Influence of Fibre Treatment and Matrix Modification on Mechanical Properties of Flax Fibre Reinforced Mortars after Freeze/Thaw Cycles

The aim of this study was to examine the influence of flax fibre protection with the linseed oil and a matrix modification with cement substitution with metakaolin (in 10wt% and 15wt%) on the mechanical properties of cement-based mortars under severe environmental conditions of freeze/thaw cycles. Cement-based mortars (with the dimension of 40x40x160 mm3) were reinforced by 10mm long discrete flax fibres (Linumusitatissimum) and exposed to 51 freeze/thaw cycles under laboratory condition. Their compressive and flexural strengths, as well as specific energy absorption capacity were measured after freeze/thaw cycles and compared to the results of mortars cured for same time in water. Under freeze/thaw cycles mortars reinforced with linseed oil-treated fibres showed the same range of degradation of the compressive and flexural strengths, however, a more pronounced degradation of energy absorption capacity compared to non-treated fibre reinforced mortars was observed. The matrix modification, by partial cement substitution with metakaolin showed optimistic results under freeze/thaw cycles. The compressive strength when cement was partially substituted with metakaolin (in both dosages) increased whereas the flexural strength was slightly lower in case of 10wt% substitution and markedly lower under higher (15wt%) cement substitution. The most relevant is that the decrease of the energy absorption capacity of the fibre reinforced mortar was completely prevented when cement was substituted with metakaolin. It is shown that the energy absorption of the non-treated fibre reinforced mortars increases by 27% when cement was substituted with metakaolin (both 10wt% and 15wt%).

Influence of Flax Fibre Hybridization on Mechanical Behaviour of Sisal Fibre-Polypropylene Composites Prepared with an Injection Moulding Machine

Due to their low weight, high specific strength, and low environmental impact, sisal fibre-polypropylene composites have gained popularity. However, the material has a low modulus and poor moisture resistance, among other shortcomings. This study investigated how flax fibre hybridization affects the physical parameters of sisal fibre-polypropylene composites. We used maleic anhydride-grafted polypropylene to improve compatibility between fibres and polypropylene. Adding flax fibres to polypropylene-silica composites resulted in increased tensile strength, flexibility, and impact strength, according to researchers. Water resistance was further improved by adding flax fibres. Tensile strength values of polypropylene-sisal fibre composites filled with 0, 5, 10, 15, and 20 wt% of flax fibres were 29.46, 30.56, 31.57, 33.12, and 34.64 MPa, respectively.

Vacuum Infusion Simulation for Radome Manufacturing Using Woven Flax Fibre and Glass Fibre

The vacuum infusion method is emerging to produce composite parts, especially thin wall structure aircraft radome. Ansys Fluent is used in the optimization phase for mould filling analysis on aircraft radome part. The permeability fibre is referring to the physical property of the fibre reinforcement to allow fluids to permeate it, thus it is correlated with the viscosity of the resin used. In this work, flax fibre, glass fibre and low viscosity epoxy resin are used to determine the permeability value of flax fibre, glass fibre and hybrid without using a flow medium. In-plane experiment on reinforcement fibre permeability is conducted and all reinforcement fibre have similar fibre architecture and weight. The development of a digital model from a top partial aircraft radome is obtained through a 3D scanner and CATIA. Ansys Fluent is used to optimize the location of the injection line and air vent for the epoxy. The Ansys Fluent analysis model is validated through the in-plane experiment filling time result for a flat model. Based on the simulation analysis, the location of the injection line is placed at the perimeter and the air vent at the centre. The filling time from the simulation for the flax fibre and hybrid fibre was estimated around 10 to 11 minutes. However, the filling time for glass fibre is approximate 2 hours which is longer than epoxy gel time. Furthermore, this method can be used in mould filing scenarios of thin wall structure within gel time of the resin.

Effect of Printing Parameters on Mechanical Behaviour of PLA-Flax Printed Structures by Fused Deposition Modelling

Few studies have reported the performance of Polylactic acid (PLA) flax feedstock composite for additive manufacturing. In this work, we report a set of experiments conducted by fused filament technology on PLA and PLA-flax with the aim of drawing a clear picture of the potential of PLA-flax as a feedstock material. Nozzle and bed temperatures are both combined with the printing angle to investigate their influence on structural and mechanical properties. The study shows a low sensitivity of PLA-flax to process parameters compared to PLA. A varied balance between shearing and uniaxial deformation is found consistent with tensile results where filament crossing at −45/+45° provides the optimal load-bearing capabilities. However, Scanning Electron Microscopy (SEM) and high-speed camera recording shows a limiting reinforcing effect of flax fibre due to the presence of intra-filament porosity and a significant amount of fibre pull-out resulting from the tensile loading. These results suggest that the quality of the bond between PLA matrix and flax fibre, intra-filament porosity, and surface roughness should receive more attention as well as the need for more continuous fibre reinforcement in PLA filaments to optimise the performance of PLA-flax printed materials.