| Recently,carbon fiber reinforced polymer(CFRP)composites have gained substantial interest and been widely used in fields of aeronautics and automotive for their favorable strength-to-weight and stiffness-to-weight ratios.However,short forming time,drastic physical and chemical reaction of the rapid forming technology have more efficient influence on the interphase in the carbon fiber reinforced resin matrix composites,for the formation of the chemical and mechanical bonding between the fiber and the resin.In this study,fast curing epoxy and polyamide were chosen to learn the effect of the rapid forming technology.The strain history of the fast curing epoxy matrix composites induced by chemical shrinkage and temperature history considering exothermal reaction were measured by Fiber Bragg grating sensors(FBGs).The thickness and properties of the interphase in the fast curing epoxy matrix composites and the polyamide composites were quantitatively characterized by Peak Force Quantitative nanomechanical property mapping(Peak Force QNM).Changes of interfacial thickness and short-beam strength of the fast curing epoxy matrix composites and the polyamide composites in hydrothermal aging process were recorded.Then relationships among the rapid forming properties of the fast curing epoxy and the polyamide,the interfacial properties and the hydrothermal properties of their composites were analyzed.Compared with the properties of conventional curing epoxy matrix composites,the effect of the rapid forming technology on the interfacial properties and the hydrothermal properties of the rapid forming composites were summarized.The intense heat from drastic exothermal reaction and the short curing time of the fast curing resin have more efficient influence on gradient of temperature and distribution of degree of cure than the conventional curing resin,which has a significant affection on interfacial properties of the composite by the level of cure residual strain(CRS).The cure residual strain in the 1st ply of the fast curing composite was-5183.3??,while that in the conventional curing composite was-2975.9 ??.The interphase in the fast curing epoxy matrix composites in modulus image was found to be soft with an average thickness of 20.03 ± 2.04 nm,while it was 40.48 ± 4.17 nm in the conventional curing epoxy matrix composites.Consistent with the interphase thickness determined by the modulus,the average interphase thickness in the fast and conventional curing epoxy matrix composites were 19.45 ± 0.68 nm and 41.01 ± 3.98 nm,respectively,based on the adhesion contrast in the interphase.Compared with the conventional curing epoxy matrix composites,the modulus and the adhesion of the interphase changed more sharply in the fast curing epoxy matrix composites.Because of the drastic exothermal reaction,short gelation time and short curing time of the fast curing epoxy resin,the formation of the chemical and mechanical bonding in the interphase in the carbon fiber reinforced fast curing epoxy matrix composites was drastic and rapid,and was limited in a narrow space after gelation.In hydrothermal aging process,with the addition of time,a significant decrease in the short-beam strength of the composites was recorded.The short-beam strength of the fast curing epoxy matrix composites was 37.64 MPa after 192 h of hygrothermal aging,decreased 15.01%,while that of the conventional curing epoxy matrix composites was35.71 MPa after 312 h of hygrothermal aging,decreased 16.25%.Compared with conventional curing epoxy matrix composites,the properties of the thinner interphase in the fast curing epoxy matrix composites with bigger CRS changed more sharply,leading to voids and microcracks in the interphase easily.Therefore,the interphase in the fast curing epoxy matrix composites was enriched with more water,causing microcracks propagation and interfacial debonding earlier.The short forming time,high viscosity,physical reaction,crystallization of the polyamide in rapid hot molding have more efficient influence on the formation of physical bonding and transcrystallizaiton in the interphase in the polyamide composites by rapid hot press molding.Then,from the carbon fiber to the polyamide matrix,the modulus of the interphase in the polyamide composites by rapid hot press molding decreased gradually,while the adhesion increased gradually,which was different from the conventional curing epoxy matrix composites.And the interphase thickness in the polyamide composites by rapid hot press molding in modulus image was 72.17 ± 6.19 nm,it was 71.80 ± 7.51 nm based on the adhesion contrast in the interphase.In hydrothermal aging process,the short-beam strength of the polyamide composites by rapid hot press molding was 78.29 MPa after 24 h of hygrothermal aging,decreased 26.78%.The interphase in the polyamide composites by rapid hot press molding was easy to break in hydrothermal aging process because of the formation of physical bonding and transcrystallizaiton,leading to sharp decrease of the short-beam strength of the polyamide composites by rapid hot press molding. |
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