Fiber Placement System Research Articles

Coordination control of the automated fiber placement system using photogrammetry-based leader–follower approach

The use of multiple robots in an automated fiber placement system (AFPS) makes it possible to manufacture composite structures with complex shapes. The robots in such system usually adopt independent trajectory planning and control methods. This makes the AFPS lack coordination, and rely heavily on the high-precision calibration of the system when completing complex fiber placement tasks. In this article, a novel photogrammetry-based leader–follower (PBLF) approach is proposed for a particular AFPS which consists of a serial manipulator and a parallel robot to improve its accuracy and coordination. The approach is composed of an offline trajectory planning module, a leader module, and a follower module. The trajectory planning algorithm in the offline trajectory planning module solves the problem of robot workspace constraints and mandrel occlusion in the fiber placement tasks for complex structure. Besides, a novel photogrammetry-based pose tracking method is proposed to make the follower robot track its desired relative trajectory with respect to the moving reference frame and keep the coordination of the two robots. The theoretical stability of the proposed approach is proved. The results of experiments indicate that the proposed approach can reduce the average mean absolute errors of the relative pose in position and orientation direction by 62.15% and 46.42%, respectively. While the corresponding average root mean square errors are reduced by 61.20% and 45.26%, respectively. Therefore, compared with Non-Coordination approach, the PBLF approach can effectively improve the coordination of the two robots.

Nonlinear Buckling and Postbuckling Analysis of Tow-Steered Composite Cylinders with Cutouts

The buckling and postbuckling behavior of two composite tow-steered shells with cutouts of different sizes is assessed using nonlinear finite element analysis and compared to experimental measurements. The cylindrical shells are manufactured using an automated fiber placement system, where the shells’ fiber orientation angles vary continuously around the shell circumference from on the crown and keel to on the sides. One shell features thickness variations due to tow overlaps that result from application of all 24 tows during each pass of the fiber placement system. The second shell uses the system’s tow drop/add capability to achieve a more uniform wall thickness without overlaps. Unreinforced cutouts of two different sizes—the first smaller cutout representing a passenger door on a commercial aircraft and the second larger cutout a cargo door—were machined into each of the two cylinders resulting in a total of four test cases. These cylinders were tested in axial compression and buckled elastically in previous work and are now analyzed using nonlinear finite element models to compare bifurcation buckling loads as well as the load–displacement response in the prebuckling and postbuckling regimes. For all four shells analyzed, the prebuckling stiffness, buckling load, and deformation mode sequence throughout the loading–unloading cycle is accurately reproduced by the models. In particular, the shells first buckle locally around the cutouts in a stable (supercritical) manner with only a slight decrease in axial stiffness, which occurs due to the favorable load redistribution facilitated by tow steering. The shells then buckle globally in an unstable (subcritical) manner with diamond-shaped buckles forming to the left and right (circumferential direction) of the cutouts. The buckling load of all shells with cutouts is at least 82% of the buckling load of the pristine shells without cutouts. Overall, the ability to sustain local buckling phenomena, and the relatively small reductions in global buckling load compared to pristine shells without cutouts, demonstrates the great potential of using tow steering to mitigate the adverse effects of cutouts in axially compressed shell structures.

Coordination Control of the Automated Fiber Placement System Using Vision-Based Leader-Follower Approach

Coordination Control of the Automated Fiber Placement System Using Vision-Based Leader-Follower Approach

Experimental investigations on natural fiber embedded additive manufacturing-based biodegradable structures for biomedical applications

