A Review on Thermoplastic or Thermosetting Polymeric Matrices Used in Polymeric Composites Manufactured with Banana Fibers from the Pseudostem

Recent manufacturing advancements have led to the fabrication of polymeric composites (PC) reinforced with fibers. However, to reduce the impact on the environment, efforts have been made to replace synthetic fibers (SF) by natural fibers (NF) in many applications. NF, e.g., as banana fibers (BF) possess higher cellulose content, a higher degree of polymerization of cellulose, and a lower microfibrillar angle (MFA), which are crucial factors for the mechanical properties (MP), namely tensile modulus (TM) and tensile strength (TS), and many other properties that make them suitable for the reinforcement of PC. This review paper presents an attempt to highlight some recent findings on the MP of PC reinforced with unmodified or modified BF (UBF, MBF), which were incorporated into unmodified or modified (synthetic (SPM) or a bio (BPM)) polymeric matrices (UPM, MPM). The experimental results from previous studies are presented in terms of the variation in the percentage of the MP and show that BF can improve the MP of PC. The results of such studies suggest the possibility to extend the application of PC reinforced with BF (PCBF) in a wide range, namely from automotive to biomedical fields. The meanings of all the acronyms are listed in the abbreviations section.

The combined effects of initial microfibrillar angle and moisture contents on the tensile mechanical properties and angle alteration of wood foils during tension

The combined effects of initial microfibril angle (MFA) and moisture content (MC) on the longitudinal tensile properties of Masson pine (Pinus massoniana Lamb.) wood foils has been investigated. Synchrotron X-ray diffraction (XRDsyn) combined with a custom-built microtensile device was applied for in situ monitoring of the MFA alterations in the foils under different initial MFAs and MCs conditions. The results demonstrate that the tensile properties are highly negatively correlated to both MFA and MC. Furthermore, the tensile modulus is more sensitive to MC change than tensile strength. At a higher MFA, the sensitivity of the two mechanical indicators to MC alteration is enhanced.

Variation of mechanical properties of single bamboo fibers (Dendrocalamus latiflorus Munro) with respect to age and location in culms

There is a growing need to characterize the mechanical properties of single bamboo fibers with their high potential in commercial applications. In this paper, an improved microtensile technique has been applied to measure the tensile strength of fibers isolated from Ma bamboo (Dendrocalamus latiflorus Munro) as an important commercial bamboo species in China. The property variation with respect to the age and locations within a culm was in focus. Ma bamboo fibers had superior stiffness and strength data compared with those of softwood fibers. Four-year-old Ma bamboo fibers are stiffer and stronger than 1-year-old fibers. Their in-trunk variation is rather small both in radial and longitudinal directions. This is due to the relatively constant microfibrillar angle in bamboo culms. Accordingly, the large variations in the bulk mechanical properties of bamboo are mainly attributable to fiber distribution density in the culm rather than the fiber itself.

Mechanical characterization of single bamboo fibers with nanoindentation and microtensile technique

More mechanical information on fibers is needed for better understanding of the complex mechanical behavior of bamboo as well as optimizing design of bamboo fiber based composites. In this paper, in situ imaging nanoindentation and an improved microtensile technique were jointly used to characterize the longitudinal mechanical behavior of fibers of Moso bamboo (Phyllostachys pubescens Mazei ex H. de Lebaie) aged between 0.5 and 4 years. These methods show that 0.5-year-old fibers have similar mechanical performances to their older counterparts. The average longitudinal tensile modulus and tensile strength of Moso bamboo fibers ranges from 32 to 34.6 GPa and 1.43 to 1.69 GPa, respectively, significantly higher than nearly all the published data for wood fibers. This finding could be attributed to the microstructural characteristics of the small microfibrillar angle and scarcity of pits in bamboo fibers. Furthermore, our results directly support the assumption that the widely used Oliver-Pharr analysis method in nanoindentation test significantly underestimates the longitudinal elastic modulus of anisotropic plant cell wall.

Characterisation of a Soft Rot-Like Decay Pattern Caused by Coniophora puteana (Schum.) Karst. in Sapelli Wood (Entandrophragma cylindricum Sprague)

Summary The decay patterns of brown and soft rot fungi in Sapelli wood (Entandrophragma cylindricum Sprague), with respect to natural durability, were examined by light and transmission electron microscopy as well as UV spectroscopy. Analyses revealed that the typical brown rot fungus Coniophora puteana can cause a soft rot-like decay in the sapwood of Sapelli at high moisture contents of approx. 100%. In accordance with the decay pattern of the typical soft rot fungus Chaetomium globosum, the hyphae of C. puteana penetrated the S2 wall of fibres and formed characteristic rhomboidal cavities orientated parallel to the microfibrillar angle. However, these cavities were larger in diameter (3.9 μm ± 0.9) than those formed by C. globosum (2.1 μm ± 0.5) and with a distinct interspace between the hyphae and surrounding walls. Hyphae of C. globosum were directly attached to the undecayed secondary wall. No lignin degradation for both fungi in close vicinity to the cavities was observed, as evidenced by UV spectroscopy. The inclusion of microscopy for definitive decay type identification is recommended.

Elasticity and microfibrillar angle in the wood of Sitka spruce

The initial value of Young’s modulus, E , has been measured for small specimens of Sitka spruce wood taken from the annual rings of two disks and has been found in both cases to increase from pith to bark. The decrease from pith to bark in the helical angle θ of the cellulose microfibrils in the walls of the tracheids averaged over an annual ring has been determined from matched specimens. E has been found to vary regularly with θ . Two mathematical models of the cell involved have been developed and the experimental findings applied to the relations derived between E and θ . The first model was that of a number of helical springs free to slip, twist and bend and gave a relationship between the helical angle and the reciprocal of Young’s modulus as proportional to tan 2 θ . The second model, that of an anisotropic homogeneous cell wall, gave 1/ E as being proportional to a quadratic function in sin 2 θ . Relative shear in the cell wall has been predicted from this latter model. The tan 2 θ relation is found to hold provided θ is less than about 40°. The sin 2 θ relation holds, on the other hand, over the full range of θ observed. Some implications of these relations are discussed.