Due to the high material costs, process automation in composites manufacturing is one of the central themes of the fourth industrial revolution.
Existing curing processes in composite production are programed to predefined cycle times and cannot be modified without extensive effort. Material, humidity, and temperature fluctuations cannot be compensated and there is a possibility of waste production.
However, if the processing time is actually longer than it needs to be in order to permit for an indefinite duration of curing, the process becomes unprofitable because of the resulting increase in unit costs. Thus, the goal is to arrange intelligent production systems that enable strong and dynamic production based on the material behavior.
Which Data is Necessary to Ensure the Desired Component Quality with Regard to Mechanical Performance?
The restriction for a good component is provided after the component design and the layout by the manufacturing process: the resins must totally fill a cavity with or without semi-finished fiber products and the tool may only be opened again after adequate cross-linking. Temperature and pressure sensors have been used for over 15 years and their data is used to help regulate the process and outline quality criteria.
Pressure sensors offer information about the filling of a cavity via the cavity pressure. Temperature sensors track the mold temperature to process the resins in the right process window. However, sensor technology, which describes the actually critical material behavior, specifically the cross-linking reaction, has only been used inadequately thus far. So, a few components from the automotive industry, which have not found the middle ground between the required cost reduction and high component quality, have been in the prototype phase for a number of years.
So as to solve the complications, a combination of sensors is needed that allows an understanding of all areas of a process. In the author’s view, three types of sensors are present to enlighten the invisible in-mold processing and to allow process automation in composite manufacturing:
- temperature sensors
- pressure sensors
- dielectric sensors
Dielectric Sensors — a Game Changer for Composite Process Automation
Dielectric sensors have an advanced sensor technology and a high sensitivity. They match the industrial necessities in a wide temperature and pressure range and clearly surpass the possibilities of certain alternative approaches. In the past, however, the dielectric method was struggling with electrically conductive fillers.
A recently developed sensor by NETZSCH Analyzing & Testing provides the option to describe the material behavior of polymers and carbon composites with other electrically conductive fillers in the invisible and crucial curing process in the tool. This provides robust processes, higher productivity and cost savings.
Tool-Mountable Coated Comb Electrode (TMC 18c)
This novel sensor, relevant in challenging process conditions, is unique in the world and exceeds state-of-the-art. The new sensors accomplish unmatched performance in dielectric measurement, and their application range has also been considerably expanded:
- continuous operating temperature of 300 °C
- extremely scratch resistant owing to the ceramic-based material
- pressure resistance 300 bar
- resistance to solvents
With this latest sensor, NETZSCH Analyzing & Testing has paved the way for shifting its knowledge in material characterization and kinetic modeling to manufacturing for process automation.
Based on the recently created sensor technology and the demands of research institutes and industrial companies globally, the Process Analytics business field is designing the process package of the future. The task is to curtail waste through dynamic process control, adjust the cycle time to the material response, and create composites in a sustainably competitive manner.
The following illustration signifies the cure behavior and the development of the conversion during the manufacturing of an automotive component using the SGL Carbon SE E420 carbon fiber prepreg.
Cure behavior of the SGL E420 carbon fiber prepreg during the manufacturing of an automotive component.
This information has been sourced, reviewed and adapted from materials provided by NETZSCH-Gerätebau GmbH.
For more information on this source, please visit NETZSCH-Gerätebau GmbH.