(664f) Study of Recycled Carbon Fiber Length Distribution Measurement and the Effect to the Tensile Properties of Pulp-Molded CFRP

Carbon fiber reinforced plastics "CFRP" are performed as a promising solution of light weight demand for energy saving of transportations. Especially in aerospace industry one model of aircraft includes more than 50% weights of CFRP parts. The demands of CFRP are increasing due to the expansion of the application for automobiles, pressure vessels and the other markets. On the other hands, the poor recyclability of CFRP is one of big issue in environmentally and economically, motivates to work with recycle study in many institutes and companies. We had developed a CFRP recycle system through two stage thermal treatments including pyrolysis of plastics in inert conditions and oxidation of residue of carbonized plastics. The recycle carbon fiber obtained by the system indicates the physical properties of more than 80% tensile strength comparison to virgin carbon fiber and less than 1% residual carbonized plastics in a usual treatment condition. From the point of the recycle carbon fiber users view, it is important not only the tensile properties and impurities but also the fiber length and the distribution. In this report, we studied the methodology for a quality measurement of recycle carbon fiber length , and the effect to tensile properties of a pulp-molded CFRPs.

For the efficient measurement of fiber length, a commercially available optical scanner was introduced to the measurement procedure. To be homogenized the sample carbon fiber, the chopped carbon fiber was dispersed into water solution of a surfactant reagent. A part of the dispersion liquid was put into a pair of thin clear plastic film to prepare the scanning sample. The fiber length was measured by a personal computer with a software from the scanned image file. Both of virgin and recycle carbon fiber were applicable for the measurement procedure. The results of virgin carbon fiber were nearly equal to cut length, support the measurement value are reliable. In the case of recycle carbon fiber, the results were broader distribution including at least two different major group. One of major group value was equal to the cut length, the other group value was roughly 1.5 times greater than the cut length.

A pulp molding procedure was selected to convert the recycle carbon fiber to CFRP due to the easiness of machine preparation and the smallness experimental scale. A carbon paper was prepared as an intermediate product of CFRP. The carbon fiber was dispersed into a water solution of surfactant reagent and binding reagent, and it was filtered off by a metallic mesh to obtain the carbon paper. A polypropylene film was selected as a representative of thermoplastics, and an epoxy resin was selected as a representative of thermoset plastics.In both cases, the value of tensile test showed best result in CFRP using 10 mm carbon fibers.