Analysis of methyl methacrylate adhesive (MMA)relaxation with non-linear stress–strain dependence

One of the problems regarding high strength and stiffness adhesive connections is the concentration of stresses on the edges of the bond. The use of adhesives characterized by high strength but also greater flexibility would avoid this effect and prevent brittle failure. Therefore, the results of a series of laboratory tests are presented in the paper for a semi-rigid methyl methacrylate adhesive (MMA). The research included quasi-static tensile and relaxation tests of the adhesive at a temperature of 23 °C and 50% humidity. Based on the test results, the complex characteristics of the viscoelastic material parameters of the adhesive for different stress levels were determined. The Maxwell model was used to describe the material model of the adhesive during relaxation, for which Prony series were calculated. The work also indicates the approach to numerical modelling using the Finite Element Method (FEM)for selected adhesive, ensuring good convergence of results in the elastic work of the material. Numerical analyses were performed in the ABAQUS software, using material models such as hyperfoam and viscoelasticity. Finally, the relaxation function values obtained during the laboratory tests and numerical analyses were compared and a forecast for longer term function values was presented. The presented results can be used for numerical analysis of adhesive joints with the use of a selected methacrylate adhesive, in the scope of the elastic range subjected to short- or long-term loads.