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The mechanical, ballistic, and moisture intake properties of luffa fiber reinforced with graphene-modified epoxy composites were experimentally investigated. The nanofiller graphene particles were modified with a matrix using the mechanical stirring process. The filler (graphene) of size 20 nm is modified with the matrix of different weight percentages 0, 1, 2, 3, and 4. The samples for various testings were prepared with different compositions using a hand layup technique followed by compression molding. The results show that tensile, impact, and flexural strength were enhanced with the modification of the filler graphene up to 2 wt%. The ballistic impact results show that energy absorption increases with nanofiller modification. Minimum water intake behavior is observed for the composite samples incorporated with fillers. Failure mechanisms were studied on tensile tested specimens using a scanning electron microscopy. The morphological images showed defects like interfacial behavior, fiber pull out, voids, and internal cracks on the tested specimens. K E Y W O R D S ballistic impact behavior, composite material, graphene, Luffa cylindrica, mechanical properties 1 | INTRODUCTION Owing to their ecofriendly character, low cost, and availability, natural fibers created interest among researchers for producing sustainable polymer composites. [1] As the world is focusing on reducing the effect of greenhouse gasses in the atmosphere, the demand for using natural fibers as reinforcements increased. [2,3] Inorganic fibers like carbon, aramid, and glass fibers have good attractive properties that make them ideal for use as reinforcements in polymer composites. [4] Nevertheless, synthetic fibers suffer from nonbiodegradability, high cost, and hazardous gasses during disposal, which made researchers find new alternative materials. [5] Hence, they tried to use natural fibers as alternative materials to overcome the problems of using synthetic fibers. [4,6] Natural fibers like sisal, [7] banana, [8-11] jute, [12-14] coir, [15,16] luffa, [17,18] hemp [19] and flax, [9,20] and so forth are most commonly used as reinforcements in polymer composites and those materials were used in various interior applications such as furniture, acoustics, vibration isolation, packaging, automobile industries, aeronautical, and marine sectors. [21,22] Their hydrophilic nature reduced compatibility, reinforcing effect, and stress transfer with polymer matrices made the natural fiber composites fit for use in light load and interior applications. The properties and quality of composites depend on the degree of compatibility between the matrix and natural fiber. [23-25] To enhance the bonding between the matrix and fibers researchers used different methods, one of which is surface treatments. Generally, surface treatments like alkali, [3,6,26-28] silane, [29,30] benzoylation treatment, [6,31] and so forth are used for treating the fiber surface. Tolera A. Negawo et al [32] studied the influence of alkali

This study examines the effects of lignite fly ash as a filler on the tribological and mechanical performance of a Calotropis gigantea fiber–epoxy composite. The investigation results show that the Calotropis gigantea fiber/epoxy composite with 2 wt.% lignite fly ash nanofiller added had better tensile strength, interlaminar shear, impact strength, and flexural strength than the control sample by 29.83%, 58.17%, 69.16%, and 11.41%, respectively. The manufactured composite samples were subjected to tribological tests, such as the friction coefficient and specific wear rate under dry sliding conditions with various process variables, such as sliding speed (1–3 m/s), functional load (10, 20, and 30 N), and sliding distance (1000 m). The results show that adding 3 wt.% nanofiller lignite fly ash to the Calotropis gigantea fiber/epoxy composites greatly improves the specific wear rate and friction coefficient. Additionally, the performance of the Calotropis gigantea fiber/epoxy composites in absorbing moisture was enhanced by the inclusion of the nanofiller lignite fly ash 2 wt.%. Likewise, the composite sample developed with the ideal nanofiller lignite fly ash with Calotropis gigantea fiber may be used for sustainable brake materials owing to its superior mechanical and tribological qualities.

Present research work aims to know the significance of nanofiller aluminum oxide (Al 2 O 3 ) loading on viscoelastic behavior and ballistic impact behavior of Kevlar/snake grass fiber (SGF) hybrid epoxy composites. A mechanical stirring process was used to modify the epoxy matrix by adding different weights (0%, 2%, 4%, 6%, 8%, and 10%) of the nanofiller Al 2 O 3 . The manual lay-up method by subsequent hot pressing was used to create the Al 2 O 3 -added Kevlar/SGF hybrid epoxy composites. The tensile, interlaminar shear, flexural, and impact strength were tested. When compared to the control sample, the 2 wt% fillerloaded hybrid composites had higher tensile strength, flexural strength, impact strength, and interlaminar shear strength by 6.42%, 6.11%, 53.11%, and 11.08%, respectively. Furthermore, morphological analysis was performed on the mechanically tested samples to forecast the failure mechanism. The 2 wt% filler-loaded hybrid epoxy composites demonstrated effective interfacial bonding with matrix and minimal fiber pullout, according to micrograph images.The developed hybrid composites were subjected to dynamic mechanical analysis (DMA). The DMA results demonstrated that hybrid composites with 8 wt % filler had better viscoelastic behavior than the control sample. Under a ballistic impact test, the ability of the Kevlar/SGF composites with nano Al 2 O 3 inclusion to absorb energy was assessed. According to the findings, incorporating nano Al 2 O 3 into Kevlar/SGF composites strengthened their ballistic impact resistance and energy absorption. The addition of 8 wt% nanofiller resulted in high energy absorption, according to ballistic impact studies. As compared to the control sample, the composite sample with 8% filler reveals a 68.80% enhanced energy absorption. Furthermore, the composite samples with the optimal wt% Al 2 O 3 nanofiller can be used to mold impact-resistant materials for a bulletproof vest.