PSI - Issue 14

P R Krishna Mohan et al. / Procedia Structural Integrity 14 (2019) 176–183 P R Krishna Mohan/ Structural Integrity Procedia 00 (2018) 000–000

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Fig.5. FTIR analysis: Plasma treated sample kept in vacuum

4.6. Comparison of the strength of the laminates

From the literature reported in Table 3, the strength of 0° laminate made of carbon/epoxy found to be in the range of 1235.7 MPa to 2000 MPa. The average strength of the successfully tensile tested composite sample made of in house vacuum treated prepreg is obtained as 1750.32 MPa showing a satisfactory strength. However, the strength values shown in literature depend upon many factors such as the grade of carbon fiber and epoxy used and the fiber volume fraction of the composite.

Table 3.Comparison of strength and modulus of composites made of in-house prepregs with available literature Specimen Property 0 ° 90 ° [ ± 45] S In-house Non-vacuum Strength (MPa) 966.48 8.36 177.07 - Modulus (GPa) 72.74 - 9.51 In-house Vacuum ( v f 45%) Strength (MPa) 1750.32 - - - Modulus (GPa) 78 - - Schwartz [9] Strength (MPa) 1450 62 - - Modulus (GPa) - - - Reddy et al. [8] Strength (MPa) 1235.7 11.25 - (T-700 carbon fiber/ v f 65%) Modulus (GPa) 134.58 8.12 -

5. Conclusion

The present work involves the modification of the prepreg machine to improve the strength of the in-house prepreg sheets. After modifying the prepreg machine, B-stage curing in the vacuum and non-vacuum environment at room temperature, has been carried out. The tensile tests were performed on laminates made of three different fibre orientations as per the ASTM standards. TGA test was performed to evaluate the fibre volume fraction. Further, plasma treatment is carried out on carbon fibres, and FTIR analysis is performed to identify functional groups. The following summarizes the present work. • The 55.39% increase is observed from the previous strength for non-vacuum0 ° laminate. • For the case of vacuum prepreg laminate, there is 56.81% increase in the strength compared to the strength obtained from the non-vacuum 0 ° laminate.