By reason of the high material costs, process automation in composites manufacturing is one of the core themes of the fourth industrial revolution.
Current curing processes in composite production are set to predefined cycle times and cannot be adapted without considerable effort. Material, temperature and humidity fluctuations cannot be compensated and there is a risk of waste production.
However, if the processing time is actually longer than it needs to be in order to allow for an unknown duration of curing, the process becomes unprofitable due to the resulting increase in unit costs. Therefore, the goal is to set up intelligent production systems that enable robust and dynamic production according to the material behavior.
Which data is necessary to ensure the desired component quality with regard to mechanical performance?
The limitation for a good component is given after the component design and the layout by the manufacturing process: the resins must completely fill a cavity with or without semi-finished fiber products and the tool may only be opened again after sufficient cross-linking. Pressure and temperature sensors have been used for more than 15 years and their data are used to attempt to control the process and define quality criteria.
Pressure sensors provide information about the filling of a cavity via the cavity pressure. Temperature sensors monitor the mold temperature to process the resins in the correct process window. However, sensor technology, which characterizes the actually critical material behavior, namely the cross-linking reaction, has only been used insufficiently so far. Therefore, some components from the automotive sector, which have not found the compromise between the required cost reduction and high component quality, have been in the prototype stage for many years.
In order to solve the difficulties, a combination of sensors is required that allow an insight into all areas of a process. In my opinion there are three types of sensors inevitable to enlighten the invisible in-mold processing and to enable process automation in composite manufacturing:
- pressure sensors
- temperature sensors
- dielectric sensors
Dielectric sensors – a game changer for composite process automation
Dielectric sensors have a high sensitivity and an advanced sensor technology. They meet the industrial requirements in a wide pressure and temperature range and clearly exceed the possibilities of some alternative methods. But the dielectric technique was struggling with electrically conductive fillers in the past.
A newly developed sensor by NETZSCH Analyzing & Testing provides the possibility to characterize the material behavior of carbon composites and polymers with other electrically conductive fillers in the invisible and critical curing process in the tool. This brings robust processes, cost savings and higher productivity.
This new sensor, applicable in harsh process conditions, is unique in the world and exceeds state-of-the-art. Not only do the new sensors achieve unparalleled performance in dielectric measurement, but their application range has also been significantly expanded:
- continuous operating temperature of 300°C
- pressure resistance 300 bar
- extremely scratch resistant due to the ceramic based material
- resistance to solvents
With this new sensor, NETZSCH Analyzing & Testing has laid the foundations for transferring its knowledge in material characterization and kinetic modeling to manufacturing for process automation.
Based on the newly developed sensor technology and the requirements of research institutes and industrial companies worldwide, the Process Analytics business field is developing the process package of the future. The mission is to minimize waste through dynamic process control, adapt the cycle time to the material response and make composites sustainably competitive.
The following picture represents the cure behavior and the evolution of the conversion during the manufacturing of an automotive component using the SGL Carbon SE E420 carbon fiber prepreg.
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Alexander Chaloupka studied physics at the University of Augsburg and was, as a student, working at the Application Center for Material and Environmental research (AMU). In 2013 he joined the branch Functional Lightweight Design of the Fraunhofer Institute of Chemical Technology ICT (now Fraunhofer IGCV) where he was responsible for thermophysical and chemical analysis and rheology. In 2016 he got contracted by NETZSCH Analyzing&Testing as a R&D project engineer to push the application of material characterization during manufacturing for process control. In 2018, after developing a worldwide unique dielectric sensor concept with the team at NETZSCH Analyzing&Testing, Alexander Chaloupka became the Manager of the Business Field ‘Process Analytics‘. Process Analytics is NETZSCH‘s contribution to an intelligent and dynamic sensor based production of the future.
Alexander has more than 6 years of experience in various production processes of polymer materials and polymer-based composites. He is a specialist in characterization and kinetic modeling. With the Process Analytics business field, he has focused on real-time sensor technology and model-based algorithms for intelligent, automated and robust production to create – together with his team – solutions of tomorrow.