The obtained data for both theoretical and actual density for different fabricated composite specimens is plotted in Fig. 3 (a, b). The plotted figure suggests that increase in silicon carbide filler leads to increase in both theoretical and actual density. The void fraction continues to increase with increase in filler content.
The tensile strength behaviour of the developed composites is presented in Fig. 4 (a, b). The obtained tensile strength signifies that the inclusion of SiC filler reduced the tensile properties of the SiC filler epoxy composites [figure 4 (a)]. For SiC filler composites, the composites with filler weight percentage more than 15% the rate of reduction of tensile properties were found to be more severe (in the range of 2.32–5.97%) than the other composites (in the range of 14.28–26.85%). This phenomenon occurred due to the inability of matrix material to withstand the load to resist deformation. A fibrous phase may be incorporated to enhance the tensile strength of the SiC filler ceramic epoxy composite. Further, woven glass fiber was incorporated and SiC filler – Glass Fiber reinforced hybrid epoxy composites were fabricated. The tensile properties of these composites found to be enhanced due to the excellent load bearing capacity of glass fibrous phase in the composite [figure 4 (b)]. However, From the Fig. 4 (b), it also can be observed that the addition of SiC filler with the epoxy resin beyond a certain range (15%) resulted in higher rate of deterioration (in the range of 1.67–3.16%) of tensile load bearing capacity as compared to other composites (in the range of 5.09–7.86%). This is due to the lack of stiffness of SiC ceramic filler leading to lower structural stability of matrix phase.
The flexural strengths of above-mentioned composite samples are presented in Fig. 5 (a, b). The flexural strength of the SiC filler epoxy composites deteriorated with addition of SiC filler because of poor interphase strength between matrix and filler phase. The rate of reduction of flexural strength of SiC filler composites lies in the range of 1.91%-23.03% [figure 5 (a)]. The addition of woven glass fibrous phase further enhanced the bending resistance of the SiC-GF hybrid epoxy composites. In case of SiC-GF hybrid epoxy composites, the rate of reduction was found to be within 2.45–6.74% [figure 5 (b)]. Similar type observations were found for both SiC filler and SiC-GF hybrid epoxy composites. The composites with more than 15% SiC filler exhibited more rate of deterioration of the flexural strength as compared to other composites. This may have occurred due to the increase of brittleness of the composites leading to more severe plastic deformation under flexural loading.
The impact strength behaviour of the tested samples is presented in Fig. 6 (a, b). The neat epoxy sample underwent severe damage during the application of impact load. The inclusion of SiC reinforcements improved the impact strength of the composites as compared to neat epoxy. Further, it was found that the composites with 30% SiC filler provided maximum resistance to impact loading among the tested specimens. The GF-SiC filler hybrid epoxy composites exhibited better impact strength due to the load bearing strength of glass fiber phase. The GF-SiC composites showed better impact strength as compared to the prior samples. This occurred due to resilience of GF phase to withstand more shock loads thus enhancing the impact bearing capacity of the hybrid composites.
The hardness values of the composites are plotted in Fig. 7 (a, b). The incorporation of SiC filler resisted the impregnation of indenter due to its strong crystalline structure. The SiC filler material resisted the plastic deformation of the material surface. However, the relatively softer matrix material i.e. epoxy plastically deformed and dent was observed on the composite surface. The addition of GF strengthens the material to absorb the applied load thus providing improvement on the surface abrasion resistance of the composites [figure 7(b)].
The thermogravimetric behaviour of SiC filler and SiC-GF hybrid composites are presented in Fig. 8 (a, b). During the gradual rise of temperature of the specimens, in the initial phase, the rate of weight change was observed to be very less. During the initial heating of samples, the moisture along with volatile substances present on the specimen got removed which resulted in lesser change of weight percent. This phenomenon can be seen approximately in the temperature range of 300C to 3000C. Beyond the temperature of 3000C, a steep rise in the weight reduction was observed for all the samples. In this range, the polymeric material started decomposing due to rise in temperature along with disbanding of filler-matrix phases of the composite specimen. Further rise in the temperature caused the thermal decomposition of filler phase. Similar behaviour was observed for both SiC filler and SiC-GF filler hybrid composites. However, it was noticed that, the hybrid composites exhibited better thermal stability as compared to the SiC filler composites. This happened due to the role of glass fiber in absorbing the heat to avoid thermal degradation of the composites. Beyond the temperature of approximately 5000C, the weight reduction percentage of the composites reduced drastically and reached a stagnant stage. The burnt remaining were of the burnt filler materials which further doesn’t decompose under the heat significantly.
Figure 9 (a, b) show the thermal conductivity value of both SiC filler and SiC-GF HPCs. Figure 9 (a) shows that if percentage of SiC increases then the value of thermal conductivity increases both mathematical models and experimental value. Furthermore, it can be noticed that thermal conductivity values of HPCs were of similar behaviour as of the SiC-epoxy composites [figure 9 (b)]. It was also observed that minimum deviation of experimental thermal conductivity values occurred with respect to the theoretical thermal conductivity values obtained from Maxwell model followed by Hashin’s model and Rule of mixture model. The inclusion of SiC filler to epoxy based composites contributed to more dissipation of heat inside the composite structure. This makes the composites more suitable for applications wherein heat dissipation plays a crucial role in determining the material property. The addition of SiC fillers facilitated the movement of heat energy inside the composite structure by providing pathways for transmission of heat energy. Increase in weight fraction of SiC filler further enhances the thermal conductivity of epoxy composites through surface-to-surface interaction. However, with higher weight percentages of SiC filler, poor dispersion of heat in the composites structure may occur due to the agglomeration of SiC fillers.