ADHESIVE BONDING OF COMPOSITE RIBBON DURING AUTOMATED TOW PLACEMENT

Manufacture of thermoplastic composites by automated tow placement (AT P) currently relies on hearing composite ribbons well above the soften ing temperature of the matrix resin. High temperature causes the ribbo n to deform and deconsolidate, which then requires the application of high pressure to re-consolidate and bond the ribbon to the composite s ubstrate. A significant degree of fiber waviness in the composite comp onents results from ribbon distortion. High placement temperatures and pressures require heavy, expensive tooling and slow placement speeds. To lower required placement temperatures, the addition of a thin adhe sive layer to the ribbon prior to placement was evaluated. Adhesive co ated thermoplastic ribbons were tow placed using gas torch temperature s 400 degrees C below typical settings. Interfacial bond strength of t wo ply composite laminates made from these ribbons was measured. it wa s found that current ribbon dimensional variations and placement accur acy limitations require that the matrix resin be softened to permit es tablishment of full interfacial contact. However, the presence of the adhesive layer was shown to increase interlaminar bond strength at low placement temperatures. With reductions in ribbon dimensional variabi lity, surface roughness, and void and volatile content low temperature placement may become possible.