Aircraft manufacturing requires the most efficient design at the lowest cost. To meet aircraft manufacturers’ stringent requirements on damage tolerance and damage visibility after impact events such as bird strikes or hail, Evonik Industries has introduced a structural foam core for sandwich components called Rohacell Hero.
Impact tests have confirmed the required damage visibility for hailstones, runway debris or tool drops with impact energies of up to 35 Joule. The Rohacell Hero’s closed-cell r foam leaves the damaged area impermeable because it spreads the damage.
High-rigidity components commonly use honeycombs as core material. However, fabrication is complex and expensive due to the open hexagonal cells and low inherent rigidity, according to Evonik. On the other hand, foam cores require only a simple one-shot manufacturing process and save on core filler or adhesive film, which reduces processing time, costs and weight.
A direct weight and cost comparison between a honeycomb design and a Rohacell Hero on a nose gear door reduced the vehicle’s weight by 19 percent, and the cost of the CFRP component was 25 percent less. Honeycomb structures may also accumulate water in their cells during flight, resulting in greater weight and a possible secondary effect: debonding of the covering layers. The foam design solves these problems, reducing an airlines’ operating costs.