Abstract
Discontinuous Long Fibre (DLF) composites, composed of randomly-oriented strands of chopped unidirectional pre-impregnated tape, have been used in the aerospace industry to produce intricate, net-shape parts with complex features – replacing complicated metallic brackets with single, lightweight parts. Carbon/PEEK DLF composites suffer from warpage problems driven by several factors including their high processing temperatures and semi-crystalline matrix shrinkage. This work aims to characterize warpage of thin-gauge parts and pursue mitigation. Results showed that the magnitude of warpage reduces with decreasing strand size and increasing thickness. At thicknesses greater than 2 mm, warpage appeared relatively stable. The introduction of ribbed features was explored as a mean of mitigating warpage by increasing part stiffness. No significant impact on the magnitude of warpage was observed within parts. However, the addition of ribs helped to control the warped shape of the part.
Highlights
The usage of composite materials in aircrafts is dominated by primary structures, such as the fuselage and wing surfaces
The main objective of this work was to advance the knowledge of warpage in discontinuous long fibres (DLF) composites such that critical thickness can be determined in the design stages for DLF parts with large, thin sections and tight dimensional stability requirements
Plates made with short strands warped less than plates made with square strands, leveling out with an average of 0.28 mm warpage for shortstrand parts 2.0 mm and thicker, but still showing between 0.53 mm – 0.68 mm in 3.0 mm thick parts made with square strands
Summary
The usage of composite materials in aircrafts is dominated by primary structures, such as the fuselage and wing surfaces. Demand for compression-moulded DLF composites is growing in the aerospace industry and manufacturers like Greene Tweed[9,10] have demonstrated its potential for commercial use. One such example is the XycompVR DLF carbon fibre/Polyether-ether-ketone (PEEK) bracket,[9] a 43% lighter single-piece replacement for a three-part aluminum assembly. In creating this near net-shape part as one piece, manufacturing time is significantly reduced, lowering part cost as well as part weight
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
