Estampage de composites thermoplastiques hautes performances à base de carbone/PPS pour des applications aéronautiques

Abstract

This experimental study is part of the CRIAQ COMP-512 /GARDN BA5 project which aims at manufacturing a structural airplane passenger door corner made of high performance thermoplastic composites. The stamp forming process is used to shape laminates made of carbon fibres reinforced PolyPhenylene Sulphide (CF/PPS). The process consists in heating a pre-consolidated blank, made of pre-impregnated 5 harness satin weave fabric, above its melting temperature. The blank is then quickly transferred to a press in which a tool forms it to a desired geometry. The blank finally cools down in the press Under the application of pressure resulting in a formed part. The target geometry in this study is an S-shape corresponding to the cross section of the door corner. The effects of various blank and tool parameters, e.g., blank stacking sequence, blank thickness and tool radius, on part quality are investigated. In addition, effects of processing parameters such as consolidating pressure, holding time and tool temperature on part quality are also investigated. Part quality is evaluated through thickness variation measurements throughout a part, final angle measurements (spring back effect), crystallinity degree and void content. The mechanical performance of the specimens is evaluated under four-point bending testing. Recommendations are made in order to achieve good part quality and limits of the process in terms of minimum radius of curvature or maximum blank thickness are discussed. Optimum stamping parameters are then used to mould the first double curvature door corners. Four-layer (thin) and ten-layer (thick) laminates were moulded. It is found that a minimum radius of three times the laminate thickness should be used with the thin laminâtes to get the maximum bending moment. In addition, increasing the radius decreases the stiffness of the part. Nevertheless, the thin laminates are more sensitive to changes in the radius of curvature than the thick laminates for the same tool ratio, i.e. the ratio between the inner tool radius and the blank thickness. A minimum stamping pressure of 3.3 MPa was identified to get the good material consolidation and mechanical performance. However, no effect of the pressure was observed on the void content or thickness variation. However, the holding parameters, i.e., the holding time and the tool temperature, have very slightly effect on the bending moment of the part, showing that the stamp forming of consolidated plates is a robust process. Using a ten-layer laminate which is 2.5 times as thick as the four-layer laminate leads to mechanical performance six times as good as that of the four-layer laminate. Finally, the first moulding trials of the double curvature door corner shows that, changing the stacking sequence, the blank cutting pattern and the way to hold the blank can greatly improve the part quality.

Date	3 Oct 2016
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Martine Dubé (Supervisor)