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For automated fiber placement onto molds with complex surfaces, uneven compaction pressure distribution limits tows number in a single sequence and affects layup quality. Compaction roller has a direct influence on the pressure distribution, but the relationship between the two has not been widely explored. In this paper, the segmented compaction roller is used, and a theoretical model of compaction pressure distribution for layup onto general surfaces is established by analyzing the contact between the roller and prepreg layers, followed by experimental validation. Based on the model, single-point pressure uniformity and whole-path pressure uniformity are proposed to quantitatively evaluate the pressure distribution. Furthermore, pressure distribution and pressure uniformity of segmented roller and common roller are compared, as well as the influence of the two pressure distribution on layup quality. The results show that the established model can predict pressure distribution and provide a basis for analyzing layup defects, and segmented rollers apply evener compaction pressure and help to improve layup quality. [ABSTRACT FROM AUTHOR]

Automated fiber placement (AFP) combining with the autoclave curing process is the main manufacturing method for large-scale rotary composite parts. During the forming process, the mandrel plays an important role that affects the forming quality of the part directly. In this study, design and analysis of the mandrel structure for a composite S-shaped inlet are carried out. The preforming process of the rotary composite part using the AFP technique is introduced first. Then, design principles of the shaft are presented and applied to the shaft design for the mandrel of the S-shaped inlet, which then is transformed into an optimization problem. The internal penalty function method is adopted to solve this optimization problem in order to obtain the optimal axis position and axle diameter. Moreover, detailed structure design of the mandrel is proposed which takes the demolding into consideration, and the wall thickness is designed considering the total weight and the stiffness. The static analysis and modal analysis are also carried out by the finite element method to verify the feasibility of the proposed mandrel structure. [ABSTRACT FROM AUTHOR]

During automated fiber placement, insufficient compaction pressure leads to low bond strength between layers and may cause defects like bridging. The compaction roller contacts the prepreg and affects the pressure distribution directly. In this article, a model for analyzing the adaptability of rollers to molds is established. Then, compaction pressure distribution on prepreg tows is analyzed by finite element simulation and verified by pressure sensitive film experiment. Based on the simulation results, a calculation method of pressure uniformity is proposed. Moreover, the design parameters of the roller are optimized with an aim of improving pressure uniformity. The results show that the pressure uniformity can be improved significantly by design optimization of the roller, which indicated that higher bond quality between layers is achieved. [ABSTRACT FROM AUTHOR]

The resilient asynchronous dissipative control problem for Markov jump systems with sector-bounded nonlinearities in the discrete-time domain are examined in this study. The jumps between the system modes and controller modes are considered to be nonsynchronous. The mode transition of the controllers is governed by a nonstationary Markov chain, which can model the asynchronous jumps to different degrees that are also mode-dependent. The nonlinear functions are assumed to belong to sector sets with arbitrary boundaries. The sector boundaries can have positive and/or negative slopes, and therefore, we cover the most general case in our approach. Using the special structure of the system and by constructing a new multiple Lyapunov function, sufficient conditions regarding the existence of desired resilient asynchronous dissipative controllers are obtained in terms of linear matrix inequalities, which ensure the closed-loop system is stochastically stable and strictly dissipative. The designed controller can tolerate additive uncertainties in the controller gain matrix, which results from controller implementations. A numerical example is presented to show the effectiveness of the proposed theoretical results. [ABSTRACT FROM AUTHOR]

Large components such as wing sections should be aligned and positioned in a desired position prior to the final manufacturing or assembly, so a digital alignment and position device based on six degree of freedom parallel manipulator with several prismatic-prismatic-prismatic-spherical branches was designed and fabricated to meet the needs. The digital alignment and position device is an alignment device based on the parallel manipulator, and it is also a positioning and holding fixture for large components manufacturing or assembly. In order to effectively and efficiently select the supporting points of large component where the digital alignment and position device branch is connected with, the performance of the parallel manipulator and the fixture should be comprehensively analyzed at the same time. The global performance indices such as the dexterity index, the bearing capacity index, and the stiffness index are calculated based on the mechanism Jacobean matrix of the parallel manipulator, and the positioning stability index is calculated based on the position Jacobean matrix of the fixture. The results show that the global performance indices are not related to the pose, but the positioning stability index is; in addition, all indices rely on the originally selected supporting points and provide the basis for the effective selection of the supporting points for large component aligned and positioned by the digital alignment and position device, which is based on parallel manipulator with prismatic- prismatic-prismatic-spherical pairs. [ABSTRACT FROM AUTHOR]