Fiber structure woven as a single piece by 3d weaving, and an application thereof to fabricating a composite material part

A fiber structure woven as a single piece by three-dimensional weaving, the fiber structure having first and second opposite surfaces and comprising:

• a first portion having a plurality of layers of weft yarns and forming a first portion of a thickness of the fiber structure between the first and second opposite surfaces;
• a second portion including a plurality of layers of weft yarns and forming a second portion of the thickness of the fiber structure, the weft yarns being arranged in columns each of which includes weft yarns of the first portion and of the second portion;
• and
• in each plane of the fiber structure, a set of warp yarns interlinking the layers of weft yarns of the first portion and the layers of weft yarns of the second portion while leaving at least one non-interlinked zone separating the first and second portions over a portion of the dimension of the fiber structure in the warp direction from an edge of the fiber structure to an end of non-interlinked zone, wherein:
• one or more same first warp yarns interlink layers of weft yarns of the first portion of the fiber structure adjacent to the non-interlinked zone and layers of weft yarns of the second portion of the fiber structure beyond the non-interlinked zone;
• one or more same second warp yarns interlink layers of weft yarns of the second portion of the fiber structure adjacent to the non-interlinked zone and layers of weft yarns of the first portion of the fiber structure beyond the non-interlinked zone;
• paths of the first warp yarns and paths of the second warp yarns cross over in a transition zone extending in the fiber structure in the warp direction from the end of the non-interlinked zone;
• the transition zone extends in the warp direction over a distance that is greater than a pitch between adjacent weft columns;
• and
• the first warp yarns interlink the layers of weft yarns of the second portion immediately after crossing through the transition zone in the warp direction, and the second warp yarns interlink the layers of weft yarns of the first portion immediately after crossing through the transition zone in the warp direction.