Mechanical behavior and optimization of constitutive prediction model for Epoxy/Al energetic composite materials considering temperature and strain rate effects

Abstract

Epoxy/Al as a functional structural energetic composite material that can be used as an adhesive, energetic fragments and warhead shells due to its high energy density, low density, and high strength. It can release a large amount of chemical energy (about 21.36 kJ/g) through chemical reactions when subjected to high-speed impact and thermal stimulation. Whether used as a matrix or auxiliary component, it has enormous development potential. Therefore, it is particularly important to study the mechanical properties of Epoxy/Al energetic composite materials under different temperature environments and strain rates of loading. This article describes the preparation of Epoxy/Al specimens with a mass percentage of 70%–30% using vacuum curing after 24 h under 0.8 Bar and 50 °C. The mechanical properties of Epoxy/Al specimens under different loading conditions were characterized using a high and low temperature universal testing machine and a separate Hopkinson experimental system. The modulus prediction method of binary composite materials was improved by combining SEM (scanning electron microscopy) and microstructure, and an adaptive constitutive model was developed combined with the K Srinivas model and neural network model based on the Sherwood Frost empirical constitutive relationship. The results show that Epoxy/Al energetic composite material has a significant temperature effect. When the temperature exceeds 100 °C, Epoxy/Al energetic composite material will be a significant physical and chemical property transition (the specimen exhibits viscous fluid characteristics and gradually begins to slowly decompose). As the temperature decreases, the specimen gradually exhibits a certain degree of brittleness and strength is improved. Due to the deformation, displacement, and interfacial debonding of internal particles during the loading process, Epoxy/Al materials exhibit excellent impact energy absorption effects, with energy absorption reaching 15.30 MJ/m3 at room temperature, and unit mass cost much lower than popular CFRP (carbon fiber-reinforced polymer) materials (CFRP energy absorption cost is 0.268 J/g/£, while Epoxy/Al materials do not exceed 0.013 J/g/£). During the dynamic loading process, Epoxy/Al energetic composite materials exhibit a phenomenon of structural reconstruction and enhancement throughout the entire loading process. The maximum strength at room temperature can reach 240.70 MPa, which is superior to all existing energetic materials of the same type. By introducing interface effects and quantifying them in the Halpin Tsai model, the existing prediction method for the Young's modulus of binary particle added composite materials has been effectively improved, reducing the prediction error of the Young's modulus of Epoxy/Al energetic composite materials from 14.2% to 2.4%. The numerical simulation results indicate that the newly developed constitutive model has high accuracy and can better reflect the mechanical properties of Epoxy/Al materials. The development method of this constitutive model has a positive contribution to the development of composite materials.