The purpose of this study is to investigate the influence of sizing treatment of carbon fiber surface on apparent interfacial adhesive shear strength（ IFSS） between fiber and matrix under high strain rate condition. Model composite specimen with single fibers was prepared with carbon fiber as the reinforcement and thermoset epoxy resin as matrix, respectively. The observed IFSS was measured by fragmentation test. The dynamic tensile load was applied to the specimen by using an apparatus of tensile-type split Hopkinson pressure bar. Test results showed that the observed IFSS between sized carbon fiber and matrix was increased compared with that between un-sized carbon fiber and matrix when static tensile load was applied. As the applied strain rate was increased, the effect of the sizing treatment on the IFSS was not significant. The results also showed that the observed IFSS was decreased due to change of the distribution of fiber fragmentation length accompanying with the change of the morphology of carbon fiber breakage due to the generation of compressive elastic stress wave after breakage. It was also found that the influence of the generation of compressive elastic wave on the IFSS was more dominant than that of sizing treatment to determine the observed IFSS between carbon fiber and epoxy resin under high strain rate condition.

Epoxy resins with oxazolidone ring （Oxa-E） are expected for structural adhesives because of their good thermal stability. The evaluation of the fatigue crack propagation resistance is required for structural adhesive joints from a viewpoint of long-time reliability and damage tolerance design. The aim of this paper is to investigate the effect of addition of oxazolidone ring into epoxy networks on the fatigue crack propagation properties of the adhesive joint. Epoxy resin with oxazolidone ring was mixed into bisphenol-A diglycidyl ether（DGEBA）． Two types of toughening agents, polyamide particles and core-shell rubber particles, were used. Graphene nanoplatelets were used as sacrifice particles which lead to cohesive fracture. The fatigue crack propagation tests were conducted using tapered double cantilever beam （TDCB） specimens. The optimum content of the graphene nanoplatelets was found to be 0.16wt％ , which shows the cohesive fracture and the highest crack propagation resistance. The adhesive with Oxa-E had the superior fatigue crack propagation resistance to the DGEBA adhesive which has equivalent glass transition temperature and lower molecular weight between crosslinks. On the other hand, it has the similar crack propagation resistance to the DGEBA adhesive which has equivalent molecular weight between crosslinks. These results agreed well with the results of the bulk resin. The adhesive with both heat resistance and long life was achieved by inserting the epoxy with the oxazolidone ring into epoxy network.

In recent years, the direct adhesion of fluoropolymer to other materials has received much attention, especially in micro-electronic field due to their outstanding dielectric properties, flexibility, chemical and thermal stability which are suitable for insulating substrate of print circuit board for providing ultrahighspeed internet. One of the biggest characteristics for fluoropolymers is low surface energy which make it quite difficult to adhere to other materials without any surface modification treatment. Until now, some unique and valuable methods improving adhesive properties of fluoropolymers have been investigated and developed for manufacturing lots of fluoropolymer-based products. In many cases, adhesives are essential to bond fluoropolymers and other materials, even though its surface has been hydrophilized. However, it is requested that the fluoropolymers are directly adhere to the other materials including metals, plastics, rubbers, and elastomers without any glues today, in order to adjust to higher functionalities and environmental regulations which are listed in SDGs. Herein, we review the surface modification technologies from the old wet process basing upon chemical reaction to the later dry process involving several types of plasma treatment, and finally introduce our recent work about plasma-induced surface modification of fluoropolymers and its direct adhesion to profile-free Cu foils.