The application of central composite rotatable design to model and optimize the tensile strength of " composite- steel" connections

In the present study، central composite algorithm was used in order to model and optimize the mechanical behavior of “glass fiber reinforced epoxy composite - structural steel “connections. Initial tests showed that the polymer curing variables play a significant role as key process parameters in producing strong and reliable connections. After conducting Thermal Gravimeteric Analysis on polymer، by selecting curing time and curing temperature as input variables، the parameters were coded and each of them was studied in five levels. In order to estimate the desirable response and provide appropriate models، thirteen tests were conducted systematically. In order to assess the accuracy and to validate the proposed model، analysis of variance was performed successfully. The effect of curing time and curing temperature on the connection’s strength quality was studied utilizing two-dimensional graphs. Utilizing this approach the optimal bonding process variables was achieved at 40°C and 180 min for curing temperature and curing time respectively. Finally، the results obtained from micro structural characterization and fractography analyses of joints by Optical and Scanning Electron Microscope were in good agreement with the results achieved by the developed model.