Continuous Profiles with Oriented Reinforcement
A new manufacturing process permits continuous production of fiber-reinforced pipe and profile with a thermoplastic matrix. The process does not start with semi-finished goods and can be economically incorporated into existing machinery.
Until now, there has been no manufacturing method for high-volume production of fiber-reinforced thermoplastic profiles in which the fiber orientation could be optimally matched to the direction of loading. With this in mind, a process for continuously producing closed profiles with a circular cross-section and based on a thermoplastic matrix was developed in the course of a research project at the Technical University of Darmstadt (Technischen Universität Darmstadt).
The so-called PAZ process is a combination of pultrusion and filament winding. In the first step, a thermoplastic pipe is extruded. This pipe is already reinforced unidirectionally by incorporating rovings in the lengthwise direction as it exits the extrusion die. In this way, the take-away forces can be introduced in a controlled manner. In a second step, the extruded pipe serves as the core for filament winding. Next, layers of fiber with a specific orientation are laid down dry on the pipe in a winding station. Any desired fiber orientation is possible, because all orientations can be defined in a geodetically exact way on the basis of the circular cross-section. This makes it possible to match the angle of fiber orientation and layer thickness specifically to operating conditions.
In a subsequent step of the manufacturing process, the pipe passes through a heating zone, where it is pulled over an expanding mandrel and increases in size radially. The actual impregnation and consolidation of the layers take place here. In contrast to existing thermoplastic winding techniques, the reinforcing fibers are impregnated directly during pipe extrusion in the PAZ process and consolidated over the entire circumference by the conical expanding mandrel.
The PAZ process lays the cornerstone for a new, economical manufacturing method for continuous production of fiber-reinforced pipe and profile with a thermoplastic matrix. Decoupling of the winding and consolidation steps is a particular benefit of the process. Thanks to the simple arrangement of the equipment, the process can be incorporated into existing machinery cost-effectively. Since the process does not start with costly semi-finished goods, production is economical.