Mechanism Analysis of the Influence of Adhesive Layer on Scratch Damage of Polymethylmethacrylate Coating
To investigate the influence of adhesive layer thickness and adhesion strength on the scratch damage of polymethylmethacrylate(PMMA)coating,scratch experiments were systematically conducted on PMMA coatings with different adhesive layer thicknesses and adhesion strengths.A constitutive model considering the competition between shear yielding and brittle fracture was employed to describe the me-chanical behavior of PMMA coating.The scratch behavior of PMMA coating was simulated using the finite element method.The physical mechanisms behind the complex scratch damage modes were revealed.The results show that,different from the coating structures with a zero-thickness adhesive layer,the deforma-tion of the finite-thickness adhesive layer leads to local bending of the PMMA coating,resulting in the for-mation of internal cracks in the bottom region of the coating beneath the scratch tip.An adhesive layer with strong adhesion strength restricts the deformation of the coating during scratching,preventing severe buckling of the coating in front of the scratch tip and avoiding the formation of longitudinal cracks that penetrate through the coating along the thickness direction.Increasing the coating thickness can enhance the resistance of the coating to bending and buckling during scratching,thereby delaying the formation of the internal and longitudinal cracks.These findings contribute to the understanding of the scratch mecha-nism and further improvement of the scratch resistance and functional integrity of PMMA coatings.
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