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In the electronics and aerospace industries, epoxy resins are generally regarded as economical and efficient adhesives and have a high status. However, epoxy resins are highly crosslinked polymers and are very brittle adhesives where they are prone to fast crack propagation under dynamic loads. Therefore, it is very necessary to enhance the toughness of epoxy resin adhesives. Nano-rubber has been proved to be an important toughening agent for epoxy resin, which can significantly improve the fracture toughness of epoxy resin. However, increasing the toughness of epoxy resin by adding nanomaterials is often accompanied by decreasing the strength and stiffness of resin. Therefore, in this work, rigid nano-silica particles were added to improve the rigidity and tensile strength reduction caused by the addition of rubber particles. And further increase the toughness of the epoxy resin to obtain an epoxy adhesive with balanced stiffness-toughness. As a result, it can be found that the addition of silica particles can significantly improve the decrease in stiffness caused by the addition of rubber particles. For example, Young's modulus and tensile strength are increased by 28%, and 23%, respectively, with 4% silica is added based on rubber particles. Through the single lap shear experiment, it is found that the shear strength of the epoxy/RnP/silica composite adhesive has increased, which further proves that the addition of nano-silica particles can increase the stiffness of the epoxy composite. The dynamic mechanical analysis experiment found that after adding nano-silica particles, the storage modulus of epoxy composites increased, which also shows that adding nano-silica particles can improve the stiffness of epoxy composites. Scanning electron microscopy analysis was performed to study the reinforcement mechanism of epoxy/RnP/silica composite materials. The thermal stability of epoxy composites was characterized by Dynamic mechanical analysis and thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Graphene platelets (electrically conductive 2D filler) and rubber nanoparticles (0D soft filler) can work together to develop electrically conductive and toughened epoxy composite adhesives. In this study, complementing effect between graphene platelets (GnPs) and rubber nanoparticles (RnPs) within an epoxy matrix is reported. In the 3‐phase composite adhesive, the 2D graphene platelets form global conductive network and rubber nanoparticles provide a viscoelastic phase inside the epoxy, both complementing each other to develop electrically conductive and toughened epoxy composite adhesives. Fracture toughness (K1c) and critical strain energy release rate (G1c) of the epoxy were augmented by 422% and 872%, respectively by adding 1 wt% RnPs and it recorded electrical percolation threshold at 0.78 vol% GnP. Also, the Young's modulus and strength of epoxy/1 wt% RnP composite were promoted from 1.57 to 2.32 GPa when 1 wt% GnP is added. Scanning electron microscopy analysis was conducted to investigate the toughening mechanism of epoxy/RnP/GnP and epoxy/GnP composites. Lap shear strength tests on epoxy composite adhesives confirm the reinforcement effect of GnPs and toughness effect of RnPs. [ABSTRACT FROM AUTHOR]