Lattice defects in two-dimensional hexagonal arrays primarily take the form of dislocations, point defects that lie at the mutual terminus of two incomplete rows of material. The dislocation core is composed of one 5-fold and one 7-fold coordinated domain within the otherwise hexagonally coordinated lattice. Using scanning force microscopy to view the nanodomains of a 2D hexagonal array of vertically oriented poly(cyclohexylethylene)-poly(ethylene)-poly(cyclohexylethylene) (CEC) cylindrical triblock copolymers, we show that the domains which compose dislocation cores adjust their sizes (5-fold coordinated cylinders contract and 7-fold coordinated cylinders expand) in response to the stress field associated with the defect. Similar analysis was performed on a two-dimensional self-consistent mean-field theoretical simulation of a similar triblock copolymer system, yielding good agreement with experimental results.