Evaluation of hybrid-short-coir-fibre-reinforced composites via full factorial design

Abstract

A full factorial design (2 2 3 1) has been used to investigate the effect of the use of sodium hydroxide fibre treatment, Portland cement and uniaxial pressure on the physical and mechanical properties of hybrid short coir fibre reinforced composites (HSCoirFRCs). The response variables considered in this work were the apparent density, porosity, tensile and flexural strength, the modulus of elasticity and the Charpy impact resistance. The alkali treatment contributed not only to reduce the apparent porosity, but also to increase the mechanical properties of the HSCoirFRCs. A reduction of the impact resistance and an increase of the apparent density was also identified after treatment. Cold pressing significantly affected the physical and mechanical properties of the HSCoirFRCs. Higher pressure levels enhanced the wettability of the fibres and, consequently, the mechanical performance of the composites. The incorporation of cement microparticles as a second reinforcement phase was however not effective, leading to decreased strength and an increased apparent density of the materials. The HSCoirFRC structure can be considered an economical and sustainable alternative for future secondary structural parts in lightweight transport applications.

Cold-Pressed Hybrid Composites Reinforced With Coir Fibres and Cement Particles: A Statistical Approach

“…Figure 3b presents the main effect plots for mean tensile modulus. Figure 3b, item a, reveals that the tensile modulus of treated coir fibre composites are 19.34% higher relative to untreated ones, which is attributed to enhanced interlocking as well as an increase in fibre stiffness after the alkaline treatment, as reported by Oliveira et al [22]. Figure 3b, item b, shows a substantial increase in stiffness (65.22%) when cement microparticles were incorporated into the upper beam side and in the whole composite, with no difference between means as shown by the same group A.…”

“…Untreated and treated coir fibre composites present a similar behaviour at all levels (group B), except when the particles were added to the whole sample (group A). This increase of 13.82% is attributed to an increase in stiffness of post-treated fibres [22] as well as of the reinforced matrix phase. This also implies that the particles may play an important role even when added to the lower beam side (under tensile stress), which can be attributed to enhanced interlocking effects.…”

“…Minitab v.17 software was used to perform the Design of Experiment (DoE) and Analysis of Variance (ANOVA) techniques. The constant factors considered in this experiment were established based on a previous work [22]: type of matrix (polyester), fibre grammage (300 g/m 2 ), fibre volume fraction (30%), particle mass fraction (15 wt.%), number of fibre layers per composite plate (3 layers), coldpressing time (22 h), compaction pressure (654 kPa) and curing time (28 days).…”

Evaluation of the stiffening mechanism based on micro-sized particle inclusions in laminated composites

“…A strong interface condition leads to a brittle fracture of the fibres with a consequent reduction in impact resistance. In contrast, a significant portion of the impact energy is dissipated through the thermal energy generated by the friction in the pull-out effect of the fibre, which is more prone to weak bonding interfaces [20][21][22][23][24][25] . In addition, the presence of rigid particles in the composites can also affect their impact behaviour, since it makes the matrix phase stiffer and more brittle.…”

Eco-Friendly Sodium Bicarbonate Treatment and Its Effect on Epoxy/Polyester Coir Fibre Composites

“…As noted, coir fibres led to an increase in tensile modulus and a reduction in tensile strength compared to the neat polymer properties. The increased stiffness is attributed to the coir fibre characteristics, while the reduced strength is relative to the short length and the random orientation of thereof, which hinders the load distribution throughout the sample [25,34,35]. Figure 4, items c and d, shows the second order interaction effect plots for the tensile properties.…”