Improved lightweight composite-material structures have been invented to protect persons and equipment during aircraft and ground-vehicle crashes. These structures are designed to hold their initial shapes and sustain rated loads under normal operating conditions and, during crashes, to undergo sustained deformation with high stroke efficiency at tailored crush loads to absorb kinetic energy. The advantages offered by these structures over prior crash-energy-absorbing structures, including composite-material ones, are that these structures can be fabricated by use of relatively simple, cost-effective techniques and the designs of the structures can readily be adapted to a variety of applications.

Foam Blocks Designed To Be Crushable along their vertical axes are wrapped with resin-impregnated fabric, then stacked horizontally. The stack is over-wrapped with another resin-impregnated fabric, and the resins are cured to form a unitary beam.

One example of design and fabrication of a structure of this type is that of a simple rectangular parallelepiped beam comprising a stack of cells (see figure). The cell cores are designed to be crushed along their longest axes. First, the cells are fabricated, starting from block-like cores, which could be hollow and/or made from a closed-cell, low density, rigid polymeric structural foam. Each core is wrapped with a woven fabric or other continuous fiber reinforcement. The wrap is impregnated with a suitable matrix resin by use of any of a number of established techniques.

The cells are stacked in the desired orientation along the intended longitudinal axis of the beam. In a typical application, the beam might be intended to serve as a subfloor structure in an aircraft, where it could protect occupants against excessive vertical crash loads by yielding vertically: in this case, the preferred orientation of the long axis of each cell in the stack is vertical. Skins of resin-impregnated continuous fiber reinforcement, possibly similar to those of the individual cells, are wrapped around the stack, holding the cells together firmly. Then the resins are cured, yielding a unitary, rigid structure, wherein the bonded skins at the interfaces of adjoining cells constitute additional transverse reinforcements. If there is a requirement that the beam retain its post-crash integrity, then the skin should be composed of tough fibers (e.g., an aromatic polyamide or polyethylene fabric).

Structures of this type are not limited to a simple beam design and fabrication sequence like those described above. Structures can have more complex regular or irregular shapes, can be fabricated in different sequences, and can be made from different foams, fibers, and resins. The materials, dimensions, fiber orientations, and other design parameters can be selected to obtain specified direction- dependent crushing characteristics while satisfying shape and load-bearing structural requirements during normal operation.

This work was done by Sotiris Kellas for and Huey Carden of Langley Research Center. For further information, access the Technical Support Package (TSP) free on-line at  under the Materials category.

This invention has been patented by NASA (U.S. Patent No. 5,746,537). Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to

Rheal Turcotte,
Technology Commercialization Program Office,
NASA Langley Research Center
at (757) 864-8881
or e-mail at This email address is being protected from spambots. You need JavaScript enabled to view it..

Refer to LAR-15397.