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

722

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2. Design of experiments (DoE) Box-Behnken design of experiments and response surface methodologies are the most recent and efficient mathematical tools which are widely used for analyzing and controlling the effects of processing parameters of any engineering problem. These methodologies are comprehensive described in the literature (Vairamani et al. (2013), Aslan et al. (2006), Manohar et al. (2013), Box et al. (1960), Box et al. (1959), Annaduraiet al. (1998) and Box et al. (1957)). For the three level three factorial Box-Behnken experimental design, a total of 15 experimental runs were needed to determine the coefficients in the response surface equation. Table 1 shows the number of independent variables chosen for the study. The levels of variables like pressure, temperature and time were chosen based curing/processing behavior of resins selected for hybrid composite. The levels of each variable were defined here as -1, 0 and +1 for low, middle and high level respectively. The proposed model requires 15 runs for modeling of response surface.

Table 1. The level of variables chosen for Box-Behnken. Variable Symbol Limit Low (-1) Middle (0)

High (+1) 18.6

Pressure (P) MPa Temperature (T) o C Time ( ɒሻ Minute X3 X1 X2

13.7 123

16.2 125

127

15

20

25

3. Materials and moulding of hybrid composite The criterion for the selection of materials for structural applications is the maximum reduction in mass while maintaining aspects of its safety, functional requirements and minimum cost. Based on an analysis of the availability of new materials for structural applications such as ballistic armour, Dyneema HB80, a prepage material of UHMWPE fibres and Twaron CT750, a plain woven fabric material of p-aramid fibres has been chosen for fabrication of hybrid composite in this work. Keeping in view of constituent of fabric used in hybrid composite, Vinyl ester based DERAKANE 470HT-400 resin with TRIGONOX 239 A, catalyst has been selected for Twaron CT750 fabric while Dyneema HB80 comes in prepage form coated with polyurethane (PUR) resin for the fabrication of the hybrid composite. The Differential Scanning Calorimetry (DSC) plots of PUR and DERAKANE 470HT-400 resins are shown in Fig.1.

(b)

(a)

Fig. 1. DSC curves of resin (a) DERAKANE 470HT-400 and (b) polyurethane.