Towards intelligent CFRP composite machining: Surface analysis methods and statistical data analysis of machined fibre laminate surfaces

Abstract

Many carbon fibre reinforced polymer composite parts need to be edged trimmed before use to ensure both geometry and mechanical performance of the part edge matches the design intent. Measurement and control of machining induced surface damage of composite material is key to ensuring the part retains its strength and fatigue properties. Typically, the overall surface roughness of the machined face is taken to be an indicator of the amount of damage to the surface, and it is important that the measurement and prediction of surface roughness is completed reliably. It is known that the surface damage is heavily dependent on the fibre orientation of the composite and cutting tool edge condition. This research has developed a new ply-by-ply surface roughness measurement methods using optical focus variation surface analysis and image segmentation for calculating areal surface roughness parameters of a machined carbon fibre composite laminate. Machining experiments have been completed using a polycrystalline diamond edge trimming tool at increasing levels of cutting edge radius. Optical surface measurement and µ-CT scanning have been used to assess machining induced surface and sub-surface defects on individual fibre orientations. Statistical analysis has been used to assess the significance of machining parameters on Sa (arithmetic mean height of area) and Sv (areal magnitude of maximum valley depth) areal roughness parameters, on both overall roughness and ply-by-ply fibre orientations. Empirical models have been developed to predict surface roughness parameters using statistical methods. It has been shown that cutting edge degradation, fibre orientation and feed rate will significantly affect the cutting mechanism, machining induced surface defects and surface roughness parameters.

The effect of particle reinforcements on chip formation and machining induced damage of modified epoxy carbon fibre reinforced polymers (CFRPs)

“…These results are linked with the high fracture toughness of the rubber modified epoxy, limiting the crack growth along the matrix in 135° fibre orientation, thus decreasing the amount of pull-out material and subsurface damage. As shown in Figure 10 and previously in the literature [12], [13], [40], fibre orientation has a strong influence on the generated surface topography after machining. DGEBA samples represent the reference material in Figure 11.…”

“…The volume of indentations (craters) observed on the 135° plies was calculated using the Dragonfly CT segmentation software (Figure 7b)). These have previously reported during machining of CFRPs [12], [13] and it was found that they adversely affected the mechanical properties of the samples namely flexural and compressive strength [14], [41], [42]. All the machined surfaces showed significant matrix smearing across all fibre orientations.…”

A seven-question based critical thinking framework for cultivating innovation talents in engineering research and its implementation perspectives

“…4 In the current dynamic era with big challenges, disruptions and uncertainties, new requirements and technologies are emerging at an unprecedented speed. 5,6 In engineering area, new manufacturing equipment and technologies, measurement methods and technologies as well as related upstream technologies are emerging day by day, [7][8][9] only the researchers with innovation capability can keep up with the development pace of new technologies. The lack of originality will lead to weak competitiveness for a person, a company as well as for a country.…”

A Novel Finite Element Method Approach in the Modelling of Edge Trimming of CFRP Laminates

“…The orientation of the cracks plays a fundamental role in the appearance of defects in the mechanical surface, such as surface roughness or sub-surface damage. A clear increase in these variables is observed in fibre orientations greater than 90 • due to the fact that the great bending effect causes the fibre breakage to occur in a very irregular way below the cutting surface as well as a significant increase in the fibre matrix debonding extension into the sub-surface damage [40,41].…”