The Van Wees creels are being used in our UD lines for unrolling the fibers at a constant tension. Van Wees has developed spool holders that are equipped with an adjustable core, making it possible to fit a range of cardboard tubes from 50 millimeter up to 95 mm.
For unwinding technical yarns such as Polyamide, Polyester, Aramids and Ultra High Molecular weight Polyethylene Van Wees has developed and builts Creels with the yarn guiding by round eyelets. At appropriate positions in the creel, the yarns are guided up to the front of the creel.
In case of Carbon fibers, the tows are guided with specially formed eyelets and yarn guidings that keep the tows spread and prevent the tows from twisting as they travel to the downstream machine.
The Glass roving creel is equipped with spool holders that can take the heavy ( up to 25 kilograms) rolls. These, normally from the inside being pulled, tows are unwound tangentially thereby preventing the occurrence of twist in the fiber. The glass rovings are in the same manner guided as the carbon fiber tows. Yarn tension is regulated in the creel, from relatively simple hand adjustment up to automated adjustment for the entire creel or by each row individually.
UD impregnation machines
Van Wees can offer three different machines for the impregnation of fibers and fabrics.
- Dispersion impregnation
- Thermoset impregnation by reverse roller coater
- Thermoplastic resin impregnation with inline extruder
The dispersion impregnation machine is used for the production of UD prepregs for the technical textiles (for example ballistics) industry. The process is very stable and the impregnation level is high due to the easy penetration of the resin in the fibers. The Van Wees unit has a post spreading device making the uniformity even better. The resin content in the UD tape can be adjusted by tuning the solid content of the dispersion. Speed of impregnation is up to 20 meters/minute.
The thermoset prepregs are made as a one step process. The resin is applied on the carrier (silicone coated paper) by the reverse roller coater. The spread fibers are applied on the resin film and by heating the material the impregnation takes place. For further impregnation, calibration and consolidation, one – two or three calendar units can be integrated in the machine. UD tapes as well as fabrics can be impregnated on this machines. Speed of impregnation is in the 3–10 meter/minute range.
For impregnation of thermoplastic resins, Van Wees has developed a process in which the resin film is made by melting the polymer in an extruder and metering the film thickness on the impregnation roller. The spread fibers are impregnated up to a certain level on the impregnation roller and post impregnation takes place before final consolidation and being cooled. Speed of impregnation is in the 3–15 meter/minute range.
The UD tapes or prepreg fabric can be wound on double winders. In that case the impregnation process is not interrupted and the material is stored in a compensator unit during rolls change.
Crossply material is a laminate consisting of minimum 2 layers of unidirectional fiber-layers, laminated together to form a multi directional laminate. Because the fibers in the laminate are positioned in a completely stretched manner, the construction yield of the material is nil. In contrast to woven or knitted fabrics, the forces exerted on the Crossply laminate are absorbed directly by the fibers.
Two different processes are possible with the Crossply machines.
- Single layer process
- Multiple and Multi-axial process for tailored blanks
The single layer process is used in those cases where the second layer is applied in the impregnation machine or in a second pass on this machine. This process is used for the ballistics industry in which case the UD tape is oriented at 90 degree and for the thermoset resin composite industry in which orientations of 90–45 degree are possible.
The multiple layer process is used for inclusion of the second layer on the Crossply machine. The second layer can be oriented in an angle of 90 up to 45 degree. This high speed process is especially interesting for the thermoplastic composites production. The material is spot welded after which it is wound. Multiple rolls can be consolidated in a lamination line. It is also possible to cut the material and do the consolidation in a mold or before molding by infra-red heating.
For making wider Crossply laminates and tailored blanks, it is possible to use multiple UD tapes next to each other as 0 degree layer. The second layer will bridge these wide UD layer and form a stable laminate which is rolled on large diameter drums.
Speed of operation is dependent on the working width up to 10 meters/minute.
Van Wees manufactures laminating lines, used in the Crossply process for consolidation of the materials, by integrating calenders or belt laminators. The Crossply material is laminated by heat and pressure and cooled down between the belts. The laminate can be covered with films, for example as used in the soft ballistics industry. In the case of technical textiles the material is wound on large drums and if needed, ready for inspection.
Crossply laminates or tailored blanks can be made using multiple rolls. In that case the number of unwinding positions is determined by the layer thickness. Dependent on the laminate thickness and stiffness, the material is rolled or cut and stacked.