A turbofan engine comprising an annular inner wall surrounding tips of the fan blades, a layer of insulating material surrounding the inner wall, and an outer casing including an annular outer wall surrounding the insulating material and concentric to the inner wall and at least two annular rub elements extending radially inwardly from the outer wall through only part of a radial thickness of the layer of insulating material, at least two of the rub elements being in axial alignment with the blade tips at every point around a circumference of the fan, each rub element having a radially inner end spaced apart from the inner wall and made of a material harder than that of the blades, and a containment fabric layer wrapped around a support structure of the outer wall.