# A Novel Finite Element Method Approach in the Modelling of Edge Trimming of CFRP Laminates
## 2 Experimental Set-Up  
The milling process differs from orthogonal cutting in that there is a rotating tool with multiple cutting edges and intermittent contact of each cutting edge with the workpiece. Additionally, there is also a constantly changing thickness in the size of the removed chip as the tool is fed into the workpiece. A conventional edge trimming approach was applied in this experiment, which means that the size of the chip will increase as the tool increases engagement with the workpiece. In a composite edge trimming process, the milling kinematics mean that there will be a new fragmented chip generated for every new pass of a cutting tooth. The effect of fibre orientation also plays a role, which will change in relative orientation to the cutting edge with the rotation of the milling tool, as shown in Figure 1.  
The edge trimming machining experiments were completed on a uni-directional laminate with two different fibre orientations: \(-45^{\circ}\) and \(90^{\circ}\) fibre orientations. The carbon fibre laminates were manufactured by pre-prep hand layup and were cured in an autoclave. A fibre type T700G and an epoxy matrix named Hexply M21 were employed. A five axis Computer Numerical Control (CNC) machine tool, Cincinnati FTV5-2500, Cincinnati machines, Ohio (EEUU), was used to machine the carbon fibre material, see Figure 2.  
A polycrystalline diamond (PCD) cutting tool was selected. Unidirectional CFRP laminates of 36 plies were vacuum bagged to be cured in an autoclave. The curing cycle selected is specified in the below list.  
1. Apply full vacuum (1 bar).
2. Apply 7 bar gauge autoclave pressure.
3. Reduce vacuum to a safety value of \(-0.2\) bar when the autoclave pressure reaches 1 bar gauge
4. Set heat-up rate from room temperature to 180 \({}^{\circ}\)C \(\pm\) 5 \({}^{\circ}\)C (356 \({}^{\circ}\)F \(\pm\) 9 \({}^{\circ}\)F) to achieve an actual component heat-up rate between 1-2 \({}^{\circ}\)C/min (2-4 \({}^{\circ}\)F/min).
5. Hold at 180 \({}^{\circ}\)C \(\pm\) 5 \({}^{\circ}\)C (356 \({}^{\circ}\)F \(\pm\) 9 \({}^{\circ}\)F) for 120 min \(\pm\) 5 min.
6. Cool component at an actual cooldown rate of 2-5 \({}^{\circ}\)C/min (4-9 \({}^{\circ}\)F/min).
7. Vent autoclave pressure when the component reaches 60 \({}^{\circ}\)C (140 \({}^{\circ}\)F) or below.  
Figure 1: Relative fibre orientation change in edge trimming—orange stripes = fibre, green stripes = matrix.  
Figure 2: Five axis CNC machine tool, Cincinnati FTV5-2500.  
This laminate was cut into samples (at the required fibre orientations), which had length, width and thickness--160 mm, 63 mm and 6 mm, respectively. These samples were fixed using a clamping system as shown in Figure 3 and attached to the CNC machine tool. The cutting forces were recorded during the experiment by using a Kistler dynamometer, which was attached to the base of the CNC machine as shown in Figure 3. The effect of cutting tool wear on the machining forces was recorded by measuring the \(F_{X}\) (feed force) and \(F_{Y}\) (thrust force), depicted in Figure 3.  
The mean cutting forces were calculated and compared with numerical models, which were then used to validate FE cutting simulations. The PCD cutting tool had a 0 helix angle and 10 mm diameter, as shown in Figure 4. Two cutting tools were used in two different conditions in new and worn condition, with a 3 \(\upmu\)m and 10 \(\upmu\)m edge radius, respectively. The tool tooth had a clearance angle of 22.4\({}^{\circ}\), and a rake angle of 29.8\({}^{\circ}\) with a negative 1 mm offset from the centre line. Each test was repeated 2 times with each cutting tool condition. The samples were cut with a full thickness axial depth of cut (\(ap\)) of 10 mm and a radial depth of cut of 2 mm. A spindle speed of 6000 rpm and 1200 mm/min feed rate was applied using the three flute PCD cutting tool.