2.2.2. Lapping Experiment Details

The surface roughness and the material removal rate (MRR) are the most relevant parameters to reflect the lapping machinability of materials. Thus, the MRR and surface roughness with abrasive paper lapping were studied in this work to analyze the influence of fiber types and mass fraction on the lapping machinability of fiber-reinforced PEEK.

All lapping experiments were conducted on an ultra-precision lapping machine (ZYP230, Shenyang Kejing Instrument Inc., Shenyang, China). The sample was a square block made by wire cutting with a size of 15 mm × 15 mm × 10 mm. The different mesh size of silicon carbide abrasive paper was applied in the lapping process to obtain the best surface roughness. During lapping, four samples for the same material were placed on a sample carrier in the once lapping process. A schematic diagram of the lapping experiment is shown in Figure 1.

**Figure 1.** The lapping experimental setup.

The lapping parameters for the PEEK machinability analysis are presented in Table 1. The material removal rate (MRR) was calculated by the change of sample thickness per unit time and the sample thickness change during lapping was measured by a laser measuring device (Technological Gocator 2520, LMI, Mississauga, ON, Canada). The surface roughness with abrasive papers of different particle sizes was measured after the lapping process by Talysurf Profiler (CLI2000, Taylor Hobson Ltd., Leicester, UK), and the surface morphology was observed by SEM (SU820, Hitachi, Tokyo, Japan).

**Table 1.** Lapping parameters for fiber-reinforced PEEK lapping machinability analysis.


## **3. Results**

*3.1. Material Properties of Fiber-Reinforced PEEK*
