Investigation on the influence of humidity on the topography of surfaces of polymeric class a carbon fiber reinforced plastics
The origin of fiber print-through is commonly based on the influence of temperature during cure and post cure thermal treatments on polymeric matrix systems due to chemical and thermal shrinkage. Furthermore, it is proven that especially polymeric matrices are hygroscopic and therefore, have a disposition to soak up water in surroundings with a high level of humidity. Currently, to characterize influences like these on coated surfaces of carbon fiber reinforced plastics short and long wave values are applied which are actually developed to describe waviness of coating film structures of conventional materials like aluminum or steel. A fitted value regarding the phenomenon of fiber print-through is missing today to consider various influences on the surface topography. This investigation delivers a novel approach with a specific value to determine averaged altitudes caused by fiber print-through. For this purpose, the used confocal chromatic sensor by Fries Research and Technologies creates 3D images of surface topography and fiber print-through. This elaboration allows to correlate the change of mass of carbon fiber reinforced plastics due to thermal and hygrothermal post curing treatments with the characteristic of fiber print-through. Mass increase of 0.25% due to hygrothermal influence leads to a rise of print-through effect of about 210% and a decrease of mass of 0.5% due to thermal influence rises the characteristic of print through of about 75%.