Experimental investigation of the influence of sandblasting parameters on surface roughness, porosity and coating performance of CFRP laminates

Surface preparation plays a fundamental role in determining the quality and performance of coated carbon fibre reinforced polymer (CFRP) components. Among the available techniques, sandblasting is widely adopted to improve coating adhesion by increasing surface roughness. However, excessively aggressive treatments may generate surface defects, particularly porosity, which can compromise the aesthetic quality of the painted component. The objective of this thesis was to investigate the influence of the main sandblasting parameters on surface roughness, surface porosity and coating performance of CFRP laminates in order to identify process conditions capable of balancing functional and aesthetic requirements. An experimental campaign based on a full factorial Design of Experiments (DOE) was carried out by varying pressure, stand-off distance, exposure time and abrasive quality. Surface characterization included roughness measurements (Ra and Rq), image analysis of surface porosity, coating thickness evaluation and cross-cut adhesion testing according to ISO 2409. The results showed that pressure was the most influential parameter governing surface porosity generation, while the comparison between fresh and aged abrasive media highlighted significant differences in the resulting surface morphology. A trade-off between roughness and porosity was observed, indicating that increasing the aggressiveness of the treatment does not necessarily produce a proportional increase in surface defects. Furthermore, the applied coating significantly reduced the residual surface irregularities, whereas all tested specimens exhibited excellent adhesion performance. Overall, the study provides practical guidelines for the optimization of industrial sandblasting processes and contributes to a better understanding of the relationship between process parameters, surface morphology and coating performance in CFRP components.