Exploiting damage for inhibiting damage: A counterintuitive reasoning out of in-situ orthogonal cutting for brittle fiber composite

Abstract

The low-damage manufacturing of brittle fiber-reinforced composites has been facing significant challenges due to subsurface damage (SSD) caused by stochastic crack propagation. Traditionally, aggressive machining processes have been deliberately avoided during precision finishing of brittle fiber-reinforced composites to prevent SSD. Inspired by nature, we propose a counterintuitive concept (i.e., exploiting damage for inhibiting damage). To this end, in-situ observation experiments using optical microscopy and high-speed camera were developed to comparatively characterize subsurface fiber deflection, subsurface conditions at different time points and real-time cutting forces. Scanning electron microscopy was employed to observe the transformation of material removal modes with and without controlled damage layer (CDL), as well as the final SSD depth. The experiment results showed that the CDL significantly reduced fiber deformation, cutting force, and subsurface damage. Furthermore, based on the relationship between uncut chip thickness and CDL depth, two CDL scenarios of mechanism for SSD improvement were discussed. The fundamental mechanisms lie in a shielding effect that localizes stress concentration above the CDL. And a stress-mode transition that shifts tool-workpiece tensile and compressive stress status. Meanwhile, mesoscale numerical modeling was used to analyze stress concentration and tensile-compressive stress states, providing deeper insights into the influence of CDL, particularly the positive effect of the pinning phenomenon on damage inhibition. Based on experiment observation and mechanism understanding, the concept opens a counterintuitive yet effective avenue for precision manufacturing of brittle fiber-reinforced.