Investigation on scratching force and material removal mechanism in scratching of fiber-reinforced resin matrix composites considering the effect of temperature

Fiber-reinforced resin matrix composites (FRC) are extensively utilized in aerospace due to commendable mechanical properties. However, during the machining process, FRCs are vulnerable to the effects of cutting heat, resulting in a reduction of their mechanical properties. As a result, the quality and precision of molded parts may suffer. Therefore, to examine the removal mechanism and damage forms of FRC under varying temperatures, this study utilizes QFRP (Quartz fiber reinforced polyimide resin matrix composites) as a prime example. Scratch tests on QFRP employ identical scratching parameters at different heating temperatures. The results are analyzed, including scratch force characteristics, cross-section profile characteristics, surface damage, and material removal mechanism. The results show that, firstly, with the increasing heating temperature, the scratch force fluctuates in a small range and then decreases significantly. Compared with 25°C, scratch force Fy and Fz amplitude decreases by 36.8% and 44.6%, respectively, when the heating temperature is 425°C. Secondly, due to the increase in temperature, the mechanical properties of the matrix decreased, increasing the scratch damage width with the increase in temperature. Finally, combined with the scratch SEM photographs, this study indicated that when the temperature was much below the matrix’s Tg, the polyimide matrix and quartz fiber were removed by the indenter by shear fracture. In contrast, when the temperature was close to or exceeded the matrix’s Tg, the matrix showed enhanced plasticity and mobility, resulting in the matrix undergoing significant plastic deformation, and the indenter removed the quartz fiber by bending fracture.