Relationships between skin follicle characteristics and fibre properties of Suri and Huacaya alpacas and Peppin Merino sheep

We aimed to quantify the number, type and arrangement of skin follicles in Huacaya and Suri alpaca skin and correlate their follicle characteristics with fibre traits of harvested fibre and compared these relationships with those of Merino sheep. Fibre and skin samples were collected from the mid-side of 12 Huacaya alpacas, 24 Suri alpacas and 10 Merino sheep. The mean fibre diameter (MFD ± s.e.) of the Huacaya and Suri were: 35.5 ± 0.9 and 28.3 ± 1.0 μm, respectively. The follicle groups found for alpacas were very different from the normal trio of primary follicles found in sheep and goats. The follicle group of the alpacas consisted of a single primary follicle surrounded by a variable number of secondary follicles. The mean ± s.e. primary follicle density was 3.1 ± 0.3 and 2.7 ± 0.1 follicles/mm² for Huacaya and Suri, respectively. The mean ± s.e. secondary follicle density (SFD) was 13.7 ± 1.2 and 17.5 ± 0.6 follicles/mm² for Huacaya and Suri, respectively. The mean ± s.e. ratio of secondary to primary follicles (S/P ratio) was 5.1 ± 0.5 for the Huacaya and 7.3 ± 0.2 for the Suri alpacas. The sheep had higher S/P ratios and SFD, lower MFD and produced significantly heavier fleeces. The key correlations found between traits in alpacas include a negative correlation between SFD and MFD (r = –0.71, P = 0.001) and a negative correlation between S/P ratio and MFD (r = –0.44, P = 0.003) and a positive correlation between S/P ratio and total follicle density (r = 0.38, P = 0.010). The study revealed that important relationships exist between alpaca skin follicle characteristics and fibre characteristics. It was the number of secondary follicles in a group that imparts density and a corresponding reduced MFD.

Fibre properties affecting the softness of wool and other keratins

The emerging market for next-to-skin knitwear requires wool to satisfy the consumer’s tactile requirements for softness. The role of the fibre’s surface and physical properties on fibre and fabric softness was examined. The fibre’s cuticle properties were found to have a greater influence on softness than the fibre’s mechanical properties.

Measuring the influence of fibre-to-fabric properties on the pilling of wool fabrics

This study ranks the contribution of various fibre, yarn and fabric attributes to the pilling of wool knitwear. On the basis of an artificial neural network modelling, a combination of sensitivity analysis, forwards/backwards search and genetic algorithms was used to identify the importance of various fibre/yarn/fabric input parameters. The three different techniques show broad similarities in their assessment of which input parameters are important or are not important in affecting fabric pilling. The ranking shows that fabric cover factor has the most effect on pilling, followed by yarn count and thin places, fibre length, yarn twist, etc. It is further illustrated that the directional trend of the predicted pilling outputs for a selection of inputs was in line with the expected behaviour. To verify the findings of input feature selection, input factors deemed to have a small effect on the predicted pilling output, such as fibre length and diameter variations and curvature, were removed and the subsequent performance statistically compared to the original multi-layer perceptron. Differences between the outputs predicted by the original and pruned models are found not to be statistically significant at the 5% significance level. Results from this study may help manufacturers and knitwear designers in choosing the most appropriate materials and structures to reduce the pilling propensity of wool knitwear.

Eri silk fibre attributes and sliver preparation

Eri silk produced by Philosamia cynthia ricini silkworm is a fibre not well-known to the silk industry, in spite of the fact that Eri silk is finer, softer, and has better mechanical and thermal properties than most animal fibres. Eri silk has a high commercial potential, as the host plants of Eri silk worms are widespread in diverse geographical locations, and the worms also have a higher degree of disease resistance than most other silk worms. Mills are often not aware of the properties of Eri for designing appropriate end products. Thus, Eri silk yarn is traditionally produced by hand spinning, and Eri silk usually ends up as material for handwoven shawls. The potential for bulk fibre processing and the development of soft luxurious novel Eri silk products is yet to be discovered. To better understand the material and its processing behaviour, Eri silk was characterised and cocoons were processed into tops through degumming, opening, and cutting filaments into different lengths, followed by a worsted spun silk processing route. Fibre properties such as fineness, crimp, strength and length at different processing stages up to combed tops were measured. The results indicate that staple Eri silk can be processed via the worsted topmaking route, using a cut length of 200 mm or 150 mm for filament sheets prepared from degummed cocoons.

