The objective of this investigation was to characterize the performance of natural fiber reinforced polypropylene composites in fused deposition modelling (FDM). Composite filaments comprising of pre-consumer recycled polypropylene with varying contents of hemp or harakeke fibers were extruded from which tensile test specimens were made using FDM. Filament and test specimens were tensile tested and properties were compared with plain polypropylene samples; the ultimate tensile strength and Young’s modulus of reinforced filament increased by more than 50% and 143%, respectively, for both 30 wt % hemp or harakeke compared to polypropylene filament. However, the same degree of improvement was not seen with the FDM test specimens, with several compositions having properties lower than for unfilled polypropylene. SEM analysis of fracture surfaces revealed uniform fiber dispersion and reasonable fiber alignment, but porosity and fiber pull-out were also observed. Fiber reinforcement was found to give benefit regarding dimensional stability during extrusion and FDM, which is of major importance for its implementation in FDM. Recommendations for optimization of processing in order to enhance build quality and improve mechanical properties are provided.

Characterizing the Mechanical Properties of Fused Deposition Modelling Natural Fiber Recycled Polypropylene Composites

Fused deposition modelling is a simple additive manufacturing technology utilising fine filament extrusion of predominantly thermoplastic materials to build 3D objects layer by layer. This research explores the feasibility and the factors involved in using fused deposition modelling to produce natural fibre reinforced composite components. Uniform 3-mm filaments of both hemp and harakeke (Phormium tenax) in varying weight percentages within polylactic acid (PLA) polymer were successfully produced and used to print tensile test samples. Tensile test results supported harakeke to be a useful fibre in terms of mechanical properties achieved which surpassed the Young’s modulus and tensile strength of plain PLA samples by 42.3% and 5.4%, respectively.

Fused Deposition Modelling of Natural Fibre/Polylactic Acid Composites

In the present communication an effective parametric analysis on the mechanical properties (tensile and flexural strength) of bagasse fiber-reinforced vinyl ester (BFRVE) composites were conducted, and then the fabrication process parameters were optimized by using Taguchi and analysis of variance techniques. Composites plates were fabricated by Taguchi’s L18 experimental design as the function of process parameters such as fiber length, fiber content, fiber diameter, sodium hydroxide concentration and sodium hydroxide treatment duration. The optimum process parameters to obtain the maximum strength values were identified using signal-to-noise ratio calculations. Then, the results were analyzed to know the percentage contribution of each fabrication process parameter on the tensile and the flexural strength using analysis of variance. A multivariable non-linear regression model was developed to predict the strength values and compared with experimental strength values. The developed models were validated ...

Parametric analysis of mechanical properties of bagasse fiber-reinforced vinyl ester composites

Replacing glass fibre by natural one in reinforcing engineering plastics for electronic industries has two pre-requirements. Firstly, the processing window should be defined for the engineering plastics of high melting temperature and the natural fibres of limited thermal stability. These processing parameters should be ensured in a stable extrusion procedure. Secondly, a flame retardant (FR) to meet the requirements such as in electronic industries. FR should be however minimised as much as possible to keep good mechanical properties. An optimisation is carried out for extruding thermoplastics like Polyamide 6 (PA6) with natural fibre like flax or kenaf and FR. Extruder configuration is adjusted to obtain a stable process up to 22.5 wt% fibre. Mechanical testing shows just a decrease of 10% in strength and 15–25% in impact strength after the addition of 20% FR.V-0 rating is obtained by 20% FR according to UL94 test. The cone calorimetry shows a reduction in heat release rate HRR to 50% after the application of FR. Also higher share of mineral FR is found feasible keeping UL94 V-0 flame retardance level.

Natural Fibre/PA6 composites with flame retardance properties: Extrusion and characterisation

Hemp fibre-reinforced polycaprolactone (HFRP) composite has inherent good mechanical properties and benefits which include remarkably high specific strength and modulus, low density, and renewability. No doubt, these properties have attracted wider applications of HFRP composite in engineering applications. This paper presents an investigation on the influence of drilling parameters and fibre aspect ratios, AR (0, 19, 26, 30, and 38) on delamination damage factor and surface roughness of HFRP composite laminates utilising high speed steel twist drills under dry machining condition. Taguchi's technique was used in the design of experiment. The results obtained show that increase in cutting speed reduces delamination factor and surface roughness of drilled holes, whereas increase in feed rate causes increase in both delamination factor and surface roughness. Feed rate and cutting speed had the greatest influence on delamination and surface roughness respectively when compared with aspect ratio, while an increase in fibre aspect ratios leads to a significant increase in both delamination factor and surface roughness. The optimum results occurred at cutting speed and feed rate (drilling parameters) of 20 mm/min and 0.10 mm/rev, respectively, when drilling sample of AR 19. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42879.

Effects of drilling parameters and aspect ratios on delamination and surface roughness of lignocellulosic HFRP composite laminates

Natural fibre-reinforced composites have attracted great research and economic interests because of their outstanding
'green' characteristics compared with glass fibre-reinforced composites. It is very important to understand the processing effect on the natural fibre-reinforced composites mechanical properties because of the natural fibre degradation characteristics. Optimizing the fabrication process, especially the compounding process, is effective to achieve the optimal properties of the composites. In this research a natural fibre, noil hemp fibre, was applied to reinforce polypropylene with internal mixing process. The influence of compounding parameters, such as mixing temperature, mixing time and rotor speed, on the mechanical properties (tensile strength, flexural strength and impact strength) of the noil hemp fibre/polypropylene composites was investigated using orthogonal method and the evidence of thermogravimetric
analysis test of fibre and the observation of fibre dispersion in resin. The range analysis and variance of analysis demonstrated that the mixing temperature has significant effect on the three mechanical properties, mixing time has minor influence on the tensile and flexural strengths, and rotor speed mainly affects the impact strength. The thermogravimetric analysis test of noil hemp fibre and the fibre dispersion in resin show that a combination of low mixing temperature, short mixing time and high rotor speed of compounding process is helpful to achieve certain fibre dispersion without serious thermal degradation of fibre. Noil hemp fibre/polypropylene composites with the best comprehensive mechanical properties could be obtained at 165 degree C for 12 min with rotor speed 50 r/min.

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J C Zhang

Papers

Fabrication process optimization of hemp fibre-reinforced polypropylene composites