PurposeThe purpose of this paper is to explore and investigate the mechanical as well as bacterial characteristics of chemically treated waste natural fiber inserted three-dimensional structures (NFi3DS) produced with fused filament deposition (FFD) for biomedical applications.Design/methodology/approachIn this work, a novel approach has been used for developing the customized porous structures particularly for scaffold applications. Initially, raw animal fibers were collected, and thereafter, the chemical treatment has been performed for making their wise utility in biomedical structures. For this purpose, silk fiber and sheep wool fibers were used as laminations, whereas polylactic acid was used as matrix material. A low-cost desktop time additive manufacturing setup was used for making the customized and porous parts by considering type of fiber, number of laminates, infill density and raster angle as input parameters.FindingsThe results obtained after using design of experimental technique highlighted that output characteristics (such as dimensional accuracy, hardness, three-point bending strength and bacterial test) are influenced by input parameters, as reported in the obtained signal/noise plots and analysis of variance. Optimum level of input parameters has also been found through Taguchi L9 orthogonal array, for single parametric optimization, and teaching learning-based algorithm and particle swarm optimization, for multiple parametric optimization. Overall, the results of the studies supported the use of embedded structures for scaffold-based biomedical applications.Research limitations/implicationsPresently, NFi3DS were produced by using the hand-lay-based manual approach that affected the uniform insert’s distribution and thickness. It is advised to use the automatic fiber placement system, synced with a three-dimensional printer, to achieve greater geometrical precision.Practical implicationsAs both natural fibers and polymer matrix used in this work are well established for their biological properties, hence the methodology explored in this work will help the practitioners/academicians in developing highly compatible scaffold structures.Social implicationsThe present work defines a new practice where the researchers can use natural fibers to reduce the cost associated with fabrication of customized scaffold prints.Originality/valueThe development of natural fiber embedded FFD-based structures is not yet explored for their feasibility in biomedical applications.

Semi-offline trajectory synchronized algorithm of the cooperative automated fiber placement system

Abstract This paper presents an innovative semi-offline trajectory synchronized algorithm for a cooperative AFP (Automated Fiber Placement) system which consists of a 6 degree-of-freedom (DOF) robot, a 6-RSS (Revolute-spherical-spherical) parallel robot, a spindle mounted on the platform to hold the mandrel. The cooperative AFP system is capable of manufacturing more complex composite components which pose high demand for trajectory planning than those by the current APF systems. However, for the cooperative AFP system, there might not be a feasible path for laying up the fiber due to the requirement of free from collisions and singularities in some cases. The semi-offline trajectory synchronized algorithm proposed in this paper can free the planned trajectory from strictly subjecting to the constraints and singularities by adding correction to pre-planned path online. Thus, the fiber can be laid up continuously without interruption. The correction is calculated based on the poses of the multi-robots detected by the photogrammetry sensor. When and how the offsets should be added to the parallel robot under the different circumstances are discussed in this paper. Experimental results demonstrate the successful avoidance of singularities and joint limits during manufacturing process.

Concept for Automated Production of CFRP-metal Hybrid Compounds Integrated in an Automated Fiber Placement Process

To solve the problem of load transmission into thin walled CFRP Structures, a new joining technology is being developed (Multi Layer Insert – MLI). It consists of multiple thin metal foils to distribute load optimally into every single CFRP layer. The placement process for the metal layers is integrated into an Automated Fiber Placement system. In this paper, a process sequence of MLI placement is presented containing the following steps: stockpiling of metal layers, separation, handling, positioning, lay up and fixation of metal layers during fiber placement. Moreover, the monitoring and control concept is discussed.

双头铺放轨迹后处理技术研究

为提升自动铺放装备工作效率并提高铺丝机工作的灵活度，对双机器人协同的类转体构件铺丝成型技术进行研究，提出了一个满足协调约束的轨迹预选机制。在确定了双机器人横向移动的配合方案后，以机器人平台可达空间的限制作为约束条件，通过夹角控制对铺丝轨迹进行配对编码并验证。同时得到完整模具的轨迹分配方案，将CAD软件生成的铺放信息转化成机器人角度的加工文件。文中模型证明所提方法满足大型类回转体构件铺放生产的工艺要求，大大提高了铺放效率。 In order to improve the rate and kinematic dexterity of automated fiber placement system tech-nology, a dual-robot collaborative placement of similar rotation component is studied, and the method of primary trajectory that fits the constraints of coordination is put forward. After deter-mination of the matching scheme for the longitudinal feed of the robot, the AFP trajectory is paired by the Angle control, under the constraint of the robot platform’s full reachable workspace. At the same time, the track distribution scheme of the complete mould is obtained, and the information generated by CAD software is transformed into the machining document of robot Angle. This paper proves that the proposed method meets the process requirements of the production of large class gyro member, which greatly improves the laying efficiency.

