German engineers are constructing better containers for refuse vehicles made of light metals and fibre composite plastics.
The new containers will replace the heavy steel superstructures of classic waste trucks and are about a third lighter.
Many municipalities are planning to acquire electric refuse vehicles in order to improve city air quality and protect the environment.
However, these are equipped with heavy batteries or fuel cells and can therefore usually transport less waste than classic waste trucks with combustion engines.
Six German research institutes and companies have therefore joined forces under the 'UTILITAS' project (ultralight structures for commercial vehicles in municipal service operations), which aims to develop containers by joining aluminium frames with fibre glass reinforced thermoplastic panels.
Through the lighter design, electric refuse vehicles would be able to transport as much waste per load as a classic small waste truck.
Heat, press, cool
The researchers are testing various methods to reliably join these materials. One such method involves the use of ‘HeatPressCool-integrative’ (HPCi), a technique developed at Fraunhofer IWS.
A laser is first used to roughen the aluminium components, creating grooves in the metal thinner than a pin and only about 200μm deep. Subsequently, the tool presses the plastic component against the aluminium strut and briefly heats the metal. During this process, the thermoplastic melts onto the aluminium surface, flows into the laser-molded grooves and is anchored there during cooling. After a few seconds, the aluminium and composite plastic are permanently and firmly bonded.
Related article: Laser structuring creates strong metal-polymer bonds
Throught the project the IWS engineers will determine exactly the long-term durability of a HPCi-made lightweight container compared to those made using screw or adhesive solutions. The container will have to withstand high loads in daily use, for example when the vehicle mechanics compress the collected waste.
So far measurements have shown that the HPCi joints can withstand tensile forces equivalent to the pressure of a hydraulic arm of up to 25 megapascals. In addition, previous experiments have shown that the lightweight containers are particularly durable, while also being much easier to repair than glued constructions.
‘This is why the alliance is developing not only the container, but also the related practical production technologies,’ explained Annett Klotzbach, head of the Bonding and Fiber Composite Technology group at Fraunhofer IWS. ‘The important point here is to ensure that the new containers can also be built profitably in small series and be quickly repaired in local workshops.’
The first electric waste trucks with new lightweight containers will soon be seen on the streets, according to Klotzbach: ‘The container prototypes should be ready by the beginning of 2021. We expect the first waste collection vehicles to be on the road within two years.’
The IWS experts are convinced that the new joining process is not only suitable for waste container constructions, but also for lightweight constructions in aircraft, railways, industrial facilities or ships. Industrial customers also intend to use HPCi in the production of dishwashers and other household appliances.
Available for industry
In order to support the broad practical application of their new joining technology, the IWS researchers have developed compact HPCi joining guns that are hardly larger than a standard hand drill. They can be modularly mounted on robots, for example, in order to quickly start a small lightweight production run. The Fraunhofer scientists intend to set up a company soon that will series-produce the new joining guns.
The six partners involved in the UTILITAS project are: Fraunhofer IWS, the Chair for Structural Lightweight Design and Plastics Processing at Chemnitz University of Technology, Marko Pfaff & Co. Spezialfahrzeugbau GmbH, Car systems Scheil GmbH & Co. KG, the PROFIL Verbindungstechnik GmbH & Co. KG and the EBF Dresden GmbH.
