Processing of continuous fiber-reinforced plastics with 425°C heating table

  • Processing temperatures of up to 425°C
  • Manufacturing of laminates based on thermoplastics such as PPS, PEI or PEEK
  • Entire process chain under one roof

Continuous fiber-reinforced plastics, based on thermoplastics, are growing in popularity. High processing temperatures are a crucial regulating factor for reliable processing of these materials. The heating of reinforcing structures, such as fabrics made from thermoplastic pre-impregnated uni-directional fiber-reinforced UD tape, also requires a high level of process control and reproducibility. Based on a process developed by the Fraunhofer Institute For Chemical Technology (ICT) to consolidate UD tape supports, the press manufacturing company Wickert addresses these requirements with a flexible complete system.

Market requires increasingly high-performance matrices

At the end of 2014, the press manufacturer delivered a high-temperature contact heating table that allows processing temperatures of up to 425°C. This is being used by Fraunhofer ICT in the thermoplastics processing (TP) working group in the Polymer Engineering Department. One of the research focuses of the TP working group is local continuous fiber reinforcement, which also covers the processing of continuous fiber-reinforced semi-finished products such as UD tapes.

“In the past, the most you could process was fabrics made from technical thermoplastics such as PA6 or PA66, but the market now requires increasingly high-performance matrices” says Raphael Jauch, project manager at Fraunhofer ICT. His aim is to be able to process tape materials with matrices from high-performance thermoplastics such as PPS or PEEK, thereby entering a new dimension in applications.

The heating table in use at Fraunhofer Institute for Chemical Technology (ICT)

The heating table in use at Fraunhofer Institute for Chemical Technology (ICT)

Entire process chain under one roof

Fraunhofer ICT houses the entire process chain under one roof. The fabrics are manufactured at the Augsburg site by the Functional Lightweight Design project group (FIL). Here, the UD tapes are processed into the desired reinforcement structures in the so-called RELAY process (Rapid Efficient Layup) with any given layer set-up. The UD tapes are placed precisely on a moving table in layers and “spot-welded” using ultrasound. The orientation of the tape, and therefore the fibers, can be set in an infinitely variable way by rotating the table and can therefore be adjusted optimally to any load. These fabrics are then processed further and consolidated in a two-step HTP process (heat/transfer/press). It is here that the newly developed high-temperature contact heating table from Wickert comes into play, heating up the fabrics before they are pressed.

In order to manufacture laminates with the best possible quality and reproducible properties, the individual layers must be bonded together in this process step without any air pockets. The decisive factors when it comes to heating the fabrics include homogeneous temperature distribution and high plane parallelism for the heating plates.

Laminates based on thermoplastics such as PPS, PEI or PEEK

This new systems engineering now allows to manufacture laminates based on high-performance thermoplastics (such as PPS, PEI or PEEK) that are of great interest to users in the automotive and aerospace industries, both in terms of material characterization and further processing into complex high-temperature components.

Processing temperatures of up to 425°C

The maximum product dimensions that can be processed are approx. 1,100 mm x 1,100 mm. With a heat output of 2 x 50 kW, the maximum temperature of 425°C can be reached very quickly from room temperature. Both heating plates are equipped with 6-zone temperature control designed specifically for this purpose, making it quick and easy to make material-specific adjustments. The control accuracy of the heating element zone monitoring system is +1.0°C.

The press features a wide variety of operating modes: the contact heating table can be time- or temperature-controlled, which results in high product reproducibility. All process-related data, such as the target/actual temperatures of the heating plates, product temperatures, heating and stop times and the entire cycle time, are recorded, monitored and displayed.

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