Coating Composites Mechanics Properties Research And Interface Strength Finite Element Analysis

When the original material is coated with a new material or composite materials, the material properties can be improved greatly, even the material can get new properties. Functional performance and life of the substrate materials can be improved by coating. As nano-materials have many properties in mechanics, electrics, acoustics, optics, calorifics, magnetics and so on, the emergence of nano-materials brings unprecedented opportunity to the coating technology development. It makes the functional properties of composite coatings improved significantly. With development of the coating technology, the reliability and use life of coatings become more and more important. The interfacial adhesion strength between the coating and the substrate largely determines the reliability and service life of the coating. It is the basic condition of coating function. And it is one of the most concerned issues in the coating manufacturing process. Either the coatings are used for electronic circuit, decorating and protecting or the wear resistant coatings are used in industry, the strong enough interfacial adhesion strength is the main factor of the durable coatings. The interface damage always leads to the whole coating system damage. Scratch test is the mainly used method to measure the interface adhesion strength. The stress distribution in the scratch test of the coating/substrate system is one of the most important parameters which control the system damage mode. However because of the complicated loading condition, the friction between indenter and coating, nonlinear elastic-plastic behavior of coating and substrate, it is difficult to make the stress distributions respectively getting from the numerical analysis and scratch test coincident. There is no completely correct theorietical model to predict the stress in the coating composites when it is loaded by a moving indenter. Numerical simulation is the only method to get the stress distribution of a nonlinear model in scratch test. Internal stress in the coating is also the important factor to determine the stability and life. And it will also limit the thickness of the coating. It is found that residual stress is mainly caused by phase transformation in the deposition process. Researches on the coating phase transformation have not been mature enough. And there is no specific method to describe the volume chang of phase transformation for coating.By taking into account of the interface damage, coating damage and substrate damage, scratch tests of single soft coating, single hard coating and automobile multiple coatings were simulated. DLC coating was deposited on Si substrate by PCVD method. And phase transformation coefficient a was defined to investigate the material deformation caused by phase transformation. And the finite element simulation results were compared with the tests results. The nano-scratch tests of resin matrix composites without nano-coating and with nano-coating were performed to get the surface properties. It was discussed that the nano-material could be used to improve the surface properties. Nano-material was added into the automobile paints. The mechanics properties of automobile paints with nano-material were discussed.The following conclusions were obtained in this paper:1. Elastic modulus, ultimate strength and other mechanics properties of the paint materials were gotten from the tensile testing. By taking into account of the interface damage, coating damage and substrate damage, scratch tests of single soft coating, single hard coating and automobile multiple coatings were simulated by FEA. The results such as the interface strength, the damage occurring and developing, the damage modes, etc were gotten from the simulation. The simulation results were compared with the test results. The critical load was close to the scratch test result.2. DLC coating was deposited on Si substrate by PCVD method. And phase transformation coefficientαwas defined to investigate the volume deformation caused by phase transformation in this process. The residual stress in the coating was mainly caused by the phase transformation. The residual stress in the coating depended on phase transformation coefficient and elastic modulus of coating material together. When the value of a x E was bigger, the corresponding residual stress was bigger.3. Hardness and scratch resistant performance can be enhanced greatly if the resin matrix composites were coated with the nona-materials. When nano-material was added into the automobile coatings, the function of coupling agent was obvious. The mechanics properties of the paints were improved by adding both coupling agent and nano-particles into the composites.