Effect Of Near Infrared Light Curing On The Strength Of GF/KH560-SiO₂/EP Composite Sheet And Temperature Field Simulation

With the growing market demand in China’s glass fiber（GF）composite industry,there is a need to optimize the mechanical properties of composite sheet by developing new resin matrix and new curing and molding processes.In this paper,the potential advantages of SiO₂nanoparticles are used to modify SiO₂ nanoparticles by adding silane coupling agent KH560to the epoxy resin（EP）matrix,so that KH560-SiO₂ can form a durable bond with the resin matrix on the glass fiber surface,and the curing characteristics and curing kinetics of the resin matrix are also discussed,and the non-isothermal DSC method is used to obtain the theoretical curing kinetic equations and The theoretical curing kinetic equation and optimal curing temperature profile were obtained by non-isothermal DSC method.The new curing and molding process uses near-infrared light as the heat source,and takes advantage of the excellent heat transfer effect of near-infrared light to irradiate the surface of the sheet directly,and the composite sheet makes full use of and absorbs the heat,so that its mechanical properties and productivity are improved.ABAQUS temperature field was used to simulate the step curing behavior of both the new near infrared light curing molding process and the traditional oven curing molding process,and to obtain the curing process correlation curves to study the thermal expansion and chemical shrinkage patterns during the curing process.Finally,on the basis of the optimal nano-SiO₂ addition to the composite sheet,the parameters of the near infrared light heating curing of different thicknesses of the sheet were debugged and optimized,and the SEM,FT-IR and Raman spectroscopy were performed at the fracture of the sheet fibers to analyze the mechanism of mechanical property improvement from both temperature and interface aspects,and the experimental results showed that:FT-IR and TGA analysis of KH560-SiO₂ nanoparticles showed that the silane coupling agent KH560 was successfully grafted onto the surface of SiO₂ nanoparticles by chemical reaction.Scanning electron microscopy revealed that the agglomeration of KH560-SiO₂ was significantly reduced and successfully dispersed into the resin matrix.Experiments showed that the curing process was smoother and most efficient when the curing agent content was16.6 wt%and the curing temperature was 90°C.The curing kinetic equation was determined by non-isothermal DSC method,and the theoretical curing temperature was 92℃,which was basically consistent with the experiment.（2）Finite element temperature field simulation results show that the composite sheet core temperature has a significant hysteresis phenomenon.The oven heating curing plate temperature gradient is large,the central node and the surface is difficult to reach the same temperature level in a short period of time,with a lower curing synergy.Near infrared light heating curing method of heat absorption and release process used in a shorter time,the thermal spike is more gentle,curing synergy is more excellent,the temperature consistency is better than the oven heating curing heat conduction effect.Near infrared light in the composite plate radiation depth of about 1 mm,the oven Radiation depth of about 0.3 mm,the difference in radiation depth is the fundamental reason for the different effects of the two curing methods.（3）Near infrared light heating curing temperature range of 130℃-150℃when the curing process is smooth and the best specimen morphology,4 and 16 layers thickness composite panels are not sensitive to the two curing methods,near infrared light curing 8 layers thickness composite panels will produce significant shrinkage effect,12 layers thickness composite panels curing process is not stable,the integrity has decreased.Composite panels added 3 wt%of KH560-SiO₂ The addition of 3 wt%of KH560-SiO₂ to the composite sheet results in an increase in tensile strength and a significant increase in elongation at break,and the deposition of KH560-SiO₂ on the surface of the glass fiber plays an important role in matrix cracking,delamination and fiber fracture.Near infrared light heating curing has a significant effect on the mechanical properties of composite panels with a thickness of less than 12 layers（2.65mm）,and SEM further reveals that this new curing and molding process enables more resin to adhere to glass fiber filaments,while oven heating curing resin adhesion effect is not obvious.FT-IR and Raman spectral analysis showed that near infrared light curing has good interfacial bonding properties,explaining the reason for more resin adhesion.Finally,the strength enhancement mechanism of the composite sheet was described from two perspectives of temperature field and interface.