Turbine engine airfoils are teardrop-shaped structures (in cross-section) with a rounded leading edge and a wedge-shaped trailing edge tapering down to a minimum thickness. From an aerodynamic perspective, tapering down the trailing edge to a zero thickness would be ideal as such an arrangement would potentially eliminate the bluff body close-out shape of the trailing edge and its attendant drag-induced flow separation. However, from a practical standpoint, both manufacturing constraints and stiffness requirements limit how thin a trailing edge can be made. In particular, adequate stiffness of the trailing edge is required to enable the airfoil to resist flutter excitation, early fatigue-induced cracking, and structural failure of the airfoil. Moreover, current lightweight airfoil materials such as aluminum, organic mesomorphous carbon composites, and titanium have low elastic modulus, which necessitates thicker-than-desirable trailing edges.
Clearly, there is a need for airfoil design strategies and manufacturing techniques which allow for thinner trailing edges while improving the stiffness and resistance to fatigue-induced cracking at the trailing edge.