Natural unidirectional sheet processes for fibre reinforced bioplastics

Abstract

Abstract. Technical natural fibre semi-finished products are mainly used in lightweight automotive components as random fiber mats which are often combined with petrochemical matrix resins for large series production process. However, random fiber arrangement and limited fiber length restrain the complete utilization of the material-inherent strength reserves of natural fibers. With high-levels of petroleum-based plastics (about 20-50 wt -%) in the structure, these applications have a clear potential in terms of eco-friendliness and sustainability. The development of new fully bio-based composites and efficient manufacturing methods suitable for series processing is the purpose of the current sub-project C4 "Flexible textile / plastics processes with renewable raw materials" in the framework of the Excellence Cluster MERGE EXC 1075, funded by DFG (Deutsche Forschungsgemeinschaft). A high-efficiency in terms of massproduction, reproducibility and flexibility requires the performance of successive steps in the manufacture of semifinished and final products. The appropriate process line comprises the steps of the preparation of the thermoplastic matrix sheets (such as from Bio-polyethylene or Bio-polyamide) and a specific chemical modification of the reinforcing materials (wood veneer and unidirectional flax fibers) on the concept of a discontinuous or continuous production of unidirectional reinforced Natural Fibre Composites (NFC) prepregs. Moreover, the shaping of hybrid lightweight structures from NFC prepregs makes possible the incorporation of these innovative technologies into new concepts and potential applications in several fields such as automotive industry or sport equipment. The mechanical properties profile of the flax -natural unidirectional sheet for fibre reinforced bioplastics has been here studied in detail with pressengineered samples and has confirmed their high application potential as an alternative to glass fiber-reinforced composite sheets.

A Review on the Fabrication and Mechanical Characterization of Fibrous Composites for Engineering Applications

“…This weakness can be attributed to the detachment of the outer layer and individual fibers in contact with the matrix during compounding and extrusion, which is not caused by a lack of physical and chemical compatibility between the fiber and matrix. A study by Ouali et al [111] showed that a high-density polyethylene composite made with a 40% kenaf fiber mat had similar mechanical properties to a composite made with 40% discontinuous glass fiber and HDPE. Both composites had specific tensile strengths and moduli, as well as flexural strengths and moduli.…”

Thermoplastic Hybrid Composites with Wood Fibers: Bond Strength of Back-Injected Structures

“…A rare scientific publication on back-injection of natural fibers is Ouali et al, who analyze the back-injection of prepregs with unidirectional flax fibers. They focus on the continuous production of prepregs with biopolymers and their mechanical behavior and only show images of back-injected structures, but do not mention their bond strength [ 51 , 52 , 53 ].…”

Degradable, Lightweight, and High-Performance Unidirectional Nanocellulose-Long-Filament-Reinforced Vanillin Epoxy Composites for Structural Applications

“…The ease of manufacturing associated with unidirectional prepregs also offers customized layups for the tailored mechanical performance of the composite materials. In the past, various unidirectional NFRGCs have been analyzed. ,,, UD-NCLF especially offers precise fiber alignment for directional properties by maximizing the structural benefits inherent in nanocellulose-based materials. Figure shows the fabrication process of the UD-NCLF-VE green composite.…”

“…17 However, a few thermosetting resins demonstrated better adhesion with natural fibers compared to thermoplastic resins due to crosslinked networks such as ramie-fiber-reinforced soy protein resin. 18,19 Nevertheless, robust interface adhesion remains a big challenge for NFRGCs because of the noncompatibility of natural fibers and resins due to the lignin and hemicellulose content in natural fibers. 20−23 This study reports the utilization of a unidirectional NCLF (UD-NCLF) with biobased vanillin epoxy (VE) resin for a unidirectional NCLF-reinforced VE (UD-NCLF-VE) green composite from the diverse feedstocks of lignin and cellulose.…”

“…In the past, various unidirectional NFRGCs have been analyzed. 15,16,18,19 UD-NCLF especially offers precise fiber alignment for directional properties by maximizing the structural benefits inherent in nanocellulose-based materials. Figure 1 shows the fabrication process of the UD-NCLF-VE green composite.…”