energy release rates are proportional to the work required to close the displacement components of the gap at a double node near the crack tip. The results show that delaminations less than a certain size, depending on the flue gas temperature, are not susceptible to blister formation and unstable growth. Moreover, the growth of delaminations is bounded. The final size of a blister depends upon the flue gas temperature and the level of degradation of the fracture resistahce of the material that occurs over time in a thermal environment. Square shaped delaminations are found to be less susceptible to growth than the rectangular shaped delaminations orientated perpendicular to the angle of wind of the structural laminate. Initial deflection reduces the energy release rate almost proportionally to the ratio of initial deflection to total deflection.