The Preparation Of The Protective Coating On Resin Matrix Composite And The Study On The Fractal Dimension

By now, tensile strength test is the main idea to test the bonding strengthbetween the coatings and substrate. However, as the improvement of the coatingmaterials, coating technologies and plasma spraying technology, the adhesionstrength increased a lot. Especially, when the coatings and substrates are bothalloys, the adhesion strength is higher than that of the binder material used in thetensile strength test, which make it hard to examine the adhesion strength bytraditional tensile test. Therefore, a new test method is needed. Based on recentresearch, the nonlinearity, irregularity and self-similarity of the interface betweenthe ceramic coatings and substrate have effects on the adhesion strength.Therefore, the fractal theory can be used to measure the bonding strength. Basedon the nonlinearity, irregularity and self-similarity of the interface between theceramic coatings and polymer substrate, this study focused on the relationshipbetween the fractal dimension and adhesion strength of the coatings, whichsimplified the adhesion strength test and optimized the parameters of the process.This work also studied on the effects of the thickness of bond coatings and topcoatings together with spray parameters on the adhesion strength, and optimizedthe parameters.The results reflect that the fractal dimensions can be used to measuring theadhesion strength. The more complex of the morphologies of interface is, thehigher value of the fractal dimensions are, and the higher bonding strength is.And when the thickness of the top coatings is still, the thicker the bondingcoatings are, the poorer properties of the coatings are. Considering the protectivefunction of the bond coatings, the best thickness of bond coating is100μm. Whenthe thickness of bond coating is still, the properties of the top coating increaseswith thickness, and polishing process will be taken after plasma spray process.Therefore, the best thickness of the top coating is400μm. By orthogonal experiments, we have ordered the level of influences of the three mainparameters of plasma spraying on the adhesion strength and obtained theoptimized parameters: the order from high to low: spray current, spray voltage,spray distance; optimized parameters:300A,60V,180mm. This method usingfractal dimensions can reduce test work, increase efficiency and reduce cost.