PSI - Issue 14

C.Jayarami Reddy et al. / Procedia Structural Integrity 14 (2019) 634–641 C.Jayarami Reddy/ Structural Integrity Procedia 00 (2018) 000–000

636

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probes and signal conditioners were from M/s. PCB-Piezotronics Ltd., USA. The oscilloscope Model DPO5104B of M/s.Tecktronix was used to record the pressure profiles. The diameter of H-glass fibre was estimated using scanning electron microscopy (SEM) (Make: LEO, UK; Model 440).The SEM depicting the cross sectional view of the fibre is shown in Fig. 1(a). The inner (3.56μm) and external (10.52μm) diameters of the fibre were estimated using the SEM images shown in Fig. 1(b) and 1(c), respectively.

Fig. 1. SEM images of (a) cross sectional view of fibres; (b) internal diameter of fibre; (c) external diameter of fibre.

2.2. Fabrication of H-glass and E-glass composite laminates The 1556 resin and 1972 hardener were taken in 100:60 weight ratio and mixed for few minutes to form uniform mixture. Then the H-glass and E-glass woven rovings were coated with resin mixture uniformly. These coated rovings were dried at room temperature for 1 hour to prepare respective glass/epoxy prepregs. Later, the prepreg was cut into pieces of 300 mm×300 mm. Suitable number of plies required for fabricating 3 and 5mm thick composites were stacked between teflon coated release films. The plies along with the release films were placed on the steel mould. The spacer rods were kept around the stack of plies to arrest the flow of resin and to maintain the thickness of composites. Mild steel plates weighing approximately 30 kgs were kept on the mould for compaction of the plies and no extra pressure was used in fabrication. The composite laminate was allowed to cure at room temperature for 20 hours. After curing, composite panels were removed and trimmed and cut into required sizes using diamond wheel cutting machine. 2.3 Physical and mechanical properties of composites The physical properties such as resin content and the density of H-glass and E-glass epoxy composites were evaluated using burn off test method and density measurement kit, respectively. Both these composites were also evaluated for their mechanical properties such as tensile strength, flexural strength, and inter laminar shear strength. All the tests were performed as per the ASTM standards. The specimens were cut using diamond wheel cutting machine. Six test specimens were used for every measurement and the average of the six tests was considered as the final result. The mechanical and physical properties of the composites are shown in Table 1.

Table 1. Physical and mechanical properties of H-glass/epoxy and E-glass/epoxy composites. Sl.No. Property Standard/method

H-glass/epoxy E-glass/epoxy

01 02 03 04 05

Density

Density measurement kit 1.3

1.7

Resin content (wt%) Tensile strength(MPa) Flexural Strength(MPa)

Burn-off test ASTM D 3039 ASTM D 790

22±1

22 ±1

150

290

56

82

Interlaminar shear strength (ILSS) (MPa) ASTM D 2344

5

8