Effects of Scrap Size on Mechanical Properties of Recycled Carbon Fiber Reinforced Plastics

Abstract

As increasing the demand and using of carbon fiber reinforced plastics (CFRPs) in recent years, the necessity of recycling CFRPs has been also increased. To recycle CFRPs, retrieving carbon fibers is mainly used, and for this, pyrolysis and solvolysis are mainly used. These methods, however, consume enormous energy and have even high global warming potential [1]. In this study, mechanical recycling was suggested to recycle end-of-life CFRPs rather than retrieving carbon fibers for more effective recycling. The material used in this research was carbon fiber/low melting-poly(aryletherketone) (CF/LM-PAEK) which has high thermal properties and its melting temperature is 305℃. Trimmed or end-of-life CFRPs were shredded the scraps were sieved with different mesh sizes of sieves to be normalized their sizes. To find out the effect of sieving process, particle size distribution (PSD) was analyzed by image analysis and statistical analysis. Compression molding was conducted with different weight fraction of different sizes of scraps by using heating press. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) were conducted to compare thermal properties of each step which are raw material (unidirectional tape), scraps and reCFRPs. Cross section of reCFRPs was observed by optical microscope for evaluating impregnation and stacking quality of the composites. To measure mechanical properties, tensile testing, flexural testing, drop weight impact testing were conducted. After that, fracture mechanisms of the reCFRPs were investigated. Parameters of compression molding process which are pressure, temperature, time and cooling rate was optimized using results of thermal analysis. PSD was used for investigating the effects on mechanical properties because PSD followed Weibull distribution and it is known that PSD can replace fiber length distribution (FLD) of composites [2]. Small size of scraps had also important role of decreasing variation even larger scraps affected to strength. Through cross section observation, small scraps filled empty spaces between large scraps to bond each other, which leads to have higher reliability. In this study, it was found that scrap size affects to mechanical properties of recycled carbon fiber reinforced plastics. Reference [1] F. Meng. SAMPE Europe Conference 2018 Southampton [2] G. A. Vincent. Composites Part B (2019)