PSI - Issue 14

724 Arun Kumar Singh et al. / Procedia Structural Integrity 14 (2019) 720–728 Arun Kumar Singh et al./ Structural Integrity Procedia 00 (2018) 000–000 5 length, 10 mm width and 5 mm thick and these were prepared by water jet cutting machine. Specimens were tested at the cross head speed of 10 mm/min at a temperature 23 o C and humidity of 50%. Flexural strength ( σ � ) was determined using the eq. (1) � � � ������� (1) Where, P is the maximum load, L is the span length, b and t are the width and thickness of the specimen, respectively. All tests were performed in triplicate and an average value of those three tests was taken as the representative value for the optimization of the process conditions. The flexural strength of the hybrid composite synthesized at different temperature, pressure and time (shown in Table 2) were obtained and the observed results were used to get the regression eq. (2).The flexural strength of the hybrid composite synthesized at different temperature, pressure and time (shown in Table 3) were obtained and the observed results were used to get the regression eq. (2). All tests were performed in triplicate and an average value of those three tests was taken as the representative value for the optimization of the process conditions. � � ��.11 � �.1�� � � 1�.��� � � �.��� � � �.�1� �� � 1.��� �� � 1.�� �� � �.��8 � � � �.�41 � � � 11.148 � � (2) Using multiple linear regression analysis, the set of coefficients for its flexural strength was calculated using the designs of experiments. The Design Expert 10.1 software has been used to optimize the process parameters involved in compression moulding parameters for obtaining better flexural strength of hybrid composite. By applying the model equation, an optimum flexural strength value of the order of 63 MPa has been obtained at 120 o C, 12.7 minutes and 14.2 MPa. 4. Fracture toughness properties 4.1 Effect of notch root radius on mode-I apparent fracture toughness The effect of notch root radius on fracture toughness has been extensively studied and reported by various researchers (Damani et al. (1996), Eugenio et al. (1999), Lagace et al. (1986), Ozcoban (2010) and Picard (2006)). But the similar study for p-aramid and UHMWPE based hybrid composite has not been found reported in literature. Before evaluation of fracture toughness of a material, it is one of the important requisite to evaluate the notch root radius effect. The actual fracture toughness of any material leads to erroneous due to inappropriate development of notch root radius. Thus, the creation of appropriate size notch as defined by notch root radius is very much essential to evaluate the fracture toughness. Evaluation of critical notch root radius will help to find the fracture toughness of the material.

Fig.2. Load vs. displacement curve obtained during flexural testing of hybrid composite specimen.