Influence of flax/polypropylene distribution in twistless thermally bonded rovings on their composite properties

Abstract

Flax has a short fiber length that makes the control of fiber orientation in the composite structure very difficult, which leads to composites with inferior mechanical properties. In order to overcome this difficulty, thermally bonded roving (TBR) with a novel structure where the flax fibers are in a twistfree state and are highly oriented to the roving axis have been developed. In this study, the influence of flax/polypropylene (PP) based TBR structures on their unidirectional (UD) composite properties has been explored. In total, five sets of TBR samples with varying the flax contents (40, 50, and 60 wt% levels) and with varying degrees of flax and PP fiber mixing by changing the number of drawing passages (two times, four times, and six times) have been produced in a specially designed machine. The produced TBR samples are consolidated in a compression molding machine and the resultant unidirectional composites are tested for tensile, flexural, and impact properties. It has been observed that the tensile, flexural, and impact properties of the composite samples improve with increasing flax content and with increasing flax and PP fiber mixing in the roving structure. The present composite samples exhibit better mechanical properties compared to those reported for flax/PP composites in literature. It is mainly due to better fiber orientation and fiber-matrix distribution in the present composite samples.

Effect of cold air plasmas on the morphology and thermal stability of bleached hemp fibers

“…(Macedo et al, 2020a;Alonso-Montemayor et al, 2017). The low intense ν conjugated C=O ) band, characteristic of lignin, appears between 1630 and 1640 cm −1 (Kalia and Kumar, 2013;Araujo et al, 2013;Lu and Oza, 2013;Oza et al, 2011;Bar et al, 2019). Other bands of lignin may appear at 1507 and 1458 cm −1 for C = C bonds and aromatic skeletal vibration, respectively (Macedo et al, 2020b).…”

Influence of hemp roving twist and fiber apparent parameters on the mechanical properties and water absorption of quasi-unidirectional composites

“…As reported in the literature, the twist reduced the ultimate fiber strength in the final composite by a factor of cos2(2 a), where a is the angle of the twist. 25 By decreasing the twist level of the roving, the fibers are more aligned in the mechanical stress direction. The roving twist can reflect the density of the fiber arrangement in the roving and the angle with the roving axis.…”

Towards hemp fabrics for high-performance composites: Influence of weave pattern and features

“…Unfortunately, due to their finite length, it is more difficult to obtain an alignment with plant fibers than with continuous synthetic fibers [12]. Consequently, many studies on plant fiber composites are related to the development and use of different types of reinforcements (unidirectional (UD), non-woven and woven preforms) [2,[13][14][15][16][17][18]. In these studies, the mechanical properties (bending, impact, tensile) are identified at the scale of composite samples, but also at the fibers' scale using back-calculation method from the mixture law, and/or by the IFBT (Impregnated Fiber Bundle Text) method described in [19].…”

“…The main difficulties are associated with the yarn twist, which is necessary in textile technologies to manufacture interlaced fabrics. The twist induces a reduction of the ultimate fiber strength in the final composite by a factor cos²(2α) where α is the angle of twist [15,[20][21][22]. It can also restrict the polymer penetration into the reinforcing fiber bundles [23].…”