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.

This paper introduces a quadruped soft-amphibious robot using 4.0 mm diameter thin and soft McKibben actuator. The robot utilizes its leg and body bending mechanism to locomote. For each leg, three links of the actuators are arranged in parallel with fixed upper and bottom part. Then, four actuators are arranged in parallel and fixed with a thin plastic plate in between the actuators for the body motion. The elastic deformation of the plastic plate actuated by the actuators assist in the side-to-side motion of the robot mimicking the gait of the biological creature like lizard/salamander during walking motion. FEM simulation studies were performed in Marc Mentat® to evaluate the bending behaviors and validated with an experimental test. Walking experiment was tested on a flat surface and on sand using two different gaits of trot and crawl gait. On the other hand, swimming experiment was tested inside water using only crawl gait. Different input pressure and frequency were varied to study the walking behavior. The robot successfully walks on a flat and 10 o incline plane with a maximum speed of 0.056 m/s using trot gait and robust to move on sand and in water using the crawl gait at 0.041 m/s and 0.022 m/s, respectively.

Soft actuators are generally built to achieve extension, contraction, curling, or bending motions needed for robotic or medical applications. It is prepared with a cylindrical tube, braided with fibers that restrict the radial motion and produce the extension, contraction, or bending. The actuation is achieved through the input of compressed air with a different pressure. The stiffness of the materials controls the magnitude of the actuation. In the present study, Silastic-P1 silicone RTV and multi-wall carbon nanotubes (MWCNT) with reinforced silicone are considered for the evaluation. The dumbbell samples are prepared from both materials as per ASTM D412-06a (ISO 37) standard and their corresponding tensile strength, elongation at break, and tensile modulus are measured. The Ogden nonlinear material constants of respective materials are estimated and used further in the finite element analysis of extension, contraction, and bending soft actuators. It is observed that silicone RTV is better in high strain and fast response, whereas, silicone/MWCNT is better at achieving high actuation.

No abstract