Analysis of fiber stresses during high-tension winding molding of thermoplastic composites

High-tension winding technology provides thermoplastic composite parts that can resist high centrifugal forces by applying radial compressive stresses. Based on the thick-walled cylinder theory of elastic mechanics and the principle of small deformation, mathematical model of the fiber stress distribution and radial compressive stress on the mandrel surface under the combined effects of tension and temperature field during the composite winding and molding process is established. A method for applying tensile forces to balance thermal stress is proposed. Results show that the thermal stress can reduce the relaxation effect of the inner layers of fibers during the winding process. With the increase in the number of winding layers under the three methods of tension application, namely, constant, constant torque, and taper tension, the fiber circumferential stress decreases layer by layer from the inside to the outside, while the radial compressive stress on the mandrel surface gradually increases. The equal stress tension provides the maximum radial compressive stress. When the stress per unit width of the fibers in each layer of the composite is 266.67 MPa, the radial compressive stress on the mandrel surface after 30 layers of winding is 15.52 MPa. The finite element simulation results show that the maximum error of composite circumferential stress and theoretical calculation is 6.7%, and the maximum error of radial compressive stress on the mandrel surface is 0.4%. These results verify the reliability of the mathematical model in this paper and provide theoretical support for the tension design in the high-tensile winding molding process of thermoplastic composite fibers.