Optimizing synthesis parameters of short carbon fiber reinforced polysulfonamide composites by using response surface methodology

Abstract

In this paper, the synthesis parameters of short carbon fiber reinforced polysulfonamide composites (SCF/PSA composites) were optimized. Box-Behnken design was applied to conduct the experiments. The influences of temperature, time and composition on mechanical strength of SCF/PSA composites were studied by response surface methodology and grey relational analysis. The results show the composition was the most influential factor and the optimal process parameters are as follows: 372.88 °C (temperature), 29.17 min (time), and 40 wt% (composition). The fracture surface morphology of compression and tension sections of the obtained composites was analyzed by Tungsten filament scanning electron microscopy (TF-SEM).

Introduction

The compressive and tensile strength is an important mechanical performance index of composite materials [1], [2], [3]. The reliability and service life of composite materials can be enhanced by improving the mechanical strength [4], [5], [6]. Aramid composites possess high fracture toughness but poor performance of anti-compression, while carbon fiber composites possess good anti-compression performance but poor fracture toughness. Carbon fiber/aramid fiber hybrid composites exploit the advantages of aramid composites and carbon fiber composites [7], [8], [9]. Due to the additional sulfonyl group structure in its main molecular chain, polysulfonamide fiber (PSA) has good heat resistance performance [10], [11], [12]. Polysulfonamide-based single polymer composites (PSA SPCs) can be manufactured from PSA [13]. Composite plates can be fabricated by mixing polysulfonamide fibers with carbon fibers. Response surface methodology is an effective method to model and analyze problems in which responses of interest are influenced by several quantifiable variables [14], [15], [16], [17], [18], [19], [20]. It has the characteristics of less number of experiments and good prediction. Design-Expert software can be used for designing experiment projects and processing the data by response surface methodology. However, there are few investigations on optimization of technological conditions of manufacturing SCF/PSA composites.

In this paper, SCF/PSA composites were fabricated by hot pressing process, using PSA as matrix and SCF as reinforced fibers. The Box-Behnken design (BBD) is a useful experimental design for response surface methodology based on three-level incomplete factorial designs. It helps to evaluate the effects, both individual and interactive of various variables for obtaining the best response. On the basis of three-level Box-Behnken design, response surface methodology (RSM) was employed to optimize three crucial preparation conditions. The results of experiments were analyzed by RSM with Design-Expert software. The mathematical regression model indicated the optimum technological conditions. Relevant experiments were employed to verify the optimum technological conditions. Furthermore, scanning electron microscopy (SEM) was carried out to study the fracture surface morphology after the compression and tension test.