Filament winding process in thermoplastics

Institut ftir Verbundwerkstoffe GmbH, Germany and R. SCHLEDJEWSKI, Montanuniversitaet Leoben,Austria 

Key words in situ consolidation, impregnation, main heater, thermoplastic filament winding. 

Cavity Cylinder with domed ends and pole holes D1 D2 

In Fig. 7.2 a thermoplastic filament winding process consisting of a material rack, a tension controller, a preheating zone, a main heater, a consolidation roller and a mandrel is shown schematically. Beside the material used, the most adjustable process parameters are winding velocity (which is defined by mandrel rotation and crosshead movement), roving tension, temperature, winding angle and mandrel/liner (material and temperature control). 

2 Schematic of filament winding process chain (includes preheating zone and a consolidation roll). 

---

Chapter 7 focuses on the thermoplastic filament winding process for continuous fiber reinforced composites. Thermoset filament winding has been around for over four decades and is routinely used to make axisymmetric structures. In the last couple of decades, researchers have tried to translate... 

Schlottermiiller, M., Lu, H., Roth, Y., HimmeL N., Schledjewski, R. and Mitschang, R, Thermal residual stress simulation in thermoplastic filament winding process . Journal of Thermoplastic Composite Materials, 2003,16(6), 497. 

Other methods such as ultrasonic heating, microwaves, induction heating, or high frequency radiation and furnace heating are of no industrial importance or lead to inferior material properties [28,43-46]. The thermoplastic filament winding process is called in situ consolidation and is schematically shown in Figure 1.11. With such devices, it is possible to process tapes of different widths with winding speeds up to 30 m/min. However, better material properties are derived at speeds of between 6 and 12 m/min [30]. 

There are a number of general references available that contain detailed descriptions of the winding process and equipment itself [5,6], The purpose of this work, however, is to focus on the relationship between processing conditions and final part quality for both thermosetting and thermoplastic matrix filament wound cylinders. In the subsequent sections, an overview of the process will be presented, followed by detailed descriptions of current process modeling techniques and methods for determining cylinder quality. 

Consolidation and development of interlaminar bond strength for thermoplastic matrix composites have been modeled by two mechanisms intimate contact and autohesion. Intimate contact describes the process by which two irregular ply surfaces become smooth (Fig. 13.10). In areas in which the ply surfaces are in contact, autohesion occurs, and the long thermoplastic polymer chains diffuse across the ply boundaries. Filament winding with thermoplastic matrix materials is considered an on-line consolidation process in that local... 

Fiber placement is basically a hybrid of filament winding and tape laying and is a continuous process for fabricating composite shapes, by laying thermoset or thermoplastic preimpregnated tows (in tow or slit tape form) onto a mandrel or tool having concave or convex surfaces. There is no limit to the fiber angle and tows can be added or removed as and when necessary. 

For thermosets, the hollow part processes are filament winding and pultrusion. These processes are limited in shape and structure. There are three hollow part processes for thermoplastics (1) rotational molding, (2) twin sheet thermoforming, and (3) blow molding. 

The impregnated tows can be used for many applications which are generally subdivided into those where the fiber reinforcement is continuous (e.g. filament winding or pultrusion) and those where the tow is cut and the unidirectionally reinforced peUets (discontinuous long fiber reinforced thermoplastics) are then further processed into parts (e.g. in extrusion or injection molding). 

The surface treatment chemistry of glass fiber is normally tailored to match the product function. Reinforcement size chemistries must be compatible with a multitude of processes and with the composite material end-use performance criteria. Processes such as injection molding require chopped fibers with compatibility for thermoplastic compounds. Filament winding and pultrusion require continuous fibers with utihty in thermoset and thermoplastic compovmds. Typically three basic components cue used with glass size chemistries a film former, lubricant, and coupling agent. Readers are directed to the patent literature or [1] and [2] for more specific details. 

---