Robotic Fibre Placement Research Articles

Optimization of thermoplastic composites process parameters based on robotic fiber placement

Optimization of thermoplastic composites process parameters based on robotic fiber placement

Online path correction under end point nonholonomic constraints – Implementation with visual sensing in robotic fiber placement

Online path correction under end point nonholonomic constraints – Implementation with visual sensing in robotic fiber placement

Effect of variable-angle trajectory structure on mechanical performance of CF/PEEK laminates made by robotic fiber placement

In comparison to the traditional fixed-angle trajectory, the variable-angle trajectory has a greater design space. However, it is a challenge to determine which common design curve structure is the most effective for improving mechanical performance. This work explores the effects of various design curves such as fixed-angle curve, linear curve, arc curve, sine curve, Bezier curve, and cubic polynomial curve trajectories on mechanical performance of laminates, including vibration modal performance and buckling performance. Genetic algorithm and improved NSGA-II algorithm are then used to optimize various curve structures. The results are confirmed utilizing thermoplastic Carbon Fiber (CF)/Polyether-Ether-Ketone (PEEK) laminates made by robotic fiber placement experiments. The relationship model between different mechanical performance and curve design variables is established. The optimization of variable-angle structure with mechanical properties as input variables is achieved. Meanwhile, a full-process angle-variable laying software platform from trajectory planning (CAD), trajectory optimization to manufacturing (CAM) is developed for facilitating the fiber placement application.

Evaluation of robotic fiber placement effect on process‐induced residual stresses using incremental hole‐drilling method

AbstractThe robotic fiber placement (RFP) process depends on continuous fusion bonding and solidifying of prepreg tows onto a substrate by subjecting them to a compression force and heat flux. However the advantages provided when using the RFP to fabricate the composite structures, it has adverse effects due to the induced residual stresses (RSs). The current work presents the effect of the RFP on the induced RSs in thermoset composites. RFP is utilized to fabricate specimens from carbon fiber reinforced polymers. Effects of placement speed, compression force, heating temperature, heating gas flowrate, and the location of the heat flux outlet nozzle are all included in the present study. A total of 69 flat panels are manufactured under different process conditions. Subsequently, the in‐depth RSs are measured using the incremental hole‐drilling method. Besides, the microstructures of the samples are also analyzed. The results show that the change in process parameters could significantly affect the induced RSs of the thermoset composites. Subjecting the samples to higher thermal and pressure loads would induce more RSs, which are attributed to the occurrence of partial curing during the manufacturing process along with the change in laminate geometry and porosity.

Optimization of process-induced residual stresses in automated manufacturing of thermoset composites

The present study investigates the effect of automated fiber placement process on the induced residual stresses in polymer-matrix composites. The robotic fiber placement is utilized to fabricate a total of 150 flat specimens. The specimens are then cured inside an autoclave. The incremental hole-drilling method is applied to estimate the maximum stresses induced in the laminates. Further, an optimization process is conducted based on the response surface method to minimize the generated stresses, while maintaining the highest production rate. A mathematical modeling of the relationship between the process parameters and the residual stresses is generated. The statistical analysis (ANOVA test) and sensitivity analysis are conducted to evaluate the generated model. The results show considerable effect on the stresses when changing the manufacturing process parameters due to the existence of in-situ curing and the change in material porosity. The optimization strategy could significantly decrease the stresses with maximizing the fabrication speed.

Study of the Automated Process-Induced Residual Stresses in Multi-Axis Laminates

The integrity of the composite structures is affected by the manufacturing conditions. Controlling the ply orientation during the manufacturing process plays an important role in defining the induced residual stresses inside the laminate. This work evaluates the generated residual stresses inside multi-axis laminates of carbon fiber reinforced polymers. The samples are manufactured using the robotic fiber placement technique. The residual stresses are measured through the incremental hole-drilling method. Finite element modeling is used to provide the calibration process of the strain measurements. Additionally, microstructure analyses have been performed to show the configuration of the manufactured samples. The effect of the laminate configurations and plies orientations are investigated and compared. The layers’ orientations have shown a considerable effect on the generated stresses.

