Self-made tension machine was used to measure the evolution of recovery stress under different processing state for NiTiNb alloy. Then, SEM was used to investigate the microstructure evolution. The results show that the range of the highest recovery stress for forged NiTiNb alloy is between 210-215MPa. Otherwise, the recovery stress level of the samples enduring cold drawing and hot rolling is basically same, which all belong to the rage of 210-220MPa. After forging, the firstly precipitated TiNi phase particles become fine, only 5-8μm. The Nb tablets in eutectic microstructure, which originally contributed between TiNi phase particles, appear spheroidization.

In the process of composite placement, irregularity and asymmetry pressure fluctuation will affect the density and evenness of composite products, which lead to the inconsistency of interfacial strength and fiber volume fraction. The dynamic performance of placement pressure systems will be affected by external disturbance, mechanism friction and measurement noise. In this paper, an adaptive sliding mode control (ASMC) strategy based on disturbance observer (DOB) is proposed. The disturbance observer is introduced to estimate the equivalent disturbance torque, and the estimation error is compensated by the switching term of sliding mode control. The adaptive method is used to ensure that the switching gain is not overestimated, and then the Lyapunov function is used to verify the stability of the closed-loop control system. The experimental results and simulation analysis show that ASMC-DOB has high control accuracy and good robustness. At the same time, the designed algorithm can effectively reduce the void content of composite products.

Composite tape winding is an important forming process of composite materials, which can ensure good performance of composite products. Selection and control of key process parameters in the winding process have a great influence on the properties of products, such as void content and residual stress of products. Through experimental analysis, the residual stress and void content of the composite products are not the minimum when the prepreg winding process is carried out by using the empirical process parameters. To solve this multiobjective optimization problem, experiments were conducted using the Box–Behnken design. The multiobjective optimization problem is converted to a single-objective problem using grey relational analysis (GRA). Principal component analysis (PCA) is used to quantify the relative contributions of residual stress and void content. Regression analysis of grey relational grade (GRG) based on the experimental data was used to develop a second-order GRG prediction model. The winding process parameters were optimized with response surface methodology (RSM), and the winding experiments were carried out with these parameters. The experimental results show that the best combination of process parameters yields the best GRG results with better void content and residual stress.

Tension is a key processing parameter in the process of composite fiber tape winding. The fluctuation of tension will affect the accuracy of winding and the performance of winding products, such as stress uniformity, fatigue resistance, strength, compactness and resin content. In view of the winding tension is time-varying and the application of tension needs to be more accurate, a tension calculation model is established. Due to the influence of dynamic performance of tension control system by cogging torque, inverter dead zone, ring gear clearance, friction torque, parameter drift, and measurement noise, an adaptive sliding mode control (ASMC) based on extended state observer (ESO) is proposed. The stability of the closed-loop system is proven by Lyapunov theory, the system state variables is estimated by ESO, and the input dead-zone is compensated by the designed adaptive law. Simulation and experimental results show that ESO-based ASMC improves the robustness and dynamic response performance of the tension control system, and can effectively suppress the chattering of the sliding mode control system. The void content and residual stress of composite products have been improved obviously. INDEX TERMS Composites tape winding, dynamics modeling, ESO, ASMC, tension control.

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