Search

Over hundreds of millions of years, organisms have evolved architected structures via precise control over hierarchically assembled components, including the integration of dissimilar materials. One such example is found in the radula system of chitons, intertidal mollusks that feed on algae growing on the rock. Their radula consists of multiple rows of ultrahard teeth, each integrated with a foldable belt-like substrate via a stiff, yet flexible stylus, which is essential for efficient rasping during the feeding process. Here, we investigate the nano and micro-scale components and architectures as well as regional mechanical properties of the stylus, and their subsequent role during the rasping of Cryptochiton stelleri. Three important factors were determined to contribute to the regio-specific stiffness of the stylus: the presence of mineral components, highly oriented chitinous fibers, and a chemically cross-linked protein matrix. All these factors are varied throughout the stylus. There is a high mineral content on the trailing edge close to the tooth and a cross-linked matrix on the leading edge, both with orientational specific oriented chitin fibers that provide force transduction to the tooth. Conversely, there is a significant lack of mineral or cross-linked matrix in the proximal end as well as a low degree of fiber orientation, resulting in a flexible region that can accommodate torsion and flexure during rasping. Understanding the graded composite structure of the stylus and applying this unique design to various engineering fields such as soft robotics, biotechnology, and the medical industry, can inspire the production of high-performance materials. Graphical Abstract [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate in detail the usability of new cellulosic fibers extracted from the stem of the plant Strelitzia reginae, as a potential reinforcement for polymer composites. The morphological, physical, thermal, and mechanical properties of fibers were addressed for the first time in this paper. Both untreated and alkali-treated fibers were characterized, using scanning electron microscopy (SEM), Fourier-transform infrared, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), optical microscope, and X-ray diffraction (XRD) and applying tensile test for determining the mechanical behavior. For both fiber treated at one hour (T1H) and at four hours (T4H), the stem anatomy and fiber SEM micrographs showed a strong presence of fiber cells. Thermogravimetry and DSC showed that the fiber was thermally stable up to 233°C for untreated fiber, 254 and 240°C, respectively, In single-fiber tensile tests, it was observed that the fibers extracted from the stem of Strelitzia reginae were strong. The mean values of Young's modulus exhibited by untreated fibers and treated (T1H) and (T4H) are, respectively, 9.89 GPa, 12.08, and 18.39 GPa. Also mean values of tensile strength are 271.79, 306.23, and 421.39 MPa. The XRD reveals the presence of cellulose with a Crystallinity Index of 70% for raw fiber and 72% for the treated one. Fourier-transform infrared analysis well demonstrated the effect of chemical treatment. It can be concluded from the results of all above experiments that the Strelitzia reginae fibers (SR) could serve as a possible reinforcement in composite materials. [ABSTRACT FROM AUTHOR]

This study deal with the development and investigation of a novel hybrid nano-shell plant fiber biocomposite. Nano-calcium carbonate CaCO3 ranging from 1 to 5 wt% and 20 wt% banana fiber-filled hybrid biocomposite were prepared using a hand lay-up process followed by applying load on a closed mold. Nano-CaCO3 of near-uniform size and shape was synthesized from Achatina Fulica through a mechanochemical technique. The effect loading fiber of uniform 30 mm size on the mechanical, physical, thermal properties of greenpoxy composite was investigated. The influence of nano-CaCO3 loading (1 to 5 wt%) on banana fiber-filled greenpoxy composite, dynamic mechanical properties, tensile, flexural, impact strength was further investigated. The result showed that the loading of banana fiber improved mechanical properties and negatively affected temperature dependence storage modulus, loss modulus, and tan δ. Better load carrying and stress distribution capacity of the fiber within the biocomposites can be attributed to the high strength and stiffness observed for these series. The poor thermal properties of banana fiber can be ascribed to a decrease in the temperature dependence properties. The loading of nano-CaCO3 improved most of the banana-filled greenpoxy biocomposite, and hybrid composite with 2 wt% nano-CaCO3 offered superior properties. Uniform dispersion, excellent matrix/nano-CaCO3/banana fiber adhesion provided a strong structure, resulting in improved mechanical and temperature-dependant properties. [ABSTRACT FROM AUTHOR]

This paper reports the effect of lignocellulosic flour and talc powder on the thermal degradation behavior of poly (lactic acid) (PLA) by thermogravimetric analysis (TGA). Lignocellulosic flour was obtained by grinding Opuntia Ficus Indica cladodes. PLA/talc/ Opuntia Ficus Indica flour (OFI-F) biocomposites were prepared by melt processing and characterized using Wide-angle X-ray scattering (WAXS) and Scanning Electron Microscope (SEM). The thermal degradation of neat PLA and its biocomposites can be identified quantitatively by solid-state kinetics models. Thermal degradation results on biocomposites compared to neat PLA show that talc particles at 10 wt % into the PLA matrix have a minor impact on the thermal stability of biocomposites. Loading OFI-F and Talc/OFI-F mixture into the PLA matrix results in a decrease in the maximum degradation temperature, which means that the biocomposites have lower thermal stability. The activation energies (Ea) calculated by the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) model-free approaches and by model-fitting (Kissinger method and Coats-Redfern method) are in good agreement with one another. In addition, in this work, the degradation mechanism of biocomposites is proposed using Coats-Redfern and Criado methods. [ABSTRACT FROM AUTHOR]