## 4 Mechanical Properties of Polymeric Composites Reinforced with Banana Fibers  
This section presents and compares the highest and lowest obtained results from selected authors with respect to some important MP of PC reinforced with UBF or MBF, namely tensile properties (TP), flexural properties (FP), and impact properties (IP). MP are important to know in PC to check their capability to withstand load and to estimate their lifetime [1]. TP, namely TM-Young's Modulus or Modulus of Elasticity (ME) and TS are usually measured from the stress-strain curve or force-displacement curve from tensile tests. The TM is measured at the elastic stage and represents the stiffness of the material. On the other hand, the ability of composite material to resist breaking under tensile load is the TS, which is the maximum value recorded in the stress-strain curve in the plastic regime [90]. Both these parameters characterize the rigidity of the PC [175; 176] and can be determined following ASTM standard test procedure D638 [177], which specifies dog-bone tensile test samples and is recommended for randomly oriented, discontinuous, moldable composites with TM less than 20.7 GPa (\(\approx\)3 MSI). For highly oriented and for high TM fiber-reinforced PC, it is recommended that the determination of TP follows the ASTM D3039 [175; 176; 178]. For the PC laminates case, it is recommended that the determination of TP follow the ASTM D882 [179]. For the determination of the TP of thermosetting reinforced plastics using test specimens of uniform nominal width, it is recommended to follow the ASTM D5083 standard [123]. Figure 2: Scheme with the principal steps for polymeric composites reinforced with natural fibers, manufacturing with or without surface chemical treatment of the natural fibers, and for treated or untreated polymeric matrices. FP, namely FM and FS, also known as the bending modulus and bending strength, respectively, are the stiffness and the ability to resist deformation under flexural loading, respectively. The FP are measured from static flexural tests usually carried out under a three-point bend configuration and performed according to ASTM D790 [180]. For the case of PC laminates, it is recommended that the determination of FP should follow the ASTM D1037 [181]. The IP of PC, namely the impact strength (IS), can be measured as a function of the impact energy (or the energy absorbed before fracture) divided by the notched cross-sectional area. The energy needed to break the PC can be used to measure the toughness of the PC and the yield strength. The effect of strain rate on fracture and ductility of the PC can be analyzed by using an Izod impact machine and following ASTM standard test procedure D256 [182]. After mechanical tests, Scanning Electron Microscope (SEM) or by Field Emission Scanning Electron Microscope (FESEM) can be performed on the fractured surface (FSF) of the specimens to understand the failure mechanisms. SEM studies can also be carried out on the tensile FSF of the specimens to understand the effect of different modification techniques on the fiber/matrix interfacial bonding and also to observe the morphology of the FSF on the PC (with or without unmodified or modified BF (UBF or MBF) into UPMs or MPMs) at the location near the crack tip and to assess the different modes of failure. It is important to mention that the PC needs to be conditioned (before mechanical testing), according to ASTM E41-92 [183]. In Appendices A and B (Tables A1 and A2), more information about the used methods for the extraction and preparation of BF related PC are presented. In Appendices C-F (Tables A3-A6), more information can be found about the variations in percentage (average values) of the TM, TS, FM, FS, and IS in the obtained results from selected authors, which investigated PC manufactured with BF randomly oriented (RO), as a function of the fiber loading (FL) at a fixed FL and into plasticized SM for specific banana fiber length (BFLg).