Abstract:

Objective This study aims to enhance the efficiency and quality consistency of fiber winding and forming for carbon/carbon (C/C) composite preforms of a conical section, and to better meet the evolving demands on conical components, by developing a fiber-winding and forming robot system. Employing constant-tension control and precise trajectory planning, the system is expected to improve winding-path consistency and reduce defect rates, thereby providing a technical paradigm for the automated production of other C/C composite preforms.

Method A constant-tension winding head was designed to meet the demands of dry-fiber reinforcement winding, employing a spring-based tension mechanism to maintain consistent tension on the carbon fibers. In order to accommodate the uncapped ends of the conical mandrel and enable reliable fiber reversal and retention at the pin locations, a pin-plate tooling fixture was developed. Drawing on the mandrel's geometric characteristics and helical-winding theory, a mathematical model of the spiral winding trajectory was established, and MatLab-based simulations were conducted to numerically model and visually verify the winding paths. Additionally, a fiber-winding and forming robot system for conical C/C composite preforms was implemented, featuring a programmable logic controller (PLC) based control unit and seven-axis coordinated motion. Robot trajectory planning was performed using helical-winding theory in conjunction with an enhanced Denavit-Hartenberg parameter method.

Results After prototype commissioning, dry-fiber winding experiments were conducted on the C/C composite preforms of the conical section using constant-tension 12K PAN-based carbon fiber. Process parameters were set according to the constraint equations and mandrel geometric dimensions, where the mandrel rotational speed ω was π/4 rad/s, and the winding-head end-effector speed v was 20 mm/s. During each winding cycle, the first half-cycle comprised a 720° mandrel rotation while the end effector traversed the mandrel's generatrix at constant speed from the large end to the small end. In the second half-cycle, the mandrel rotated an additional 720° + Δθ (Δ θ is constant angular displacement) and the end effector returned from the small end to the large end. At cycle completion, the mandrel exhibited a constant angular displacement of Δθ=13.85°, establishing the precise spatial offset between successive layers via periodic angular superposition. A total of 26 cycles were required to achieve full coverage, at which point the cumulative mandrel rotation reached 360° and the carbon fibers densely and uniformly covered the conical surface. Throughout each cycle, the fibers were stably guided by the rotating mandrel and end effector in both winding directions, with uniform deposition and no fiber overlap. Comparison of the actual winding trajectories to the simulated profiles showed excellent agreement. The planned path enabled smooth, collision-free operations between the winding head and mandrel, with no fiber bridging or pin interference observed. During early cycles, the fibers maintained intimate contact with the mandrel surface without slippage, and at the end of each cycle, fibers adhered equally well to both the mandrel and underlying layers, without noticeable slip. A protractor was adopted to sample the winding angles at the large end, mid-section, and small end of the conical mandrel over five winding cycles, and the mean relative error was calculated. The mean relative errors at the large end, mid-section, and small end were 0.62%, 0.91%, and 1.71%, respectively. The largest deviation occurred at the small end, primarily due to the introduction of the tuning coefficient ξ and inherent measurement uncertainties. All errors remained below 2%, which satisfies the allowable process tolerance.

Conclusion This study solves the problems on low efficiency, high labor intensity, and poor consistency of manual winding for the C/C composite preforms of the conical section by developing an automated fiber-winding and forming robot system. At its core, a PLC-based controller coordinates a constant-tension carbon-fiber winding head as the end-effector and a servo-driven rotating mandrel as an external auxiliary axis, thereby ensuring stable fiber tension control and synchronized mandrel rotation. Drawing on helical-winding theory and trajectory simulation, a pin-plate tooling-assisted winding scheme was devised. Furthermore, precise path planning based on an enhanced D-H parameter method was performed to guarantee smooth robot motion along the prescribed trajectories. Experimental results demonstrate good agreement between theoretical and actual winding paths, uniform fiber placement without overlap or slippage, confirming the feasibility and engineering value of the proposed pin-plate-assisted conical winding approach and robot system.

Key words: conical section, carbon/carbon composite preform, industrial robot, dry fiber reinforcement winding, needle disk fixture