MRO-friendly PMI foam core

Evonik Industries AG took the unusual step of developing a new polymethacrylimide (PMI) foam product that can mimic honeycomb core’s tendency to permit visible laminate damage.

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Evonik Industries AG (Essen, Germany) took the unusual step of developing a new polymethacrylimide (PMI) foam product that can mimic honeycomb core’s tendency to permit visible laminate damage. Evonik’s spokesperson Mary Erwin explained that during mandatory aircraft inspections, it is the damage that does not show on aircraft surfaces that most concerns maintenance and repair organization (MRO) personnel. Historically (not to mention ironically), Evonik’s ROHACELL foam products support the faceskins of aircraft structures so well that minor laminate damage may not be in evidence on the visible exterior surface. Aerospace fabricators report that the free-space between honeycomb walls more easily permits laminate indentation or perforation. For that reason, Evonik developed new ROHACELL HERO PMI foam core. As the photos show, the new PMI foam (left) responds like honeycomb (right), yet still prevents the incursion of moisture that occurs with damaged honeycomb, which — in the temperature extremes endured by aircraft — can freeze and thaw, causing faceskin/core delamination.