Bamboo fiber reinforced polypropylene composites for transportation applications

The global truck/trailer transportation industry has experienced significant growth over the past few decades. This growth can be attributed to several factors, including increasing global trade and commerce, rising demand for goods and services, and improvements in transportation infrastructure and technology. While several materials can be used for truck/trailer decking applications, these materials must meet specific requirements, such as excellent fatigue, impact a corrosion resistance, high stiffness-to-weight ratio and high strength. With the projected growth in the global truck trailer market, developing advanced and high-performance materials for transportation applications is of great importance.

Apitong wood, also known as Keruing, is a tropical hardwood species that is commonly used in the transportation industry for truck and trailer decking applications. It is a strong, durable, and resilient wood species that is well-suited for heavy-duty use and can withstand the harsh conditions and extreme weather conditions that are often encountered in the transportation industry. However, due to habitat loss and excessive use, Apitong has been recently listed as an endangered species, necessitating an urgent need to develop alternative materials for trailer decking applications. Natural fiber composites have attracted growing research attention as promising alternatives. Compared with synthetic fibers, they are biodegradable, sustainable and environmentally benign materials with remarkable vibration dumping properties. In particular, bamboo fiber (BF) is commonly used to reinforce composites. Moreover, their exemplary attributes, such as lightweight, low density and higher tensile strength, make them potential candidates for replacing Apitong in trailer decking applications.

The properties of different BF composites, including sisal, coir and polypropylene (PP), have been extensively studied. However, BF composites used in most of these studies have been fabricated via hand lay-up processes and injection, extrusion and compression molding, with limited research on the application of overmolding process. Overmolding is a typical hybrid manufacturing technique currently used mostly in the aerospace and automotive industries. Its benefits include the ability to fabricate advanced lightweight and high-performance composite parts as well as reduce waste and energy consumption, all of which are vital in the fabrication of next-generation BF composite for transportation applications.

Herein, Dr. Sanjita Wasti, Dr. Surbhi Kore, Dr. Pritesh Yeole and led by Professor Uday Vaidya from the University of Tennessee in collaboration with Dr. Halil Tekinalp and Dr. Soydan Ozcan from Oak Ridge National Laboratory explored the development and properties of BF reinforced PP composites as a possible alternative to Apitong. The transport application of the resulting bamboo composites in trailer decking was also investigated. Their work is currently published in the research peer-reviewed journal, Frontiers in Materials.

In their approach, the PP-BF composites with different contents of BF (5, 10, 15 and 20 wt.%) were fabricated via extrusion-compression molding technique. Additionally, the trailer decking panels were formed by overmolding the bamboo strips with PP-BF. The properties of the overmolded trailer decking panels and extruded PP-BF were studied using morphological, thermal and mechanical characterization techniques. Additionally, besides testing the flexural loading and the nail pull-out strength of the basis panels, the feasibility as viable trailer decking material was also evaluated.

The research team carried out a detailed comparison of the nail pull-out strength of Apitong and bamboo composites. Results showed that the modulus and flexural strength of bamboo composites were 98% and 17% higher than that of Apitong, respectively. Consequently, the bamboo thermoplastic had a relatively lighter density (670 kg/m³) compared to 737 kg/m³ of Apitong. The PP-BF-panels also exhibited self-healing properties against the cracks and damages. When 20 wt.% BF was added, the tensile strength decreased by 8%, while the modulus increased by 85%. Furthermore, SEM images exhibited a poor fibre-matrix interface.

In summary, the authors investigated trailer-truck transportation applications of the bamboo fiber-reinforced PP composites. A trailer decking panel prototype was fabricated. Its practical performance was evaluated under aggressive loading conditions, and it exhibited minimal internal damage, excellent surface wear response and could withstand up to 400 fatigue cycles. In a statement to Advances in Engineering, Professor Uday Vaidya stated that the excellent performance of PP-BF-bamboo strips makes it a promising alternative to Apitong for trailer decking applications.