Toughness Effect of Graphene Oxide-Nano Silica on Thermal-Mechanical Performance of Epoxy Resin

A graphene oxide/nano-silica(GOS)hybrid was rapidly and easily synthesized using graphene oxide(GO)and nano-silica(nano-SiO_(2))as raw materials,and the synthesized GOS was used to improve the mechanical properties of epoxy resin(EP).The modified EP with different mass fractions of GOS(0,0.1%,0.2%,0.3%and 0.4%)were prepared and studied.The structure,thermal stability,mechanical properties,fracture toughness and failure morphology of the modified EP were analyzed.The results showed that the tensile strength of GOS modified EP increased from 40.6 MPa to 80.2 MPa compared with EP,the critical stress intensity factor of GOS modified EP increased by 65.9%from 0.82 MPa·m^(1/2)to 1.36 MPa·m^(1/2),indicating a significant enhancement in fracture toughness.In addition,failure morphology was observed by scanning electron microscopy(SEM)observation.The toughness mechanism of the modified EP was also discussed.Finally,the thermal stability of the modified EP was improved by the addition of GOS.Compared with neat EP,the initial thermal degradation temperature and glass transition temperature of GOS modified EP increased by 4.5℃and 10.3℃,respectively.

Calotropis gigantea Fiber‑Based Sensitivity‑Tunable Strain Sensors with Insensitive Response to Wearable Microclimate Changes

Wearable tensile strain sensors have attracted substantial research interest due to their great potential in applications for the real-time detection of human motion and health through the construction of body-sensing networks.Conventional devices,however,are constantly demonstrated in non-real world scenarios,where changes in body temperature and humidity are ignored,which results in questionable sensing accuracy and reliability in practical applications.In this work,a fabric-like strain sensor is developed by fabricating graphene-modified Calotropis gigantea yarn and elastic yarn(i.e.Spandex)into an independently crossed structure,enabling the sensor with tunable sensitivity by directly altering the sensor width.The sensor possesses excellent breathability,allowing water vapor generated by body skin to be discharged into the environment(the water evaporation rate is approximately 2.03 kg m^(-2) h^(-1))and creating a pleasing microenvironment between the sensor and the skin by avoiding the hindering of perspiration release.More importantly,the sensor is shown to have a sensing stability towards changes in temperature and humidity,implementing sensing reliability against complex and changeable wearable microclimate.By wearing the sensor at various locations of the human body,a full-range body area sensing network for monitoring various body movements and vital signs,such as speaking,coughing,breathing and walking,is successfully dem-onstrated.It provides a new route for achieving wearing-comfortable,high-performance and sensing-reliable strain sensors.