Compression moulding of composites with hybrid fibre architectures

Abstract

Advanced Sheet Moulding Compounds (ASMC) and unidirectional (UD) prepregs have been co-compression moulded to form a hybrid composite material. In-mould flow influences the UD fibre architecture in two ways. When UD fibres are aligned transversely to the ASMC flow direction, shearing occurs which causes local changes in fibre volume fraction and fibre waviness. When the UD fibres are aligned with the ASMC flow direction, ply migration takes place. In general, the composite stiffness follows a rule of mixtures relationship, with the stiffness proportional to the UD fibre content.A grid analysis method has been developed to quantify distortion in the UD plies. Staging the resin to 50% cure was shown to reduce ply distortion during moulding, whilst maintaining suitable inter-laminar shear strength. Adding an interfacial prepreg ply between the reinforcing UD fibres and the ASMC charge successfully prevented distortion in the UD fibres, avoiding shear thinning and fibre migration.

Mechanical characterisation and modelling of randomly oriented strand architecture and their hybrids – A general review

“…(a) Ply distortions in hybrid specimens with and without interfacial ply between SMC and UD plies; 28 (b) T-shaped parts with and without the flow-control element. 25 …”

“…Hybrids demonstrated reduced warpages. In a study focused on the flow and mechanical properties of ROS-hybrids, Corbridge et al 28 used HexMC with 50 mm fibre length, and UD prepregs under high flow compression moulding. Using a grid strain method, quantitative analysis of the distortion of the UD fibres in terms of translations and rotations was determined.…”

“…Benefits of hybridisation include: improved and tailored modulus properties, reduction in the variability, and better control over the failure initiation, damage and propagation. 13,24–29 In addition, hybrid fibre architectures allow for better predictability of failure and strength in notched specimens, 26 increase in the interlaminar properties, and reduction in warpage and reduction of swirling of strands. 25 Although the main goal of hybrid fibre architectures is to obtain reinforcing effects, the use of such systems could lead to synergistic behaviours.…”

Process Optimization for Compression Molding of Carbon Fiber–Reinforced Thermosetting Polymer

“…The CFRTP can be molded through compression molding, autoclaving, winding, or pultrusion [6,7,8]. Compression molding stands out for its low cost, high efficiency, low internal stress, small buckling deformation, good mechanical stability, and excellent product repeatability [9]. Unsurprisingly, this molding method boasts a strong competitive advantage in industrial mass production of parts and components, and the advantage grows with the production volume.…”

An evaluation of three different techniques for melt impregnation of glass fiber bundles with polyamide 12

“…Van Der Klift et al [15] and Melenka et al [16] performed mechanical tests on respectively continuous carbon fiber and aramid fiber filled polyamide tensile specimens created by this apparatus and showed that the technique is able to produce high strength parts, when compared with regular thermoplastic AM parts. Yet, fiber volume fraction V f was reported to be only 34.5% [15], which is rather low compared with typical volume fractions of $55%-60% for unidirectional AFP and ATL produced material [17,18] or $60%-80% for traditionally compression molded unidirectional composites [19].…”