Assessment of the reduction of fiber-matrix debonding in fiber-reinforced composite edge tool machining using water jets

Machining workpieces made of fiber-reinforced composites (FRC) with edge tools have a large range of applications. However, one of the drawbacks is the resulting fiber-matrix debonding in a thin layer under the machined surface. This can decrease the operational properties of the machined composite parts. A number of techniques are available to minimize machining defects in FRCs, with varying degrees of effectiveness. Fiber-matrix debonding results from the fibers having higher strength than the matrix. Consequently, during machining, the fibers bend to a greater angle compared to the matrix areas. To minimize this bending and debonding, we propose fiber counter-deflection in front of the cutting zone through water-jet pressure on the work surface. We verified this proposal using two methods: a smoothed particle hydrodynamics (SPH) simulation of the cutting process and full-scale experiments with a robotized water-jet cutting device and a special edge cutting tool. Both the calculations and the experiments generally confirmed the hypothesis of minimizing fiber debonding. Planing a FRC workpiece using water-jet pressure on the work surface provided a decrease in the length of fiber debonding by only 13% on average. This decrease is not high, but the simulations and experiments are only the initial investigations into improving the surface quality using this approach. At present, quality improvement of FRC workpiece machining with edge tools can be achieved with water-jet pressure using additional water-jet nozzles in these tools. Therefore, this paper presents the results of theoretical and experimental studies of a new technique based on the use of water jet to reduce fiber-matrix debonding.