and physical characteristics of some natural fibers.
Source: AL‐Oqla et al. [16]. © 2015, Elsevier.
| Fiber type | Coir | Date palm | Flax | Hemp | Sisal |
|---|---|---|---|---|---|
| Density (g/cm3) | 1.15–1.46 | 0.9–1.2 | 1.4–1.5 | 1.4–1.5 | 1.33–1.5 |
| Length (mm) | 20–150 | 20–250 | 5–900 | 5–55 | 900 |
| Diameter (μm) | 10–460 | 100–1000 | 12–600 | 25–500 | 8–200 |
| Tensile strength (MPa) | 95–230 | 97–275 | 343–2000 | 270–900 | 363–700 |
| Tensile modulus (GPa) | 2.8–6 | 2.5–12 | 27.6–103 | 23.5–90 | 9–38 |
| Specific modulus (approx.) | 4 | 7 | 45 | 40 | 17 |
| Elongation to break (%) | 15–51.4 | 2–19 | 1.2–3.3 | 1–3.5 | 2–7 |
Table 1.2 Informative values on the different properties of the fibers.
| Fiber type | Density (g/cm3) | Tensile strength (MPa) | Tensile modulus (GPa) | Elongation to break (%) | Cost per weight (USD/kg) |
|---|---|---|---|---|---|
| Coir | 1.15–1.46 (1.31) | 95–230 (162.5) | 2.8–6 (4.4) | 15–51.4 (33.2) | 0.3 |
| Date palm | 0.9–1.2 (1.05) | 97–275 (186) | 2.5–12 (7.25) | 2.0–19 (10.5) | 0.02 |
| Jute | 1.3–1.49 (1.4) | 320–800 (560) | 8–78 (43) | 1–1.8 (1.4) | 0.3 |
| Hemp | 1.4–1.5 (1.45) | 270–900 (585) | 23.5–90 (56.75) | 1–3.5 (2.25) | 1.3 |
| Kenaf | 1.4 | 223–930 (576.5) | 14.5–53 (33.75) | 1.5–2.7 (2.1) | 0.5 |
| Oil palm | 0.7–1.55 (1.13) | 80–248 (164.0) | 0.5–3.2 (1.85) | 17–25 (21) | 0.3 |
On the other hand, an obvious lack of research regarding the evaluation and selection processes of the natural fiber composites (NFCs) is observed. More specifically, evaluating and selecting the proper agro waste natural fibers for the NFCs is not investigated comprehensively regarding the desired features [9]. Hence, more efforts to establish sufficient comparison criteria are required in order to precisely evaluate and select the appropriate fiber type for the biobased products. The overall characteristics and capabilities of the NFCs depend on the physical, mechanical, chemical, and economic features of the composites' constituents. Therefore, in order to exploit the benefits of these materials to the full extent, comprehensive investigations of the previously mentioned features have to be completed as a primary stage in any industrial application. New techniques have been developed by AL‐Oqla and Sapuan [20] for the assessment and selection of the composites. A wide range of valuable criteria has been discussed by AL‐Oqla and Sapuan [20] to demonstrate that natural fibers have a primary role in natural fiber reinforced polymer composites. Another technique to evaluate various raw fibers was presented by AL‐Oqla et al. [10], where six different types of natural fibers were considered in the evaluation process. These were coir, jute, hemp, kenaf, oil palm, as well as date palm. The physical, mechanical, and economic properties of these types were considered simultaneously. Informative values on the different properties of the considered fibers are listed in Table 1.2. They are obtained from literature based on experimental works, where the average values were adopted assuming that the data is uniformly distributed within the data range found in literature.
Table 1.3 Specific properties of the fibers.
| Fiber type | Specific tensile strength (MPa)/(g/cm3) | Specific tensile modulus (GPa)/(g/cm3) | Specific elongation (%)/(g/cm3) | Cost ratio |
|---|---|---|---|---|
| Coir | 124.05 | 3.36 | 25.34 | 0.231 |
| Date palm | 177.14 | 6.90 | 10.00 | 0.015 |
| Jute | 400.00 | 30.71 | 1.00 | 0.231 |
| Hemp | 403.45 | 39.14 | 1.55 | 1 |
| Kenaf | 411.79 | 24.11 | 1.50 | 0.385 |
| Oil palm |