Thermoplastic Honeycomb Sandwich for Overmolding Into Thinner Lightweight Composites

Injection overmolding of continuous-fiber/thermoplastic prepregs, or “organosheets,” is gaining traction in lightweight structural composites for automotive, electronic and other applications. At last fall’s K 2019 show in Germany, Econcore of Belgium exhibited a new range of overmolding materials that offer potential for faster molding cycles and other benefits. ThermHex organosandwich materials, produced by Econcore’s ThermHex Waben GmbH subsidiary in Germany, are made from extruded PP film, which is folded into a continuous honeycomb and then covered on both sides with a skin of unidirectional, crossply glassfiber impregnated with PP. The PP organosandwich can be preheated, preformed (including local compression to different thicknesses), and then overmolded with PP in an injection press. Honeycombs are now also being made of recycled PET. The company sees PET-based organosandwiches as suited to electrical enclosures, furniture, pallets, and large logistics boxes and trays. Special versions of this product have been made with nylon 6 for high-heat automotive applications and with polyetherimide (PEI) for aerospace parts.

 

 

Econcore says the organosandwich approach allows for production of thinner overall part profiles, because ribs are no longer needed for stiffness. Though the overall sandwich thickness is 6 to 12 mm, the PP/glass prepreg skin on the honeycomb is only 0.5 mm, vs. 1.0 to 2.5 mm for typical organosheets used for overmolding, allowing for faster preheating and cooling. Less material is needed for overmolding, as well, allowing for faster cycles and reduced material consumption.