**3.1. Automobile applications**

biodegradability of PLA-wheat straw and PLA-soy straw-based green composites. The result of this study elucidates that under aerobic composting the soy and wheat straw degraded rapidly over 70% within 45 days. The similar result obtained in the process of composites degradation irrespective of the biomass used, this rate of degradation was higher than that of pure PLA. Indeed, the faster rate degradation in composites may be due to the presence of degradable natural biomass in composites and due to reduced average molecular weight of PLA [33]. Lu et al. observed the biodegradation behavior of PLA/distiller's dried grains with soluble (DDGS) composites. These materials consist of bio-based and strong potential for industrial applications. The composites were made by adding 20% DDGS to the 80% of PLA and biodegradation experiments were conducted in soil under landscape conditions. The result of this experiment shows that during 24 weeks of degradation time the weight loss of the composites was 10.5%, while the weight loss of pure PLA was only 0.1% during the same time interval. With increasing the degradation time, the surface cracks and voids caused by erosion and loss of polymer chain length were clearly observed as shown in **Figure 11** [34]. The untreated and treated with acetic anhydride-treated (AA-) abaca fibers were reinforced with aliphatic polyesters (poly (ϵ-caprolactone) (PCL), poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), PBS, and PLA). The biodegradability of obtained composites was studied by the soil-burial test. The result of the test reveals that the presence of abaca fiber or AA-abaca did not show any effect of weight loss on PCL composites, because PCL itself has a relatively high biodegradability. However, the addition of abaca fibers was shown to accelerate the weight loss of PBS and PHBV composites. Moreover, no weight loss was observed in pure PLA and PLA/AA-abaca composites, but PLA/untreated abaca composites showed 10% weight loss after 60 days due to degradation of fiber by microbial activity [35]. Yussuf et al. [36] investigated the biodegradability difference between PLA/kenaf fibers (KF) and PLA/rice husk flour (RHF) composites by natural soil burial test. The result of this test elucidates that the biodegradability of these composites slightly increased and reached 1.2 and 0.8% for PLA-KF and PLA-RHF, respectively, for a period of 90 days. Moreover, this percentage change in biodegradability of composites is higher as compared to pure PLA, because microorganisms are easily attacked in the presence of natural fibers [36]. Another study emphasized the effect

190 Composites from Renewable and Sustainable Materials

**Figure 11.** SEM micrographs of PLA/DDGS 80/20 composites after 0, 8, 16, and 24 weeks. Biodegradation time

dependence of weight loss of pure PLA and PLA/DDGS (80/20) composites in soil medium [34].

The usage of the biocomposite makes the car lighter, renders greater resistance to heat, external impact, and improves fuel capacity. This leads further to manufacture mid-end and low-end cars as well. The pioneering research on composites and large mass production techniques forced to decline the prices and increase demand for various applications including the automotive sector [39].

Akampumuza et al. [2] reviewed the application of biocomposites in the automotive industry. In this review, they identified future significance of biocomposites in the automotive industry through bioconcept cars. Though these seldom make it to the market, they are useful to give an idea to the industry on the possibilities of particular materials and designs. In 2001, Toyota Motor Corporation brought eco-friendly model an ES3 concept car made with polyester reinforced with hemp fibers composite parts such as carpets, lightweight seats, body panels, and other interior parts exhibited to give awareness of this cleaner manufacturing process. With this inspiration and response in 2003, they bring another model Toyota Raum, which had its interior parts made by using hemp fibers and its springboard was made from potatoderived PLA reinforced with sugarcane bagasse. In 2008, at British Motor Show in London, U.K.-based Lotus car displayed lotus Eco Elise green technology with aimed at making the use of eco-friendly materials and a cleaner manufacturing process in accordance to achieve weight and carbon miles reduction with the features of components made from bioplastic and biofibers such as sweet potatoes and sugarcane. Renault has been developing a series of bioconcept cars for the racetrack with the first generation introduced in 2006. Volkswagen Scirocco a bioconcept car was configured as a racing car. Several parts of the car body such as the rear hatch, the driver's door, and the front lid have been produced by eco-friendly materials by compression molding. In March 2014, at 84th Geneva International Motor Show, UPM Company displayed biofore concept car with the collaborated Helsinki University of Applied Sciences. The improved manufacturing methods and brilliant technology drive the car's weight reduction by more than 15%. The researchers believed that the biofore car would be the role model for the advance development in manufacturing and technology of actual car making [2]. Four Motors GmbH of Reutlingen, Germany, was presented with the composites in the third generation of bioconcept cars in 2015, which has an extremely efficient TDI engine and travels with a novel, low-pollutant biodiesel based on rapeseed oil. The lightweight body is made from a reinforced natural fiber thermoset, and other components in the interior and the engine compartments are made from bio-based plastics [40].

#### **3.2. Marine applications**

Several researchers discovered that the biocomposites have potential marine applications due to their good mechanical properties and biodegradability. Due to these properties, the biocomposites become an alternative to the synthetic fiber-reinforced composites. Le et al. [41] conducted the experiment on seawater aging of flax/PLA biocomposites. The obtained result of this experiment describes that under seawater aging mechanism the absorption of water determined the degradation of hydrolysis of the matrix, structural change, degradation of the fiber/matrix interface, different swelling at composite interfaces and the degradation of fibers reduced the mechanical properties of the composites. However, the matrix and fiber cracks also appear at longer periods. This accomplishes that a special care is needed to integrate marine structures due to biodegradable nature of biocomposites. Indeed, with the eco-friendly impact of usage recyclable materials, now the extensive research is continuing in this area for optimizing lifetime, degradation control, and inherent losses of properties [41]. In the similar study, for the innovation in sailing yacht design must include the current environmental concerns such as depletion and waste management. This leads to incorporate natural fibers into the matrix to form eco-friendly composite materials for possible usage in marine applications. Moreover, they offer high specific stiffness and low environment footprint. The aging mechanism of flax/PLA biocomposites was observed under natural seawater for the period of 2 years. This study elucidates that biocomposites suffer from relatively high moisture absorption, which is controlled by the vegetal fibers [42]. There is necessity to control aging of biocomposites in a seawater environment of both natural fiber and matrix. The extra coating layer of the similar biopolymer on biocomposite may enhance the reduction of weight gain by the interface of the fiber and matrix. The mechanical and thermal properties of the biocomposites after immersion show that the protective layers reduce hydrolysis of the matrix, retain the composite properties, and enhance their durability [43]. DuPontTM specially made marine composite with Kevlar, which is useful to provide an ideal balance of strength, stiffness, and lightweight properties for many marine applications. This enhances the higher speeds in patrol and service boats that can be achieved by increasing engine power. These composites made with Kevlar be lighter yet tougher, damage tolerant and perform better under hydrodynamic fatigue loading [44]. Davies [45] studied the environmental degradation of composites for marine structures and reported that the use of composites in highly loaded marine components, such as tidal turbine blades or composite propellers, is increasing and requires a detailed understanding of coupling between stress and seawater. A very few experimental data available rather than the theoretical framework, and the time being process for conducting couple of experiments and require specific test equipment. This is an area where further work is urgently required [45].
