| Since carbon fiber composites are widely used in aerospace,medical equipment,automotive,and sporting goods,recycling carbon fiber composites has become an increasingly important issue.The recycling of carbon fiber focuses primarily on shortcut carbon fiber at present.In spite of this,the recycling of short-cut carbon fibers is primarily limited by three factors:(1)short-cut carbon fibers are easy to agglomerate into bundles;(2)the surface chemical properties are unstable;and(3)the mechanical properties of the body are poor.To address the above problems,this thesis focuses on the construction method of interfacial phase and its effect on the interfacial phase and mechanical properties of fibers and fiber/resin composites,as well as exploring the application of multi-size interfacial short fiber mats on resin-based composites.According to the research,the following results were obtained:1.Creating a "soft-phase" interfacial layer on the surface of carbon fiber.A softphase chitosan reinforcement(CS)was fabricated on the surface of carbon fiber(CF),and the interfacial and mechanical properties of CF@CS/EP composites were controlled by varying the degree of CS deacetylation.According to the results,the mechanical properties of CF@CS/EP increased with an increase in the degree of CS deacetylation.A CS deacetylation degree>90 could increase the interfacial shear property(IFSS),transverse fiber bundle tensile property(TFB)and monofilament tensile strength of CF@CS90 by 63.1%,27.7%,and 10.35%,respectively.The improvement in wettability is due to an increase in reactive groups on the surface of CF,such as amino and hydroxyl groups.2.The formation of "soft-stiff" interfacial layers on the surface of carbon fibers.On the surface of CF,a "soft-stiff" chitosan/carbon nanotube(CNT)multiscale interface layer will be constructed,and the effect of CNT graft density on the interface between CF@CS@CNT and CF@CS@CNT/EP composites will be studied.As a result,the tensile strength of monofilament carbon fibers and the IFSS of the composites reached their maximum values(6.01 GPa and 123.65 MPa,respectively)when CNT concentration was 0.05 wt.%,an improvement over CF@CS90 and its composites with 33.19%and 12.76%,respectively.CNT-induced crack deflection was attributed to the buffering effect of CS at the "soft-stiff" interface and the buffering stress of CS at the soft-hard interface.3.Preparation and performance evaluation of short-cut carbon fiber reinforced resin matrix composites.The fiber mat-reinforced resin matrix composites were prepared using a vacuum-assisted resin introduction method.The results showed that the ILSS,flexural strength and flexural modulus of CF@CS@CNT fiber matreinforced resin matrix composites were improved by 59.27%,81.82%and 45.79%,respectively.A new method is proposed in the paper for the construction of "soft-stiff"multiscale interfacial layers by examining the strengthening mechanism of short-cut fibers and composites,which provides a new pathway to the preparation of highperformance short-cut carbon fiber reinforced resin matrix composites. |
