Thermoforming of reinforced thermoplastic stiffened structure

For thermoforming of continuous fabric reinforced thermoplastics, fabric sh earing is the dominant deformation mode. The maximum shearing angle depends on the textile architecture and it is expressed as a locking angle, i.e., the smallest possible angle between warp and weft yarns. Wrinkling and buck ling occur when the locking angle is exceeded or when too high compression stresses are introduced in the fabric during forming. To avoid these undesi red effects membrane stresses must be introduced into the fabric, e.g., by using blankholders. In the first part of this paper a new pneumatic clampin g device will demonstrate the advantages of easy handling and flexible forc e variation. The second part deals with a technology to form and join conti nuous fiber reinforced fabrics in one step: Tailored Blank Technology. This method reduces the manufacturing steps and offers the advantage to produce parts with different thicknesses or to add profiles and inserts to the mai n sheet. First results about the temperature windows will be discussed for glass fiber reinforced polypropylene.