Core Surface Finish 1

[CSrac]

As an N/C programmer, part of my job is to 5 axis program core details (non-metalic) for aircraft bond assemblies. We use several special cutters and some leave a rough finish which we currently remove with finish passes and sanding. What effect would a fuzzy core finish have on bond strength? We are now designing some pull and NDI test to compare, but I wondered if anyone else has an Idea what finish is necessary. Our spec is very general and only states " Machined fiber fuzz shall not be longer than .10 inches."

 

[Compositepro]

Generally the bond to the face sheet will be stronger with fuzzy core finish. But there can be other effects that may or may not be desireable. With vacuum bag cure there is often limited airflow from cell to cell due to pinch-off that occurs between the facesheet and cell walls. This pinch-off is usually good for surface finish because it prevents the cells from being evacuated which results in foaming of the adhesive or matrix resin in the facesheet. Fuzzy edges interfere with pinch-off.