1. Study of Mechanical Properties of Natural and
Hybrid Fibres Reinforcements
*Aina Bernava 1, Maris Manins 2, Guntis Strazds 3
1-3 Forest Industry Competence Centre, Dzerbenes Street 27, Riga, LV-1006, Latvia
INTRODUCTION
The interest in natural fiber-reinforced polymer composite materials is rapidly growing in industrial applications and fundamental research. They are renewable, cheap, completely or partially recyclable, and biodegradable. Natural fibers are increasingly used for the reinforcement of composites in transportation, military applications, building and construction industries, packaging, consumer products, etc. [1] Production of natural fibers mainly depends on solar energy, fiber pre-processing and processing requires relatively small amounts of fossil fuels. Energy requirements are 54.7 MJ/kg for production of glass fibers and 9.55 MJ/kg for flax fibers [2] while the price of polymer composites reinforced with natural fibers is times lower than that of polymers reinforced with glass fiber [3]. 30,000 t natural fibers (17% flax and 5% hemp of total volume 80,000 t) in 2012 year were produced in the EU Automotive Industry [4].
MATERIALS AND METHODS
Hemp yarns with the yarn density 100 tex (HA-1; Germany) and 1186 tex (HA-2; Latvia), flax yarn of 678 tex (LI; Latvia) and hybrid yarns of glass /hemp fibers 1644 tex (GF; JSC, Valmieras stikla skiedra, Latvia] were used (Table1). For production of samples in 2D weaving technique the industrial loom CTБ-175 (Soviet Union) was used. . Tensile strength, tensile elongation and tensile stress of reinforcement of hemp, flax and hybrid yarns in warp and weft directions were tested corresponding to LVS EN ISO on INSTRON dynamometer (Intron Ltd, UK). Measurements of fabric thickness were carried out by ATLASS thickness meter (SDL Atlas Inc. USA), according ASTM D1777 – 96(2011) e1standard.
Fig.1. Woven structures of HA-1 yarns (A) and HA-2(B) on both directions; hybrid structures of HA-2 on warp direction and GF/HA yarns (C) as well as flax yarns (D) on weft direction.
Table 1.Yarns Used and Physical-Mechanical Properties
Fiber
Hemp
Flax
Glass Fiber/ Hemp
Designation
HA1
HA2 LI GF
Yarn density [tex]
100
1187
678
1644
Maximum load [N]
15.46
134.16
87.87
110.45
Tensile extension [mm]
17.31
19.20
18.48
4.50
RESULT AND DISCUSSION
Woven 2D structures (Fig.1 Table 2) of natural hemp [A, B] and flax yarns [D] as well as hybrid yarns [C] of glass and hemp fibers were produced in plain weaving technique. Fabric surface parameters ( Table 2) and phisical- mechanical properties were tested and results can seen on Figures 2-5.
Figure 2. Tensile Strength [N] of woven reinforcements
Table 2 Materials Use and Surface Parameters of Reinforcements
Thread type
Hemp
Flax
Glass Fiber/ Hemp
Fabric surface parameters
Designation
HA1
HA2 LI GF
Fabric thickness [mm]
Surface density [g/m2]
Direction
Warp
Weft
Threads density [10 cm] A 50 42
0.61 83 B 25 37
2.37
529 C 26 27
2.52
769 D 67
2.45
738
Figure 3. Tensile Stress [MPa] of woven reinforcements
Figure 4. Tensile Modulus [MPa] of woven reinforcements
Figure 5. Extension [mm] of woven reinforcements
CONCLUSION
Nowadays a lot of attention is paid to environmentally friendly materials. Woven structures of the hemp yarns and the hybrid structures of hemp yarns interwoven with the flax yarns or hybrid yarns of hemp and glass fibre were produced. The values of the tensile strength and the tensile stress on both directions are higher for reinforcements with use of high density hemp yarns on the warp direction, while on the weft direction they are higher for all reinforcements. On the contrary, the highest tensile modulus on both directions is for the reinforcement of low density hemp yarns, and on the warp direction for the reinforcement of high density hemp yarns. The smallest elongation could be achieved on both directions by using hemp yarns of low density, but for all reinforcements of natural fibres extension on the weft direction is high. Finally, small elongation and high tensile strength of reinforcements of natural fibres are the most important aspects to ensure that the parameters of the composite material are stable.
REFERENCES
[1] Singh A., Vishvendra Meena S., Study of Mechanical Properties of Hybrid Natural Fiber Composites (A Thesis for Degree of Bachelor of Technology In Mechanical Engineering, Rourkela, 2011).
[2]Bast and Other Plant Fibres Edited by Franck R.R. (Woodhead Publishing Ltd, 2005, pages1-376).
[3] Wladyka-Prybylak M. Bujnovicz K., Natural Fibres Reinforced Polymer Composites (Presentation of Workshop FP7 -Research and Development Programme for Advanced SMEs, Zagreb, )
[4] Carus M. World-wide Market Data on Hemp and Other Bast Fibres (Presentation of11th EIHA conference, Wesseling, )