PSI - Issue 66

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Mohammad Jameel Ziedan et al. / Procedia Structural Integrity 66 (2024) 229–246 Author name / Structural Integrity Procedia 00 (2024) 000–000

biodegradable matrix materials such as Poly Lactic Acid (PLA). Various plant fibers such as jute, flax, hemp, and sisal provide distinct qualities for injection molding purposes. Injection molding causes significant fiber breakage, reducing average fiber length significantly. The PNC-IMC merges compounding and injection molding into one step, indicating enhancements in thermal conductivity and cycle time. Parameters such as screw speed, counter-pressure, and extruder length impact Young’s modulus. The research underscores the significance of harmonizing shear energy input and residence time for best outcomes. Incorporating nanofillers boosts thermal conductivity. (Semlali AouraghHassani et al., 2020) emphasize the significance of predicting fiber orientation patterns in short fiber reinforced thermoplastic polymer injection molding to accurately estimate final product properties. Experimental validation demonstrates good agreement for fiber orientation measurements. The research underscores the influence of fiber orientation on material mechanical properties and introduces a theoretical approach utilizing Jeffery's equation to predict fiber orientation under various flow conditions. The study compares the thermal stabilities of sisal and jute fibers, and examines the influence of factors such as fiber content, coupling agents, and distribution on composite properties. Sisal fiber shows superior thermal stability compared to jute, with coupling agents enhancing mechanical properties. Composite impact strength relies on fiber, matrix, and adhesion properties. Energy absorption through fiber breakage, matrix deformation, crack propagation, debonding, and fiber pull-out. Impact strength influenced by fiber content and coupling agent, increasing with fiber content. Composites lacking a coupling agent exhibited higher impact strength. (Barkoula et al., 2010) investigated short and long flax fiber-reinforced polypropylene composites produced by injection molding and various compounding methods. The study evaluated the effect of fiber length reduction during injection molding on mechanical properties, revealing enhanced tensile strength attributed to improved fiber orientation and efficiency. The incorporation of maleic anhydride-PP (MA-PP) further enhanced tensile strength, with kneader-compounded composites demonstrating the highest strength and stiffness. Analysis shows significant fiber breakage during compounding with kinetic mixing and extrusion (see Fig. 17).

Fig. 17. Tensile strength of various methods (28 wt.% flax fibers): (a) kneader, (b) Henschel mixer, (c) twin screw extruder and (d) LFT, (0) unreinforced MA-PP (Barkoula et al., 2010). For almost the same matrix, the impact of injection temperature on the thermal degradation and porosity of bagasse/polypropylene composites during injection molding have been analysed (Shibata et al., 2010). Results showed incomplete filling above 185ºC due to gas accumulation from fiber degradation, with venting improving filling. MAPP composites exhibited improved interfacial bonding, with fibers breaking at their roots, unlike pulled-out fibers in non MAPP composites (see Fig. 18). The adding of wood flour could enhance the strength and stiffness of certain plastics, such as low-density polyethylene (LDPE) and polypropylene (PP). The most effective WPC mix included PP, 47% fine wood flour particles, and 3-4.5% of a coupling agent (MAPP), leading to high tensile strength, bending strength, and storage modulus. By coating the fibers with thermosetting resins, it was able to increase their decomposition temperature and overall properties (Al-Mukhtar et al., 2018). This innovation allowed natural fibers to be incorporated into high-temperature engineering thermoplastics, such as polycarbonate and polyethylene terephthalate, during compression molding. The resulting composites exhibited improved mechanical properties, including flexural strength comparable to glass fiber reinforced polypropylene, see Fig. 19.