Abstract
Conventional composite materials reinforced with continuous fibres display high specific strength but have a number of drawbacks including: the elastic-brittle behaviour, difficulties in producing defect-free components of complex shape with high-volume automated manufacturing processes, and inherent lack of recyclability. Highly aligned, discontinuous fibre-reinforced composites (ADFRCs) are truly beneficial for mass production applications, with the potential to offer better formability and comparable mechanical properties with continuous fibre-reinforced composites. In previous publications, the High Performance Discontinuous Fibre (HiPerDiF) technology has been shown to offer the possibility to intimately hybridise different types of fibres, to achieve pseudo-ductile tensile behaviour, and remanufacture reclaimed fibres into high-performance recycled composites. However, to date, the work has been conducted with unidirectional (UD) laminates, which is of limited interest in engineering applications with mechanical stresses acting across many directions; this paper reports, for the first time, the mechanical behaviour of quasi-isotropic (QI) ADFRCs. When compared with randomly-oriented discontinuous fibre composites (RODFRCs), QI ADFRCs offer enhanced stiffness (+26%) and strength (+77%) with higher consistency, i.e., a reduction of the coefficient of variance from the 25% of RODFRCs to the 6% of ADFRCs. Furthermore, hybrid QI ADFRCs retain the pseudo-ductility tensile behaviour previously observed in unidirectional (UD) lay-up.
Highlights
Continuous fibre-reinforced composites achieve high structural performance with minimal weight, replacing metals in many traditional primary and secondary applications in the aerospace sector, but increasingly in wind turbines, automotive structures, and gas and oil pipes [1]
Highly-Aligned Discontinuous Fibre Reinforced Composites (ADFRCs) have the potential to offer mechanical properties comparable with those of continuous fibre composites provided that the fibre aspect ratio is sufficiently high to allow load transfer and attain fibre failure instead of pull-out [3]
In all the aforementioned architectures, pseudo-ductility is achieved through a mechanism comparable to the one described by Jalalvand et al [22]; the stable and progressive fragmentation of low strain-to-failure fibres allows load transfer on to the higher strain-to-failure fibres without the occurrence of global material failure or catastrophic delamination
Summary
Continuous fibre-reinforced composites achieve high structural performance with minimal weight, replacing metals in many traditional primary and secondary applications in the aerospace sector, but increasingly in wind turbines, automotive structures, and gas and oil pipes [1]. In all the aforementioned architectures, pseudo-ductility is achieved through a mechanism comparable to the one described by Jalalvand et al [22]; the stable and progressive fragmentation of low strain-to-failure fibres allows load transfer on to the higher strain-to-failure fibres without the occurrence of global material failure or catastrophic delamination This mechanism has been exploited with continuous fibre thin-ply laminates laid-up in unidirectional (UD) [23] and quasi-isotropic (QI) architectures [24]; the work conducted far to investigate the behaviour of ADFRCs has only been performed on UD laminates and in most engineering applications it is usually necessary to balance the load-carrying capability in multiple directions.
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