Kiyoshi Kemmochi

Research in Recycling Technology of Fiber Reinforced Polymers for Reduction of Environmental Load: Optimum Decomposition Conditions of Carbon Fiber Reinforced Polymers in the Purpose of Fiber Reuse

The objective of the present study is to investigate the effect of pyrolysis time and temperature on the mechanical properties of recycled carbon fiber, based on tensile strength measurements, determining the optimum decomposition conditions for carbon fiber-reinforced polymers (CFRPs) by superheated steam. In this research, CFRPs were efficiently depolymerized and reinforced fibers were separated from resin by superheated steam. Tensile strength of fibrous recyclates was measured and compared to that of virgin fiber. Although tensile strength of recycled fibers were litter lower than that of virgin fiber, under some conditions tensile strength of recycled fibers were close to that of virgin fiber. With pyrolysis, some char residue from the polymer remains on the fibers and degrees of char on the recycled fibers were closely examined by scanning electron microscopy.

Impact Force when Fabric Inflates at High Speed

Occupant protection systems for automobiles are currently highly publicized. An airbag inflating at high speed impacts an occupant with great force. Airbag safety relies on its construction with primarily woven fabrics. We have referred to a typical pressure-time history of an airbag and developed a device to measure impact load when the fabric airbag inflates at high speed. When interior pressure in the airbag increased, impact load increased. Also, the impact load on a body increased as the distance between the body and airbag decreased. The impact force of an airbag inflating at high speed was simulated by a non-linear finite element method (FEM) combined with an incremental method, where the sample was modeled by a thin elastic shell. An experiment was conducted to verify the theory and this calculation method. Good agreement was obtained between the theoretical and experimental values for two types of fabric sample. This demonstrated that the mathematical technique developed here can satisfactorily predict the impact force when an airbag inflates at high speed and that the impact force depends appreciably on the mechanical properties of fabrics.

Research on FRP Composite Structures with Self-Healing Function - Effect of Filler on FRP Interlaminar Fracture Toughness

In reacent years, studies on reducing the diameter of microcapsules for practical application to self-healing FRP have been conducted. This study clarifies how filler grain diameter and strength and filler volume fraction affect the interlaminar fracture toughness of FRP. The reinforcement material used in this experiment was carbon fiber fabric sheets. Acrylic particles were used as filler; the mechanical properties were similar to those of microcapsules of self-healing FRP. The filler volume fraction was confirmed to affect the interlaminar fracture toughness. The grain diameters of the hollow particles were smaller, and the Youngs modulus of the filler is larger, confirming that the interlaminar fracture toughness increased. High rigidity and small-grain diameter microcapsules are considered to be appropriate microcapsules (enclosing repair agents) for self-healing of CFRP.

Improvement of the Bending Characteristics of Thin FRP Cylinders by Imitating Nodes of Bamboo

Thin cylinders of fiber-reinforced plastic (FRP) material are used in large quantities as a kind of structural material for robot arms, airplanes and aerospace applications because of their light weight and high strength. In order to improve the mechanical properties of these cylinders, this study applied the VaRTM method to develop a biomimetic design of a thin cylinder with nodes that imitate a bamboo structure. The effects of inserted nodes on the bending properties of a thin FRP cylinder were examined by the four-point bending test. It is evident that the flexural rigidity and bending buckling load were increased; the validity of the node has also been confirmed.

Electric Capacity Characteristic of Nanofiber/Vulcanized Rubber

Rubber material generally behaves as an electrical insulator, and vapor grown carbon fiber (VGCF) has excellent electrical conductivity. In our study, we mixed carbon nanofiber (VGCF) into styrene–butadiene rubber and investigated the relationship between strain and the electric capacitance of vulcanized rubber filled with VGCF, of which the hardness was not changed. The electric capacitance of the rubber filled with VGCF increased with VGCF content but decreased with increasing tensile strain. We confirmed that the change rate of electric capacitance is related to the VGCF content of the fillers. In order to investigate the relationship between strain and electric capacitance of rubber with VGCF, it is feasible to apply rubber composites filled with VGCF as a strain sensor.

Shock Absorbing Characteristic of Laminated FRP Cylinder

Development for introducing new material technology and new structural design technology in ski poles has been conducted in recent years. Although the CFRP pole is light, the impact is strong. The shock absorbing characteristic of the FRP is important for the application of robot arm and ski pole etc. In this work. the theoretical method was suggested about shock absorbing characteristic. An impact test apparatus was developed for verify the theory and this calculation method. The agreement obtained between the theoretical and the experimental values of seven types of laminated composite cylinders, these being unidirectional (0°, 90°) plies, cross-plies (±15°, ±30°, ±45°, ±60°, ±75°) plies. It shows that the mathematical technique developed here is satisfactory for predicting the shock absorbing values (maximum impact load) of laminated composite cylinders. Shock absorbing characteristic of laminated composite cylinder varies with fiber orientation angle. Effect of EL is large in near at 0°, and effect of GLT is large in near at 45°about maximum impact load.

