The invention relates to a motor vehicle beam shell designed to be placed behind a bumper skin, said shell being provided with a recess for receiving a strength member inside it, the strength member being, for example, a strength member made of metal, in particular of aluminum, or a strength member made of a composite material incorporating a metal. The beam is provided with shell cladding which interfits with the shell, thereby forming a hollow body defining a recess for receiving the strength member.