Читать книгу Mechanical and Dynamic Properties of Biocomposites - Группа авторов - Страница 19

A natural coconut fiber, also known as coir, is usually extracted from coconut trees. These trees are mainly grown in tropical regions of Asian countries, such as Vietnam, India, and Thailand [4]. Cork fiber is usually obtained from cork oak trees (Quercus suber). There is a specific species of the tree from whose bark the cork fiber is harvested. The cork oak tree is a renewable resource, as new cork bark regrows naturally [4].

Hybrid composites containing high‐density polyethylene (HDPE) with reinforcements of cork powder and short coconut fibers that were randomly distributed was prepared by Fernandes et al. [30]. The interfacial bonding and compatibility between the matrix and fiber was improved by maleic anhydride, a coupling agent (CA). Their results showed 27% and 47% rise in elastic moduli and tensile strengths of the coconut/HDPE/cork hybrid composites, respectively (Table 1.6), when compared with the cork/HDPE composite. Also, they observed that using CA resulted in enhancement of the elongation at break and tensile behaviors of the hybrid composites. As a recommendation for better mechanical responses of the cork‐based composites, 10 wt.% of short coconut fibers and 2 wt.% of CA were proposed.

Table 1.6 Mechanical behaviors of banana/sisal, coconut/cork, coir/silk, corn husk/kenafm and cotton/jute FRP hybrid composites.

Source: Nguyen et al. [4]. © 2017, Elsevier.

Hybrid biocomposites	Fiber ratio (by weight or volume)	Flexural modulus (GPa)	Flexural strength (MPa)	Tensile modulus (GPa)	Tensile strength (MPa)	Impact strength (kJ/m2)
Banana/sisal	100 : 0	8.920	57.33	0.642	16.12	13.25
75 : 25	9.025	58.51	0.662	17.39	15.57
50 : 50	9.130	59.69	0.682	18.66	17.90
25 : 75	9.235	60.87	0.703	19.93	20.22
0 : 100	9.340	62.04	0.723	21.20	22.54
Coconut/cork	10 : 44 : 44 : 2 (wt.% of coconut/cork/HDPE/coupling agent)	—	—	0.599 ± 0.02	20.4 ± 0.3	—
Coir/silk	Alkali treatment
10 mm fiber	—	39.53	—	15.01	—
20 mm fiber	—	45.07	—	17.24	—
30 mm fiber	—	42.02	—	16.14	—
Corn husk/kenaf	0 : 30 (PLA 70 wt.%)	—	—	2.117	—	—
15 : 15 (PLA 70 wt.%)	—	—	1.547	—	—
30 : 0 (PLA 70 wt.%)	—	—	1.221	—	—
Cotton/jute	23.7 : 76.3 (jute fabric type III)
Test angle, 0°	9.9 ± 0.8	136.7 ± 4.0	7.1 ± 0.3	59.4 ± 1.7	9.3 ± 0.9
Test angle, 45°	8.4 ± 0.7	84.6 ± 4.7	4.6 ± 0.1	21.1 ± 1.4	7.5 ± 1.0
Test angle, 90°	7.2 ± 0.7	58.3 ± 5.4	4.1 ± 0.1	14.6 ± 0.5	5.5 ± 1.0

HDPE = high‐density polyethylene.