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Chicken eggshell (Es) waste is an industrial byproduct, and its disposal constitutes a severe environmental risk. Eggshell is a new engineering reinforcement retaining excellent properties such as low density, renewable, eco-friendly, and high thermal stability. The current research aims to study the effects of eggshell particles addition on microstructures, mechanical and tribological properties of aluminium/eggshell green metal matrix composites (MMCs). In the present work Al–Es metal matrix composite is produced by powder metallurgy processes. SEM with EDX and XRD were used to examine the microstructures and the compounds that arise during the sintering process of the produced composites. Six tests were conducted on the produced samples including; dry wear test, micro Vickers hardness, and ultimate compressive strength. The results showed that the addition of 3 wt. % of eggshell improved wear resistance (65%), compressive strength (40%) and hardness (15%). At 6 and 9 wt. % of eggshell, negative results appeared.

Low cost, low density and good thermal stability of hens' eggshells make them a new reinforcement material. Further, eggshell (Es) is considered as a renewable eco-friendly material. Besides, its waste causes insect infestation and therefore pollution problems. Graphite (Gr) is one of the most commonly used reinforcements due to its self-lubricating properties. Hence, the current work aims to use the powder metallurgy technique to fabricate various aluminum matrix composites having different weight percentages of hybrid green particles (eggshells and graphite). Sintering additives such as magnesium and tin were used to improve the density. Firstly, the powders were manually mixed and cold compacted at 475 MPa and then sintered at 630 °C for 2 h. A pin-on-disk wear, Vickers hardness and compressive strength tests were used to investigate the mechanical and tribological properties. Scanning electron microscope (SEM) was used to characterize the morphology and microstructure of the produced composites as well as wear mechanisms. Energy-dispersive X-ray spectroscopy (EDX) test was used to investigate the elemental composition of the composites. The results showed that adding graphite to the aluminum matrix composite containing eggshell has a positive impact on the tribological properties of the composite up to a certain limit (1.5 wt%). However, the additional increase in graphite content has an adverse effect. Hybrid composites with 3 wt% eggshell show the best compressive strength and hardness, whereas hybrid composite with 9 wt% eggshell has the lowest compressive strength and hardness. The mass loss of the hybrid composite increases with the increase in the graphite weight percentages regardless of the eggshell weight percentages. The combination of SEM micrographs and EDX showed signs for three wear mechanisms: abrasive, adhesive and delaminated wear in the examined composites.

The current review extensively discusses the effects of various natural fillers on mechanical, thermal, and tribological characteristics of polypropylene, polyethylene, poly(vinyl chloride), and polyester resin matrices. The discussion has considered all of the tensile, flexural, and impact properties along with the wear rate and thermogravimetric analysis of a wide range of natural reinforcements. Detailed comparative studies about the factors that influence the fillers’ performance in the polymeric composites were also conducted to give the reader a comprehensive understanding to enable a better selection of the optimized characteristics to develop a more sustainable design. This systematic review indicates that the majority of green fillers had an adverse effect on the tensile strength of the considered matrices, but generally improved the tensile modulus. Moreover, the studied fillers enhanced the flexural modulus property for all mentioned matrices. The impact strength was dramatically influenced by the intrinsic characteristic of the filler type.

In this study, the morphological and mechanical performances of hybrid green organic and inorganic filler composites were investigated. Various hybrid reinforcements using natural waste fillers including lemon leaves and eggshells were utilized for the study. The tensile strength, tensile modulus, elongation to break, flexural strength, and flexural modulus were investigated for the composites with polypropylene matrix. The results revealed that eggshells composites had the best values for both tensile and flexural tests while lemon leaves composites had the lowest values. However, the hybrid filler (lemon leaves-eggshells) had intermediate values. The poor properties of lemon leaves were attributed to the agglomeration and weak bonding presented by the morphological analysis of the hybrid composites.