The fiber reinforced composite is composed of fiber, which is a reinforcing material, and resin, which is a matrix material. Good physical properties of fiber reinforced composites depend strongly on the interfacial properties between fiber and resin. When the interfacial adhesion force is good, the load is uniformly distributed inside the material and the toughness is obtained. However, when the interfacial adhesion force is low, cracks are generated at the interface and the material is failed. Therefore, the interfacial properties affect the physical properties and the reliabilities of fiber reinforced composites. The interface needs to be defined physically and chemically.
The microbond test is widely used to evaluate the interfacial properties of fiber reinforced composites. In the case of thermoplastic resin, it has a property of being extremely vulnerable to oxidation and thermal decomposition. The problem in the microbond test is data with an inaccurate and high distribution depending on thermal decomposition and droplet shape. In order to obtain complete data and accurately evaluate interfacial properties, it is necessary to minimize thermal decomposition while forming uniform droplet shape upon resin impregnation.
In this study, a hot plate type device was manufactured to observe the droplet forming process. We propose a method of making the droplet suitable for the equipment and set the temperature load condition. The equipment used was an oven, vacuum oven, and hot plate, and droplets were formed at the temperatures of 240, 270, 280, 300, and 320 [℃]. The microbond test was performed using the droplets thus formed. Interfacial shear strength and energy release rate were used for the analysis. Moreover, the droplet morphology was observed using a high magnification digital microscope.