Cryogenics performance enhancement of epoxy resin composites through negative expansion nanomaterials: Mechanism and predictive modeling

The matrix cracking of carbon fiber reinforced epoxy resin based composites (CFRPs) at cryogenics (such as liquid nitrogen temperature) is a major issue affecting the normal operation of deep space and deep-sea detectors, as microcracks caused by the thermal residual stress of both can reduce the structural integrity of the devices. In this work, we report an epoxy (EP) nanofiller CuO nanorods (CuO NRs) with negative thermal expansion properties at cryogenics. Experiments showed that CuO NRs can effectively inhibit the shrinkage of EP at cryogenics and improve the mechanical properties of EP at cryogenics. A temperature dependent prediction model for the tensile strength of EP/CuO NRs was proposed, and the predicted results were in good agreement with experimental results. Finally, through a combination of experiments and theory, it was demonstrated that the tensile strength of EP/CuO NRs at cryogenics is jointly enhanced by the enhancement effect of the nanomaterials and the axial compressive thermal residual stress between EP and CuO NRs. Highlights: Successfully prepared CuO nanorods with negative expansion properties at low temperatures, and found that they can effectively inhibit the shrinkage of epoxy resin at cryogenics. At cryogenics, the expansion of CuO nanorods enhances their interface effect with epoxy resin and improves the tensile strength of epoxy resin composites. The theory of tensile strength of epoxy resin at cryogenics was proposed for the first time. Theoretical analysis shows that the low temperature residual thermal stress between CuO nanorods and epoxy resin is the main factor to improve its tensile strength.