Automated Fiber Placement Head for Manufacturing of Innovative Aerospace Stiffening Structures

In the research project “High-performance Production of CFRP Structures” (HP CFK) a new automated fiber placement (AFP) system for laying thermoset CFRP (carbon fiber-reinforced plastic) slit tapes was developed. Its novel, modular designed laying head faces current industrial needs and challenges of prospective carbon light weight applications, e. g. future aerospace stiffening structures. Thus, its compaction unit is optimized for producing complex-curved structures. To allow approximating slopes on curved geometries, it consists of several height-adjustable rollers which, in addition, are each pressure controlled to enable an individual compacting pressure for the lay-up on materials with different compression strength (e. g. foams, metals). Furthermore, the design of the laying heads cutting unit aided the manufacturing of complex structures while being located as near as possible to the nip point to allow very short minimum placement paths. This paper introduces into the general design of the modular laying head as well as preliminary results of validation studies regarding several process limits.

APPLICATION OF LASER GENERATED ULTRASOUND FOR EVALUATION OF INTERNAL DEFECTS IN CARBON/PPS COMPOSITES

The aim of this study is to develop non-contact and real time inspection technique based on laser generated ultrasound for evaluating defects such as void, delamination in CFRP composite fabricated from recently developed 3-dimensional fiber placement system (FPS). Fiberized Nd ;YAG pulse laser is used to generate ultrasonic guided wave in the unidirectional Carbon/PPS specimen. The laser generation of narrowband ultrasound is achieved through a linear slit array. Receiving angle of air-coupled transducer is optimized by changing angle of it. The system has proven sensitive to defects in composite materials, and is well suited for on-line process control applications, with standoff distance for the transmitter and receiver, while retaining single-shot operation.

EXPERIMENTAL NON-CONTACT EVALUATION OF DELAMINATION IN CFRP COMPOSITE PLATES BY LASER GENERATION/AIR-COUPLED DETECTION ULTRASONIC SYSTEM

The objective of this research is to develop non-contact and real time inspection technique based on laser generated ultrasound for evaluating near-surface delamination in Carbon/Epoxy composite fabricated from automated fiber placement system. In this study, A hybrid laser generation/air-coupled detection ultrasonic system for detection and visualization of delamination in composite plates with simulated delamination of the area of 20 mm × 20 mm between the first and the second layer. Optical fiberized Nd :YAG pulse laser (532 nm, 32 mJ) with linear slit array is used to generate ultrasonic guided wave in unidirectional CFRP specimen (24 plies, 2.85 mm thickness). The characteristic of time domain waveform and frequency spectrum of guided wave is discussed. Two- dimensional images are obtained from these characteristics. The convergence of received signal using the pitch-catch and the scattering-reflection technique is discussed.

Laser-Generated Ultrasonic Technique for Inspecting Delamination in CFRP

For improving quality of a carbon fiber reinforced composite material (CFRP) by preventing defects such as delamination and void, it should be inspected in fabrication process. Novel non-contacting evaluation technique is required because the transducer should be contacted on the CFRP in conventional ultrasonic technique during the non-destructive evaluation and these conventional contact techniques can not be applied in a novel fiber placement system. For the non-destructive evaluation of delamination in CFRP, various methods for the generation and reception of laser-generated ultrasound are applied using piezoelectric transducer, air-coupled transducer, wavelet transform technique etc. The high frequency component of laser-generated guided wave received with piezoelectric sensor disappeared after propagating through delamination region. Air-coupled transducer was tried to be adopted in reception of laser-generated guided wave generated by using linear slit array in order to generate high frequency guided wave with a frequency of 1.1 MHz. Nevertheless, it was failed to receive high frequency guided wave in using air-coupled transducer and linear slit array. Transmitted laser-generated ultrasonic wave was received on back-wall and its frequency was analyzed to establish inspecting technique to detect delamination by non-contact ultrasonic method. In a frequency spectrum analysis, intensity ratio of low frequency and center frequency was approvable parameter to detect delamination.