The present teachings provide a reinforcement for a cavity. The reinforcement may include a carrier having a length extending along an axis between a first end and a second end. The carrier may include one or more longitudinal structures and one or more transverse structures. The carrier may also include one or more walls joined together to form one or more cavities extending along the axis. The carrier may have a cross-sectional shape roughly corresponding to the cross-sectional shape of interior of a hollow structural member. The device may also include a secondary material placed over the carrier. The secondary material is configured to expand, seal, reinforce, or a combination thereof upon application of a selectable stimuli and adhere to the interior of the cavity to provide reinforcement of the same.