Abstract: A technique is provided for removing foam mandrel material from a stiffener section of a composite structural member as is employed in lightweight aircraft skin structures. The technique involves the direct pressure glass bead blasting of the mandrel material. By mounting a blasting nozzle within a rubber hose of larger diameter, an airstream containing glass beads may be directed outwardly through the nozzle while evacuating pressure is created in an annular passageway between the hose and the nozzle to evacuate mandrel foam particles as well as spent glass beads. The result is a clean channel within the stiffener section.

Abstract: A lightweight energy-absorbing structure is comprised of a laminate including a plurality of fabrics, pre-impregnated with a thermosetting resin, abutting against a core of cellular foam treated with a charge of filled bonding material. The resulting mixed materials are compressed between two die members while heat is applied to the dies thereby single curing the thermosetting resin and bonding material. Individual sheets of fabric may have a predetermined orientation to increase impact resistance. In a preferred embodiment polyimide open-cell foam may be employed.