Abstract
The machining of composite materials is difficult because of their non-homogenous structure and their constituents commonly possess a high resistance to cutting. Abrasive waterjet machining (AWJM) is more attractive for composite substrates than conventional machining techniques because of its ability to rapidly machine a wide variety of materials with low reactionary forces on the workpiece, and without creating a heat-affected zone. However, AWJM is prone to producing variable surface roughness and delamination. This dissertation aimed to model these surface roughness and delamination mechanisms. The thesis presents 2D and 3D roughness models capable of predicting the surface roughness during abrasive waterjet (AWJ) trimming of composite substrates. The models were able to predict the measured surface roughness with an average error of 10% and 16%, for the 2D and 3D models, respectively. The thesis also presents experimental and numerical results characterizing the delamination when AWJ piercing and cutting a carbon-fiber/epoxy laminate. Fluid-structure interaction (FSI) models created to simulate the piercing process showed that interlaminar delamination was due to the hydraulic shock (‘water hammer’) associated with liquid jet impact. As expected, increased pressure and nozzle size resulted in ply debonding, and was experimentally verified using 3D x-ray micro-tomography. The composite anisotropy was found to produce an asymmetric shock loading along the liquid-solid interface, which contributed to the asymmetric delamination. The FSI model showed that delamination when cutting carbon-fiber/epoxy depended primarily on the normal interlaminar stress, with relatively large damage zones occurring ahead of the cutting front. This trend was also observed in x-ray micro-tomographs of an AWJ cut. The amount of delamination across different process parameters was also measured using a moisture uptake methodology, and showed that increase traverse speed, increased nozzle size, and decreased abrasive flow rate, increased delamination. Prediction and characterization of surface roughness and delamination when AWJM will allow further improvement of cut-surface finish and structural integrity of composite materials, respectively
Highlights
This is a manuscript-based dissertation is based on the following publications: 1) J
The results suggest that the primary mode of material removal of the fibers was fracturing by either shear fracture or micro-bending near the jet exit; while micro-cutting of the fibers and matrix were predominant in the smooth cutting region (SCR)
Saleem et al [167], in a comparison of Abrasive waterjet machining (AWJM) hole trepanning to conventional hole drilling in composite materials, showed that AWJM led to better fatigue strength characteristics
Summary
This is a manuscript-based dissertation is based on the following publications: 1) J. AWJM is ideal for processing composite materials containing hard reinforcing particles or fibers because it produces no heat affected zone, minimal tool wear, and results in negligible residual stresses and workpiece reaction forces [3]. AWJM is ideal for cutting and drilling composite materials containing hard reinforcing particles or fibers because it produces no heat affected zone, minimal tool wear, and results in negligible residual stresses and workpiece reaction forces [3]. Ho-Cheng [44] described the delamination during drilling by waterjet piercing using a fracture mechanics approach with plate theory He proposed a model that relates delamination damage to waterjet pressure and laminate properties. Abrasive waterjet machining (AWJM) uses the mechanism of single particle impact erosion to rapidly remove material from a target substrate by accelerating particles using an ultra-high pressure (UHP) water jet. It is of great interest to develop principles, models, and practices to reduce damage and increase cut quality when AWJM of composite materials
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
