Continuous Fibre reinforced Thermploastic Material as an Alternative in High Performance Lightweight Structures

Abstract

The focus on process improvements in high performance lightweight structures is mainly located on thermoset material. Resin transfer moulding processes have been developed to decrease cost for high performance structures in competition to prepreg material. However, thermoplastic materials, such as CF/PEEK, CF/PEKK or CF/PPS, offer interesting opportunities despite the higher material cost compared to thermosets. This paper shows two examples using continuous fibre reinforced thermoplastic material and the joining processes among themselves as well as to titanium in a hybrid structure design. Cost reduction is demonstrated using vacuum consolidation, special moulds and several welding techniques. The first example is a rudder from the vertical tail plane of a military aircraft. Several manufacturing steps including forming or shaping with flat plates, positioning stringers during vacuum consolidation, welding of ribs and welding of the central spar are shown. A cost statement is given analysing the overall manufacturing process. The second example shows the design study of a hybrid fan blade of an aero engine, made from titanium and CFRP part joined along an extended surface. The fan blade is a newly developed high performance blade to save weight and to increase the pressure ratio per compressor stage, so that one complete compressor stage is obsolete. A newly developed finite element model for combining titanium and CFRP is introduced and the special aspects of draping and consolidation in low cost moulds are shown. Future prospects are the integration of additional functions into the structure like lightning protection, bird impact improvement and combination of short fibre and continuous fibre material. Heated press processes during consolidating or welding are reducing cycle times. Some examples such as the man hole access cover, door frame or suspension arm in automotive application are shown with feasible process cycles.