AWJ machinability performance of CS/UPR composites with the effect of chemical treatment

This work focuses on the effect of chemical treatment of coconut sheath/unsaturated polyester (CS/UPR) composite on the performance of abrasive waterjet machining (AWJM). Two different chemical treatments, namely alkali (NaOH) and trichlorovinylsilane, were imposed on the CS fiber. Further, the induced compressive strength arising as a result of AWJM was studied along the radial and depth directions of the composite. Experimental results revealed significantly lower induced stress at all points compared to the ultimate stress of CS/UPR composites except the free-edge loading condition. The chemically treated composites also exhibited inconsistent results in the machining characteristics such as kerf taper angle (T-a) and surface roughness (R-a) under varying cutting conditions. However, no direct correlation was seen between interfacial adhesion and T-a and R-a of the cutting zone. The maximum decrease of 12% of T-a and 22% of R-a was found for silane-treated composites compared to the untreated ones. In addition, the composite failure mechanisms such as fiber pullout, fiber breakage, interfacial debonding, matrix failure, and voids were identified in the cutting surfaces through scanning electron microscopy analysis.