Expanded, toughened structural adhesives form stiffening materials for vehicular panels and bodyshell structures. The toughened structural adhesive contains an epoxy resin, a rubber, an elastomeric toughener, a curing agent, and an expanding agent. The expanded structural adhesive greatly increases the amount of energy absorbed by the panel or bodyshell structure during an impact. A blowing agent combination of a chemical blowing agent with expandable microballoons provides for especially good energy absorption.