Investigation of optimal surface reatments for carbon/epoxy composite adhesive joitns

摘要

although an adhesive an adhesive joint can distribute the load over a larger area than a mechanical joint,requires no holes,addsvery little weight to the structure and has superior fatigue resistance,but it not only requires a careful surface prepration of the adherends but also is affected by service environments.In this paper,suitable conditions for surfacetreatments such as plasma surface treatment,mechanical abrasion,and sandblast treatmetn were ivnestigated to enhance the mechanical load capabilities of carbon/epoxy composite adhesive joints.A capacitively coupled radiofrequency plasma system wasused for the plasma surface treatment of carbon/epoxy compositesand suitable surface treatmetn conditions were experimentally investigated withrespect to gas flow rate,chamber pressure,power intensity,and surface treatment time by measuring the surface free energies of treated specimens.The optimalmechanicla abrasion conditions with sandpapers were investigated with respect to the mesh number of sandpaper,and optimal sandblast conditions were investigated with respect tosandblastpressure and particle size by observing geometric shape changes of adherendsduringsandblast process.also the failure modes of composite adhesive joints were investigated with respect to surface treatment.From the peel tests on plasma treatedcomposite adhesive joitns,it was foudn that all composite adhesive joints failed cohesively in the adhesive layer when the surface free energy was higher than about 40 mJ/m~2,because of high adhesion strength between teh plasma treatedsurface dn the adhesive.from teh peel tests on mechanically abraded composite adhesive joints,it was also found that the optimal surface roughness and adhesive thickness increased as the failure load increased.