NIAR and KraussMaffei jointly develop lightweight window plugs for cargo aircraft conversion

The National Institute for Aviation Research (NIAR) at Wichita State University in the US and KraussMaffei combine their expertise to develop lightweight solution for window plugs for passenger to cargo aircraft conversions.

NIAR and KraussMaffei collaborated to develop lightweight solution for aircraft window plugs.

Passenger to cargo conversions are common as aged aircrafts no longer offer comfort but still works as cargo aircrafts. The conversion requires replacing acrylic window plugs with metallic alternatives for ease of maintenance.

Fiber-reinforced thermoplastic solution for window plugs

NIAR and KraussMaffei jointly develop an optimized, lightweight solution using FiberForm technology, a modern fiber-reinforced thermoplastic composites that offer the same stability at lower costs, less weight, and less processing time.

With FiberForm, a fully consolidated fiber-reinforced thermoplastic sheet known as organosheet is inserted into the tool, formed and overmolded with a thermoplastic polymer.

The window plugs are produced on a GXW 450-2000/1400 with a swivel platen. They are designed with the oval-shaped geometry of the original with appropriate design modification, including adding ribs to stiffen in order to withstand pressure loads.

GXW 450-2000/1400 with swivel platen unit from KraussMaffei.

In order to achieve the desired mechanical properties, the team of Dr Waruna Seneviratne from NIAR and Eugen Schubert from KraussMaffei use high-performance plastics LM-PAEK reinforced with AS4 carbon fibers for the 16-ply organosheet and 30% chopped-fiber-filled PEEK for overmolding the ribs.

Shorter cycle time and lighter weight

FiberForm technology allows fast injection molding, which results in short cycle time, compared to metal machining. 40 window closures can be produced within an hour.

In addition, the thermoplastics used for FiberForm offer the possibility of welding components, have a high impact strength, are resistant to high temperature, chemical and environmental influences, and are also flame retardant.

Nevertheless, the composite overmolded version of window plug weights 20% less compared to its 590-gram metal counterpart. The team is already working on further optimizing the structure to make it about 40% lighter than the metallic counterpart.

With two years of partnership, NIAR and KraussMaffei jointly work from supply chain, machine set up, to on-site with process development.

Dr. Waruna Seneviratne and Eugen Schubert have also recently published a technical paper about this project. The paper with the title “Ultra-High-Rate Manufacturing of Thermoplastic Window Plug Using Hybrid Overmolding” has achieved 1st Place in the outstanding technical paper awards for SAMPE 2024.