The objective functions are virtually identical, the only difference being the introduction of a vector which expresses the percentage of belonging of a given point to each of the clusters. This vector is submitted to a "stiffness" exponent aimed at giving more importance to the stronger connections (and conversely at minimizing the weight of weaker ones); incidently, when the stiffness factor tends towards infinity the resulting vector becomes a binary matrix, hence making the FCM model identical to that of the K-Means.
I think that except for some possible issue with the clusters which have no points assigned to them, it is possible to emulate the K-Means algorithm with that of the FCM one, by simulating an infinite stiffness factor (= by introducing a function which changes the biggest value in the vector to 1, and zeros out the other values, in lieu of the exponentiation of the vector). This is of course a very inefficient way of running a K-Means, because the algorithm then has to perform as many operations as with a true FCM (if only with 1 and 0 values, which does simplify the arithmetic, but not the complexity)