Polylactic acid (PLA) is a thermoplastic polymer produced from lactic acid that has been chiefly utilized in biodegradable material and as a composite matrix material. PLA is a prominent biomaterial that is widely used to replace traditional petrochemical-based polymers in various applications owing environmental concerns. Green composites have gained greater attention as ecological consciousness has grown since they have the potential to be more appealing than conventional petroleum-based composites, which are toxic and nonbiodegradable. PLA-based composites with natural fiber have been extensively utilized in a variety of applications, from packaging to medicine, due to their biodegradable, recyclable, high mechanical strength, low toxicity, good barrier properties, friendly processing, and excellent characteristics. A summary of natural fibers, green composites, and PLA, along with their respective properties, classification, functionality, and different processing methods, are discussed to discover the natural fiber-reinforced PLA composite material development for a wide range of applications. This work also emphasizes the research and properties of PLA-based green composites, PLA blend composites, and PLA hybrid composites over the past few years. PLA’s potential as a strong material in engineering applications areas is addressed. This review also covers issues, challenges, opportunities, and perspectives in developing and characterizing PLA-based green composites.

Increasing scientific interest has occurred concerning the utilization of natural fiber-enhanced hybrid composites that incorporate one or more types of natural enhancement. Annual natural fiber production is estimated to be 1,783,965 $\times {10}^3$ tons/year. Extensive studies have been conducted in the domains of natural/synthetic as well as natural/natural hybrid composites. As synthetic fibers have better rigidity and strength than natural fibers, natural/synthetic hybrid composites have superior qualities via hybridization compared to natural composites in fibers. In general, natural fiber compounds have lower characteristics, limiting the use of natural composites reinforced by fiber. Significant effort was spent in enhancing the mechanical characteristics of this group of materials to increase their strengths and applications, especially via the hybridization process, by manipulating the characteristics of fiber-reinforced composite materials. Current studies concentrate on enhancing the understanding of natural fiber-matrix adhesion, enhancing processing methods, and natural fiber compatibility. The optimal and resilient conceptions have also been addressed due to the inherently more significant variabilities. Moreover, much research has tackled natural fiber reinforced hybrid composite costs. In addition, this review article aims to offer a review of the variables that lead to the mechanical and structural failure of natural fiber reinforced polymer composites, as well as an overview of the details and costings of the composites.

The interest in using natural fiber reinforced composites is now at its highest. Numerous studies have been conducted due to their positive benefits related to environmental issues. Even though they have limitations for some load requirements, this drawback has been countered through fiber treatment and hybridization. Sandwich structure, on the other hand, is a combination of two or more individual components with different properties, which when joined together can result in better performance. Sandwich structures have been used in a wide range of industrial material applications. They are known to be lightweight and good at absorbing energy, providing superior strength and stiffness-to-weight ratios, and offering opportunities, through design integration, to remove some components from the core element. Today, many industries use composite sandwich structures in a range of components. Through good design of the core structure, one can maximize the strength properties, with a low density. However, the application of natural fiber composites in sandwich structures is still minimal. Therefore, this paper reviewed the possibility of using a natural fiber composite in sandwich structure applications. It addressed the mechanical properties and energy-absorbing characteristics of natural fiber-based sandwich structures tested under various compression loads. The results and potential areas of improvement to fit into a wide range of engineering applications were discussed.

There has been much effort to provide eco-friendly and biodegradable materials for the next generation of composite products owing to global environmental concerns and increased awareness of renewable green resources. This review article uniquely highlights the use of green composites from natural fiber, particularly with regard to the development and characterization of chitosan, natural-fiber-reinforced chitosan biopolymer, chitosan blends, and chitosan nanocomposites. Natural fiber composites have a number of advantages such as durability, low cost, low weight, high specific strength, non-abrasiveness, equitably good mechanical properties, environmental friendliness, and biodegradability. Findings revealed that chitosan is a natural fiber that falls to the animal fiber category. As it has a biomaterial form, chitosan can be presented as hydrogels, sponges, film, and porous membrane. There are different processing methods in the preparation of chitosan composites such as solution and solvent casting, dipping and spray coating, freeze casting and drying, layer-by-layer preparation, and extrusion. It was also reported that the developed chitosan-based composites possess high thermal stability, as well as good chemical and physical properties. In these regards, chitosan-based “green” composites have wide applicability and potential in the industry of biomedicine, cosmetology, papermaking, wastewater treatment, agriculture, and pharmaceuticals.

Recent developments within the topic of biomaterials has taken hold of researchers due to the mounting concern of current environmental pollution as well as scarcity resources. Amongst all compatible biomaterials, polycaprolactone (PCL) is deemed to be a great potential biomaterial, especially to the tissue engineering sector, due to its advantages, including its biocompatibility and low bioactivity exhibition. The commercialization of PCL is deemed as infant technology despite of all its advantages. This contributed to the disadvantages of PCL, including expensive, toxic, and complex. Therefore, the shift towards the utilization of PCL as an alternative biomaterial in the development of biocomposites has been exponentially increased in recent years. PCL-based biocomposites are unique and versatile technology equipped with several importance features. In addition, the understanding on the properties of PCL and its blend is vital as it is influenced by the application of biocomposites. The superior characteristics of PCL-based green and hybrid biocomposites has expanded their applications, such as in the biomedical field, as well as in tissue engineering and medical implants. Thus, this review is aimed to critically discuss the characteristics of PCL-based biocomposites, which cover each mechanical and thermal properties and their importance towards several applications. The emergence of nanomaterials as reinforcement agent in PCL-based biocomposites was also a tackled issue within this review. On the whole, recent developments of PCL as a potential biomaterial in recent applications is reviewed.

Recently, many scientists and polymer engineers have been working on eco-friendly materials for starch-based food packaging purposes, which are based on biopolymers, due to the health and environmental issues caused by the non-biodegradable food packaging. However, to maintain food freshness and quality, it is necessary to choose the correct materials and packaging technologies. On the other hand, the starch-based film’s biggest flaws are high permeability to water vapor transfer and the ease of spoilage by bacteria and fungi. One of the several possibilities that are being extensively studied is the incorporation of essential oils (EOs) into the packaging material. The EOs used in food packaging films actively prevent inhibition of bacteria and fungi and have a positive effect on food storage. This work intended to present their mechanical and barrier properties, as well as the antimicrobial activity of anti-microbacterial agent reinforced starch composites for extending product shelf life. A better inhibition of zone of antimicrobial activity was observed with higher content of essential oil. Besides that, the mechanical properties of starch-based polymer was slightly decreased for tensile strength as the increasing of essential oil while elongation at break was increased. The increasing of essential oil would cause the reduction of the cohesion forces of polymer chain, creating heterogeneous matrix and subsequently lowering the tensile strength and increasing the elongation (E%) of the films. The present review demonstrated that the use of essential oil represents an interesting alternative for the production of active packaging and for the development of eco-friendly technologies.