PSI - Issue 14

Arun Kumar Singh et al. / Procedia Structural Integrity 14 (2019) 720–728 Arun Kumar Singh et al./ Structural Integrity Procedia 00 (2018) 000–000

723

4

Since the properties of the resin are very much dependent upon their chemical formulation along with the temperature processing condition, hence DSC has been chosen as an analytical tool for analysis of resins selected for fabrication of hybrid composite. The progress of the curing reaction and its softening behaviour has been investigated by Q200 differential calorimeter (TA Instrument). The graphs of DSC as shown in Fig.1 indicate that the melting temperature of both resins is around ~150 o C. The striking difference between the melting behaviour of both resins is in terms of associated enthalpy. In the DERAKANE 470HT-400, it is around ~ 98 J/gm while for PUR, it is around 194 J/gm. It indicates that the extent of crystallinity is quite high as compared to DERAKANE 470HT-400. Since the melting/softening temperature of both the resin is in the same range, hence both the resin may be processed in the same processing window. In this work, compression moulding techniques has been employed for preparing the composites, which contains stationary and movable moulds. UHMWPE/aramid lamina has been placed between them and then the mould was closed, heated and pressure was applied to obtain an evenly shaped composite. Applied pressure and heat during the moulding process depend on the thermal and rheological properties of the polymer. The hybrid composite were produced based on the design of experiment and they were classified into three levels with different pressure, temperature and time as given in Tables 1. 4. Flexural strength properties The flexural strength also known as bending strength is a measurement of strength of material to resist bi-axial deformation under transverse loading; while the flexural modulus is a measure of the resistance to bending deformation of the material. Flexural strength epitomizes the combined effects of a material’s basic tensile, compressive and shear properties. Material failure, then, is dictated by which of the three basic stresses is the first to reach its limiting value i.e., its strength which also roughly depends on the specimen geometry employed, especially the span length (Prasad, et al. (2005)).

Table 2. The Box-Behnken design with the actual values for three levels for the flexural strength of the hybrid composite. Run No. X1 X2 X3 Flexural Strength (MPa) Pressure (MPa) Temperature ( o C) Time (Minute) Exp. Predicted 1 (-1)13.7 (-1)123 (0)20 45.02 46.78 2 (+1)18.6 (-1)123 (0)20 33.78 42.40 3 (-1) 13.7 (+1)127 (0)20 77.65 69.02 4 (+1)18.6 (+1)127 (0)20 62.75 60.98 5 (-1)13.7 (0)125 (-1)15 46.31 49.73 6 (+1)18.6 (0)125 (-1)15 50.96 47.52 7 (-1)13.7 (0 125 (+1)25 50.42 53.85 8 (+1)18.6 (0)125 (+1)25 47.08 43.65 9 (0)16.2 (-1)123 (-1)15 49.46 44.27 10 (0)16.2 (+1)127 (-1)15 56.24 61.44 11 (0)16.2 (-1)123 (+1)25 46.36 41.15 12 (0)16.2 (+1)127 (+1)25 59.62 64.80 13 (0)16.2 (0)125 (0)20 69.11 69.11 14 (0)16.2 (0)125 (0)20 69.11 69.11 15 (0)16.2 (0)125 (0)20 69.11 69.11

In the present study, flexural testing was performed using a three-point bending method as per ASTM D790-03. Specimens were tested by Instran test machine (Model Instran 5967). The test specimen used is of size 125 mm