PSI - Issue 14

Vivek Khare et al. / Procedia Structural Integrity 14 (2019) 215–225 Vivek Khare, Shubham srivastava, Sudhir kamle, G.M.Kamath / Structural Integrity Procedia 00 (2018) 000 – 000

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Fig. 5. Creep test results (a) Neat PP; (b) MWCNT-COOH-PP 0.5%; (c) MWCNT-Pristine-PP 0.5%; (d) MWCNT-COOH-PP 1%; (e) MWCNT-Pristine-PP 1%; (f) MWCNT-COOH-PP 2%; (g) MWCNT-Pristine-PP 2% nanocomposites

Creep compliance verses time curves were shown in Figure. 5 obtained from lower (0.2 MPa) to high (15 MPa) stress levels for 500 seconds of loading. Creep strain was found to be maximum for 1% MWCNT-COOH-PP while minimum for 0.5% MWCNT-PP as given in Table. 5. Threshold of stress and time for prediction of linear viscoelasticity was obtained by plotting creep compliance verses time curves. Linearity in material is determined by the extent up to where creep compliance curves were superimposed to each other independent of stress levels. It was observed that up to 1 MPa and 5 seconds of loading, the material remains in linearity limit. This was further validated by conducting cyclic tensile tests on functionalized MWCNT nanocomposites. Materials were tested for 5 cycles of loading at 1 MPa and unloading for 5 seconds each. Results shown in Figure. 6. clearly indicates superimposed loading and unloading curves. However 2% sample exhibits some offset in loading and unloading cycles.

Fig. 6. Cyclic test results (a) Neat-PP; (b) 0.5 % MWCNT-COOH-PP; (c) 1 % MWCNT-COOH-PP; (d) 2 % MWCNT COOH-PP nanocomposites