Design of Experiments-Based Optimization of Manufacturing Parameters to Improve the Properties of GFRPP Composite Rebars

This paper presents a novel thermoplastic composite rebar pultrusion and winding technique aimed at addressing the challenges associated with fiber content in rebar and its bonding performance with concrete. The proposed technology employs thermoplastic pre-impregnated tape with a high fiber content, enabling the creation of embedded rib structures. The Taguchi optimization methods are applied in this study to experimentally investigate the effects of various parameters on the properties of glass fiber-reinforced polypropylene (GFRPP) composite rebars. The parameters examined in the experiment include pulling speed, heating temperature and mouth-dies taper, which were incorporated into an experimental design utilizing an L9 orthogonal array. Signal-to-noise (S/N) ratios and analysis of variance (ANOVA) were employed to identify the optimal values for strength and the manufacturing parameters of the GFRPP rebars. The ANOVA results indicated that the contribution rates of mouth-dies taper to the tensile strength, transverse shear strength, and flexural strength of GFRPP rebars were 70.4%, 67.6%, and 58.7%, respectively. From this analysis, the maximum tensile strength, flexural strength, transverse shear strength and short-beam shear strength of GFRPP rebars manufactured under the optimal parameters were determined to be 915.7, 580.4, 154.9, and 22.5 MPa, respectively. Notably, Fiber Bragg grating (FBG) technology was utilized for on line monitoring of temperature and strain during the manufacturing of GFRPP rebar. Finally, images obtained via SEM were analyzed using image processing technology to calculate the void area and count, allowing for an examination of the relationship between voids and the manufacturing parameters.