Polymer composite frame has been frequently used in the main structural body of vehicles in aerospace, automotive, etc., applications. Manufacturing of complex curved composite frame suffer from the lack of accurate and optimum method of winding process that lead to preparation of uniform fiber arrangement in critical location of the curved frame. This article deals with the fabrication of high-quality polymer composite frame through an optimal winding of textile fibers onto a non-bearing core frame using a fiber-processing head and an industrial robot. The number of winding layers of fibers and their winding angles are determined based on the operational load on the composite structure. Ensuring the correct winding angles and thus also the homogeneity of fibers in each winding layer can be achieved by using an industrial robot and by definition of its suitable off-line trajectory for the production cycle. Determination of an optimal off-line trajectory of the end-effector of a robot (robot-end-effector (REE)) is important especially in the case of complicated 3D shaped frames. The authors developed their own calculation procedure to determine the optimal REE trajectory in the composite manufacturing process. A mathematical model of the winding process, matrix calculus (particularly matrices of rotations and translations) and an optimization differential evolution algorithm are used during calculation of the optimal REE trajectory. Polymer composites with greater resistance to failure damage (especially against physical destruction) can be produced using the above mentioned procedure. The procedure was successfully tested in an experimental composite laboratory. Two practical examples of optimal trajectory calculation are included in the article. The described optimization algorithm of REE trajectory is completely independent of the industrial robot type and robot software tools used and can also be used in other composite manufacturing technologies.

The extraordinary features of fibrous composites enable advanced industries to design composite structures with superior performance compared to traditional structures. Composite frame structures have been designed frequently as components of mechanical systems to resist lateral and gravity loads. The manufacturing of high-quality composite frames depends primarily on the accurate fiber winding on frames with different pro-files and curved shapes. The optimal fiber winding process on a nonbearing composite frame with a circular cross-section is described in previous works by the same authors. As an extension to that, this study focuses on the manufacturing of straight-line composite frames with different profile radii at multiple locations. Such production procedure allows continuous winding of fibers gradually on individual parts of the frame and generally with different angles of fiber winding. The winding procedure is performed using fiber-processing head and industrial robot. The procedure for calculating the distance of the winding plane of fibers on the frame from the guide-line of the fiber-processing head is targeted. This distance depends on the required angle of fiber winding, the radius of the frame, and the geometric parameters of the fiber-processing head. The coordination of the speed of winding the fibers on the frame and the speed of the passage of the frame through the winding head is also considered. Determining the correct distance of winding the fibers from the corresponding guide-line of fiber-processing head and right coordination of the winding speed and the speed of passage of the frame through the fiber-processing head ensure compliance of the required angles of fiber windings on the frame and homogeneity of winding fibers, which are the two of the most important prerequisites for producing a quality composite frame. The derived theory is well verified on a practical experimental example.

Light-weight fibers reinforced polymer (FRP) composite frames are essential parts of vehicles body in the aerospace and automotive industries. Composite frames are often designed in complex curved 3D geometry through the dry winding process. The winding process of homogeneously wound-up layers of fibers without overlapping and gaps is the main challenge in the fabrication of frames with consistent thickness and acceptable quality. In this study, an industrial robot and winding head are set with a novel optimum process to wind the dry fiber with the specified angles on the frame, to fabricate it with minimum overlapping and local commulation of fibers, yet without gaps. Mathematical models and algorithms are developed to determine the optimal number of simultaneously wounds rovings of fibers in a given layer. In addition, this study addresses the optimum dry winding of curved parts of frames that form a torus geometry. It is shown that the combination of layers of rovings wound successively on the frame at angles of 45°, 90° (i.e. the rovings are laid along with the frame), and −45°, is the most used variant of winding that provides the composite frame with higher strength. Results indicated that an optimal selection of the number and width of the rovings minimizes the overlap of the wound rovings, which saves up to 20% of the utilized fibers. The derived theory is verified on practical tests and experiments, which confirms the development of new suitable procedures to improve the fabrication of FRP composite frames.

Currently, traditional materials are very often replaced by composite materials in many industrial areas. The advantages of these materials consist mainly in their lightweight, high strength and flexibility, corrosion resistance and a long lif...

The differential evolution is a popular and efficient way to solve complicated optimization tasks with many variables and constraints. In this article we study the ability of the differential evolution algorithms to attain the global minimum of the cost function. We demonstrate that although often declared as a global optimizer the classic differential evolution algorithm does not guarantee the convergence to the global minimum. To improve this weakness we design a modification of the classic differential evolution algorithm to enrich the diversity of its populations. This modification limits the premature convergence to local minima and ensures the asymptotic global convergence. We tested the modified algorithm in numerical experiments and compared the efficiency in finding the global minimum for the classic and modified algorithm. The modified algorithm is significantly more efficient with respect to the global convergence than the classic algorithm.

The article is focused on the problem of generating a uniform temperature field on the inner surface of shell metal moulds. Such moulds are used e.g. in the automotive industry for artificial leather production. To produce artificial leather with uniform surface structure and colour shade the temperature on the inner surface of the mould has to be as homogeneous as possible. The heating of the mould is realized by infrared heaters located above the outer mould surface. The conceived mathematical model allows us to optimize the locations of infrared heaters over the mould, so that approximately uniform heat radiation intensity is generated. A version of differential evolution algorithm programmed in Matlab development environment was created by the authors for the optimization process. For temperate calculations software system ANSYS was used. A practical example of optimization of heaters locations and calculation of the temperature of the mould is included at the end of the article.