Thickness design of polyester-ramie/epoxy nonwoven composite applied on pipeline rehabilitation

The thickness of tubular polyester-ramie/epoxy nonwoven composites has a certain influence on the flow capacity and strength of the lining material after pipeline rehabilitation. Therefore, the calculation formulas of thickness and overcurrent capability were established based on manning equation and the design criterion of composite pipe. The formula for calculating the strength was also established. The response surface method was used to optimize the preparation process of polyester-ramie nonwovens. Based on the single factor, according to the Box-Behnken test design principle, the three factors of hybrid ratio, fiber web quantification and needle density were selected according to the regression analysis equation. To determine the influencing factors of each process, the thickness and strength of the polyester-ramie nonwovens were used as the response surface and the contour map. The optimum process conditions for the preparation of polyester-ramie nonwovens are as follows:the hybrid ratio is 0.8, the fiber web quantification is 600 g/m² and the needle density is 300 needle/cm². Under the process, the polyester-ramie nonwovens have a thickness of 4.14 mm, a longitudinal tensile strength of 2.81 MPa, and a transverse tensile strength of 1.72 MPa, which is close to the theoretical value, indicating that the response surface method has practical value. Combined with polyester-ramie/epoxy nonwoven composites, the thickness and strength were used to verify rationality of the calculation formulas such as thickness, overcurrent capability and strength. It is found that the strength of the thinner polyester-ramie/epoxy nonwoven composites can meet the pressure requirements of the lining for repairing the drainage or sewage pipeline under the premise of the over-flow capability of the pipeline after repair.