## 4 Mechanical Properties of Polymeric Composites Reinforced with Banana Fibers
Therefore, good interfacial adhesion between the PM and BF is essential to improve the mechanical strength in the PCBF. The incorporation of BF at variable FL from 10 to 40 wt % resulted in a consistent increase in the modulus of PCBF. However, higher FL also results in the formation of voids in the PCBF because of BF/BF agglomeration due to H-bonding between the BF leading to non-uniform distribution of BF within PM, which results in the deterioration in MP. The IS of a PCBF depends on many factors, such as the toughness properties of the reinforcement, the nature of the interfacial region, and frictional work involved in pulling out of the BF from the PM. The nature of the IR is of extreme importance in determining the toughness of the PCBF. If the interfacial bonding of the PCBF is weak, the crack will be propagated along the BF/PM, causing debonding. As a result of debonding, new surfaces will be produced, which leads to a significant increase in the energy-absorbing capacity of the PCBF. Therefore, it can be expected that the IS of the untreated polymeric composites reinforced with untreated banana fibers (UPCUBF) would be higher when compared to MPCMBF. However, in Appendix F (Table A6), the variation in percentage (average values) of the IS reached a value of 1105 for PCWBF with different BF FL (5, 10, 15, and 20 vol %) + SCT (1%, 3%, and 5% of NaOH and C\({}_{3}\)H\({}_{4}\)O\({}_{2}\)). Moisture Absorption Studies of Polymeric Composites Reinforced with Banana Fibers-Some Obtained Results  
As mentioned before, BF has a hydrophilic nature and high cellulose content and also has the presence of lignin and hemicellulose components that can absorb the water molecule and swell. For this reason, BF can present some incompatibility within the PM which increased the microvoids, thus resulting in microcracks on the IR of the PCBF, which enhances the moisture absorption tendency. However, the hydrophilicity of BF can be reduced with different SCT. Appendix G (Table A7) summarizes the moisture absorption tendency of PC reinforced with UBF or with MBF from selected authors in different situations. From Appendix G (Table A7), some important conclusions can be drawn. The variation in moisture absorption tendency is positive in all cases. However, the highest variation in moisture absorption tendency was found for PCWUBF (20 vol % of UBF into a polyester PM) in comparison with the pristine PC, which reached a moisture absorption tendency of +2431(%) [137] for a saturation time of 143 h. The authors decreased this moisture absorption tendency with SCT of BF. The lowest mean values in moisture absorption tendency were found for PC with UPC (PP matrix; +1.35(%) of MAT), and MPC (with MA; +0.30(%) of MAT) reinforced with UBF (20 mm in length) at a FL of 10 vol % in comparison with the pristine PC. MAT decreased with the addition of PP_MA in comparison with the PC without MA. The MAT for the PP + PP_MA + UBF mixture was the lowest. The authors justified this result with the presence of hydroxyl groups on the hydrophilic nature of the BF and their interaction with the anhydride groups of the treated PM (PP_MA). In this case, the sequence of the mixture also influenced the MAT results. In another study, the authors decreased the moisture absorption tendency with the addition of MA into the PP in comparison with the PC without MA [100]. This was achieved due to the replacement of hydroxyl groups with hydrophobic ester groups by SCT treatments and by the incorporation of MA into the PM, which generates a chemical linkage between BF and PM and which reduces the microvoids' formation [37; 100]. On the other hand, the presence of BF reduces the hydrophilicity of the starch-based PC, because starch is more hydrophilic than cellulose [123]. Concluding, in all cases, the poor wettability and adhesion into the IR was attributed to the hydrophilic nature of BF, as expected. Section 2.3 of this paper focused on the direct and indirect surface treatments on the natural fibers and their influence on MAT.