An annularly shaped modular debris barrier can be mounted to an internal or an external member that are spaced apart to define an annular gap that could collect debris. The modules rotationally lock. Modules have circumferential segments that can be initially spaced apart to promote flexing that can occur when there is relative axial movement between the structures that define the annular gap. The gaps between segments are circumferentially offset as between adjacent segments to create a labyrinth through which the fluid can move in opposed direction while at the same time causing the debris to be retained. The segments stay in a flexed condition to exert a contract stress on the free ends thereof that touch the adjacent structure.