Improving bending characteristics of FRP sandwich structures with reinforcement webs

Sandwich-structure materials consist of a high-strength skin material and a lightweight core material. The advantages of sandwich structures are known to include excellent mechanical properties and low weight. Sandwich structures are lightweight because of their lightweight core; meanwhile, the skin structure provides mechanical strength and bears bending stress. Carbon-fiber-reinforced plastic (CFRP) is a high-specific-strength and high-specific-rigidity material. In recent years, CFRP sandwich structures have been used in aerospace applications due to their lightweight properties. However, soft-core members such as plastic foam materials have low rigidity and therefore may not exhibit adequate function as a sandwich structure. Webs can make up for the lack of rigidity of soft core members. Consequently, sandwich structures with reinforcement webs offer higher strength than sandwich structures without reinforcement webs. This study focused on reinforcement webs suitable for use in CFRP sandwich structures by evaluating the bending characteristics of CFRP sandwich structures with reinforcement webs. Experimental results demonstrated that CFRP sandwich structures with reinforcement webs had improved bending strength. The effects of the spacing interval of reinforcement webs and the number of layers of carbon fiber fabric on the bending characteristics of CFRP sandwich structures were also examined. Finally, an optimal condition model was created for CFRP sandwich structures with reinforcement webs.

Effects of fiber orientation angles of fiber-reinforced plastic on sand solid particle erosion behaviors

Solid particle erosion in industrial applications has been a serious problem in many engineering fields. Earlier studies on fiber-reinforced plastic (FRP) composites were mainly focusing on the erosive wear behavior at several different impact angles. However, the effect of fiber orientation on FRP composites has not been thoroughly investigated. Since fiber orientation is one of the important factors in which causing erosive wear damages to FRP composites, in order to understand the virtue of this problem, it is important to investigate the effect of fiber orientation at different impact angles. In this research, the effect of fiber orientation of unidirectional fiber-reinforced plastic composites on erosive wear behavior was studied. Sandblasting-type erosion tests were conducted on the FRP composites with fiber orientation ranging at three impact angles to clarify the relation between fiber orientation and erosive wear behavior. The Dyneema fiber (ductile material) and the carbon fiber (brittle material) were used for the reinforcement fiber in FRP. From the result, it is confirmed that CFRP composites with higher fiber orientation angle erode faster than the composites with lower fiber orientation angle. But the erosion characteristic of DFRP was almost the same regardless of the fiber orientation angle. The damaged surfaces of the FRP composites were then analyzed using scanning electron microscopy and the possible erosion wear mechanisms were investigated.

The Mechanical Property of Recycled Fiber Reinforced Polymer Composites by Superheated Steam

Fiber Reinforced Polymer (FRP) composites are used in many applications for their excellent strength-to-weight ratio. These properties are significant barriers for achieving the 3R concept (Recycle, Reuse, and Reduce). Inverse manufacturing is a recent technology that produces new materials and industrial goods from FRP waste based on life-cycle assessment (LCA), and it is expected to help solve the problems of 3R associated with FRP [1-. However, no effective recycling system of FRP has been established because of the cross-linked structure of thermosetting resin matrix and inorganic reinforcement fibers. To investigate the possibility of recycling and reusing both matrix and reinforcements, a project of preventing environmental deterioration was performed. In this study, a new decomposition method for recycling FRP waste by superheated steam was developed. Separation of the resin matrix and reinforcement fiber from the FRP was attempted, the FRP recycled from the separated fibers was remolded; this is called R-FRP.

Measurement and evaluation methods for damage of fibers from dry sand erosion in a hot environment

Bag filters composed of fibrous components are widely used to clean exhaust gas. It is reported that filter damage during dust collection involves erosion wear caused by particle collision. Thus, it is necessary to determine the life of bag filters in a hot environment and to clarify the erosion mechanism of fibrous materials. Experiments and evaluation methods were developed to investigate the erosion of fiber at high temperatures. The experiments involved reproducing the erosion of fibrous materials in various temperatures. Analysis of the relationship between the erosion damage rate of a specimen and the total kinetic energy of particles before colliding indicates the erosion resistance of fibrous materials at various temperatures. Using the suggested damage energy curve, we can evaluate the erosion wear characteristics of fiber under different experimental conditions.