Characterization of the mechanical properties and thermal conductivity of epoxy-silica functionally graded materials

A functionally graded material (FGM) was prepared using epoxy resin reinforced with silicon dioxide with a particle size of 100 μm and weight percentages of 0, 20, 40, 60, and 80 wt%. In a gravity-molding process using the hand layup technique, specimens with international standard (ASTM)-calculated dimensions were created in a mold of poly(methyl methacrylate), which is also known as acrylic. Tensile, flexural, impact, infrared wave, and thermal conductivity tests, and X-ray diffraction (XRD) were conducted on specimens of the five layers of the FGM. The XRD and infrared spectroscopy demonstrated that the compositions of the silica particles and epoxy had a strong association with their physical structures. The findings of experimental tests indicated that increasing the ratio of silicon dioxide enhanced the mechanical properties, and the increase in modulus of elasticity was directly related to the weight percentage of the reinforcement material. The composite with 80% silica had a 526.88% higher modulus of elasticity than the pure epoxy specimen. Both tensile and flexural strengths of the composite material were maximal when 40 wt% of the particle silicon dioxide was utilized, which were 68.5% and 67.8% higher than those of the neat epoxy, respectively. The test results also revealed that the impact resistance of the FGM increased when the silica proportion increased, with a maximum value of 60 wt% silica particle content, which was an increase of 76.98% compared to pure epoxy. In addition, the thermal properties of epoxy resin improved when SiO2 was added to the mixture. Thus, the addition of silica filler to composite materials directly proportionally increased their thermal conductivity to the weight ratio of the reinforcement material, which was 32.68–383.66%. FGM composed of up to 80% silica particles had the highest thermal conductivity.