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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attributed to the retrofitting on prepreg machine with dip rollers, squeeze roller and oil bath circulation system that will maintain the low viscosity of the epoxy mixture and therefore improve the wettability of the fibers.

Fig.1. Load vs. Position for 0° laminate: a. Vacuum, b. Non-vacuum.

Fig.2. SEM Images: a. Before modifications, b. After modifications

4.2. Tensile test for 90° laminate Tensile tests were performed on 90° laminate prepared with prepregs B-stages at room temperature. A typical force-displacement curve is shown in Fig. 3a. A representative microscopic image of the failed sample under tension test is shown in Fig. 3(b) and (c), respectively, and it is observed that the failure mechanisms are mainly matrix cracking and delamination. The average strength of 8.36 MPa is obtained, with a maximum of 10.1 MPa and a minimum of 6.75 MPa as reported in Table 1. The low strength may be attributed to the burrs on the sample formed during the cutting. 4.3. Tensile test of [±45] S composite Tensile tests were performed on [±45] S laminate prepared with prepregs B-stages at room temperature. A typical load-displacement plot is shown in Fig. 4. The average strength and axial modulus of 177.07 MPa and 9.51 GPa, is obtained, with a maximum of 181.86 MPa and 9.73 GPa and a minimum of 152.94 MPa and 9.1 GPa, respectively as reported in Table 1. From the microscopic images shown in Fig. 4(b) and (c), respectively, the failure mechanisms like multiple ply cracking; internal delaminations are observed in the cracked samples.