Influence of fibre alignments on the mechanical properties of novel Spirograph based non-woven mat composites

Fibre architecture of glass fibre (GF) reinforced polymer composites has a major impact on the mechanical properties for structural applications. In this study, a novel continuous glass fibre non-woven GF mat based on Spirograph art pattern is laid using a customized mechanical system. Spirograph-based continuous glass fibre non-woven (SNW) mat of different patterns was prepared and GF laminate epoxy composites were fabricated with the aim of achieving quasi-isotropic mechanical properties. The samples were cut to dimensions of test specimens from various identical locations symmetrically from a circular-shaped SNW composite laminates which were subjected to flexural, impact, shear and modified compression with anti-buckling tests. One particular SNW pattern composite laminate exhibited 40.82% better impact and 49.01% better shear resistance than commercial 0°/90° woven roving mat composite. The developed SNW laminate composite had quasi-isotropic fibre orientation and better mechanical properties without any stitching and interlacing as in case of woven fibre laminate composite.

Numerical and digital image correlation analysis of tensile behavior of thin-ply hybrid laminates with discontinuous carbon sandwiched by continuous glass and carbon

Thin-ply hybrid laminates of glass and carbon fibers have been widely adopted in engineering pseudo-ductility. In this study, a Finite Element model is proposed using Abaqus to predict pseudo-ductility in thin-ply laminates consisting of three materials. These materials comprise continuous carbon (CC) and continuous glass sandwiching partial discontinuous carbon (DC). The model adopts the Hashin criterion for damage initiation in the fibers and the mixed-mode Benzeggagh-Kenane criterion on cohesive surfaces for delamination initiation and propagation. Numerically predicted stress–strain results are verified with experimental results under tensile loading. Results show pseudo-ductility increases with the increase in DC layers, and pseudo-yield strength and strain increase with the increase in CC layers. 3D-Digital Image Correlation results indicate delamination growth on pseudo-ductile laminates, and the calculated Poisson’s ratios show pseudo-ductility occurs below 0.27. Moreover, Poisson’s ratio decreases with an increase in pseudo-ductility.

3D printed continuous glass fibre-reinforced polyamide composites: Fabrication and mechanical characterisation

Fused Filament Fabrication is a very common additive manufacturing technology and several manufacturers have developed commercial 3D-printers that enable the use of fibre-reinforced filaments in order to improve the mechanical properties of the printed parts. The obtained material is a composite that exhibits complex mechanical properties. The aim of this study is to characterize the mechanical behaviour of 3D-printed continuous glass fibre-reinforced polyamide composites. In a first step, we focus on the reinforced filament: the heterogeneity of its microstructure is evidenced as well as its brittle elastic tensile behaviour. In a second step, parts of different fibre orientations and fibre volume contents are manufactured using a Mark Two 3D-printer (MarkForged®), their microstructure is analysed and tensile, flexural and short beam bending tests are performed. As expected, the results show a significant influence of fibre volume content and fibre orientation. Standard homogenization methods are used to compare the predicted mechanical behaviour to the experimental results. Regarding the elastic stiffness, a good correlation is observed when the material is loaded in the direction of the fibres. Regarding the tensile strength, the results show that no benefit is obtained above a fibre volume content of about 11%. These results highlight the importance of choosing an optimised stacking sequence prior to the printing process, in order to obtain composites with the desired mechanical properties. The mechanical results are analysed in the light of Scanning Electron Microscopy observations of specimen cross-sections before and after testing.