Cuticle modifications and dyeing property of ultrasonically scoured wool

Ultrasonics has the potential to reduce the cost and environmental impact of textile processing. This work investigates the effects of utrasonic irradiation during wool scouring on fibre surface properties and fibre dyeing rate. A range of ultrasonic frequencies were used in the scouring bath to examine the forms of fibre cuticle damage. It was shown that ultrasonically scoured wool underwent some modifications of the fibre surface structure which resulted in a higher rate of dye uptake by the fibres, when compared with the conventionally scoured wool. The lower the ultrasonic frequency the more sever was the cuticle damage to wool during scouring, hence the higher the fibre dye uptake.

Frequency dependence of ultrasonic wool scouring

Conventional aqueous scouring of greasy wool promotes wool felting and can be energy and water intensive. Ultrasonic wool scouring could be an alternative technology to minimise the negative impact, provided that the cleaning efficiency and fibre quality are not compromised. This study  examined the influence of ultrasonic irradiation frequency and ultrasonic power variations on wool scouring performance at different liquor ratios. Scoured fibre, residual ash content, residual grease content, whiteness and yellowness were evaluated. The impact of liquor degassing on wool scouring effectiveness was studied. Fibre surface damage was also assessed in this work. It was observed that while there was no significant influence of ultrasonic frequency on the whiteness or yellowness of the scoured fibres, wool scoured at frequencies of 28 kHz and 80 kHz had more grease and dirt removed than that scoured at 45 kHz. Low ultrasonic power and degassed bath liquor increased wool grease removal ability. Ultrasonic treatment caused scale cracking/peeling in some wool fibres. More severe cuticle damage was observed in fibres scoured at the lower frequency. This damage resulted in increased dye uptake by the fibres.

Study into the ultrasonic cleaning of wool

This research studied the use of ultrasonic irradiation during wool cleaning with an aim to improve the cleaning process and reduce its impact on the environment. The research found that ultrasonic cleaning reduced energy, detergent and chemicals consumption, reduced fibre entanglement and had no significant effect on fibre properties.

Effect of surface functionality of PAN-based carbon fibres on the mechanical performance of carbon/epoxy composites

The performance of composite laminates depends on the adhesion between the fibre reinforcement and matrix, with the surface properties of the fibres playing a key role in determining the level of adhesion achieved. For this reason it is important to develop an in-depth understanding of the surface functionalities on the reinforcement fibres. In this work, multi-scale surface analysis of carbon fibre during the three stages of manufacture; carbonisation, electrolytic oxidation, and epoxy sizing was carried out. The surface topography was examined using scanning electron microscopy (SEM), which revealed longitudinal ridges and striations along the fibre-axis for all fibre types. A small difference in surface roughness was observed by scanning probe microscopy (SPM), while the coefficient of friction measured by an automated single fibre tester showed 51% and 98% increase for the oxidised and sized fibres, respectively. The fibres were found to exhibit heterogeneity in surface energy as evidenced from SPM force measurements. The unsized fibres were much more energetically heterogeneous than the sized fibre. A good correlation was found between fibre properties (both physical and chemical) and interlaminar shear strength (ILSS) of composites made from all three fibre types. © 2014 Elsevier Ltd.

Properties of hemp fibre reinforced concrete composites

This research is concerned with the mechanical and physical properties of hemp fibre reinforced concrete (HFRC). An experimental program was developed based on the statistical method of fractional factors design. The variables for the experimental study were: (1) mixing method; (2) fibre content by weight; (3) aggregate size; and (4) fibre length. Their effects on the compressive and flexural performance of HFRC composites were investigated. The specific gravity and water absorption ratio of HFRC were also studied. The results indicate that the compressive and flexural properties can be modelled using a simple empirical linear expression based on statistical analysis and regression, and that hemp fibre content (by weight) is the critical factor affecting the compressive and flexural properties of HFRC.

The mechanical properties of natural fibre reinforced cementitious composites

This thesis examined the mechanical properties of natural fibre reinforced cementitious composite materials. The results have provided essential data for the design of these composite materials for different applications. The theoretical model developed also allows accurate prediction of composite behaviour under different loading conditions.

High strain rate tensile properties of rapidly cured woven carbon fibre composites

Tensile tests at high speeds corresponding to automotive crash events were conducted to understand the dynamic properties of rapidly cured woven carbon fiber composites. The High Strain Rate (HSR) experiments were conducted on a servo-hydraulic machine at constant velocities up to a maximum of 25 m/s (82 ft/s). Results from HSR tests were compared with the static results to determine the rate sensitivity of the composite. A high speed camera was used to capture the failure at HSR. The tensile properties of rapidly cured laminate were compared to oven cured laminate to justify its productivity while maintaining the desired properties. The methodology used to achieve constant velocity during HSR tests is discussed in detail. The specimen geometry was specially designed to suit the test rig and to achieve high speeds during tests. All the specimens failed with linear elasticity until sudden brittle fracture. The Scanning Electron Microscopy (SEM) images of the fracture zone were used to identify the failure modes observed at static and high strain rates.