On the Sensing and Calibration of Residual Stresses Measurements in the Incremental Hole-Drilling Method.

The current study presents three calibration approaches for the hole-drilling method (HDM). A total of 72 finite element models and 144 simulations were established to calibrate the measurements of the strain sensors. The first approach assumed the stresses acted on the boundaries of the drilled hole and thus analyzed the surrounding displacements field. The second analysis considered the loads on the outer surfaces of the specimen while measuring the strains’ differences between the model with and without the drilled hole. The third approach was more comprehensive as it considered the mechanical and thermal effects of the drilling operations. The proposed approaches were applied to two different materials (AISI 1045 and CFRP). The steel specimens were machined using a CNC lathe while the composite laminates were manufactured using the robotic fiber placement (RFP) process. Subsequently, the residual stresses (RSs) were measured using the HDM. The obtained data were compared with X-ray diffraction measurements for validation. The results showed better estimation of the RSs when utilizing the third approach and clear underestimation of the stresses using the second approach. A divergence in RSs values between the three approaches was also detected when measuring the stresses in the internal layers of the composite laminates.

Modal characteristics and manufacturing method of variable stiffness facesheets of sandwich plates made by robotic fiber placement

A variable stiffness (VS) structure of the grid panels is designed for solar wing sandwich plates on satellite. The vibration resistance performances of the VS plate, constant stiffness (CS) plate are evaluated. First, a novel modal analysis model is proposed to investigate the relationship between the fundamental frequency and fiber angles. The fiber direction of grid panel is optimized with the constant curvature arc curves. Then, the equivalent model and the boundary conditions of the sandwich plates under the actual working conditions are built. The modal fundamental frequencies of the VS plate are improved by 31.18% after the optimization. Furthermore, a five-segment method for trajectory planning is proposed. Finally, a variable stiffness grid panel made by robotic fiber placement is realized, which verifies the accuracy of the manufacturing method and simulations.

An approach for damage initiation and propagation in metal and carbon fiber hybrid composites manufactured by robotic fiber placement

Integrating the steel fibers into the carbon fiber-reinforced polymers (CFRP) structures provides a new material with unique properties, e.g., superior specific strength and stiffness, high damage tolerance, energy absorption and electrical functions. Manufacturing and investigating the steel/carbon fiber reinforced polymers (SCFRP) are an important attempt to monopolize their potential to contribute to the aviation industry. The current study presents a novel failure approach which can predict the damage initiation and propagation inside the metal/carbon hybrid composites. The analytical formulation is developed and implemented on the material through finite element analysis (FEA). Different SCFRP specimens are fabricated according to the required specifications using the robotic fiber placement (RFP) process. Subsequently, the failure behavior is analyzed by applying the tensile tests on the specimens. The analytical results are compared and validated by the experimental data. The proposed approach would enable predicting the failure behavior and the stiffness degradation of the generated material.

Thermal analysis of cylindrical molds using thermoplastic composite during robotic fiber placement

Thermoplastic composites have gradually become a hotspot due to its low manufacturing cost and good weld ability. In this study, to realize the placement of the thermoplastic composite material carbon fiber/polyether ether ketone (CF/PEEK), the consolidation roller of the existing thermoplastic composite placement head is optimized. The process simulation analysis of the thermoplastic composite material is carried out. A two-dimensional heat transfer model of the thermoplastic prepreg laying process is established in ANSYS. Transient thermal analysis is carried out using the life and death unit technology. The optimum machining parameters are obtained through analyzing the influence of mold temperature, laying speed, and heating temperature on the temperature field of the first layer in curved surface laying.

Design of Robotic Fiber Placement Machine and Process Optimization for Thermoplastic Composites

Design of Robotic Fiber Placement Machine and Process Optimization for Thermoplastic Composites

Developing a Trajectory Planning for Curved-Contoured Surfaces for Use by 8-DoF Workcell in Robotic Fibre Placement

The replacement rate of conventional material by composites is increasing. Possessing high specific strength and stiffness makes composites attractive to many applications. Different techniques are being utilized for composite placement processes. Robotic Fibre Placement (RFP) is introduced as a competing approach for composite fabrication. This approach can provide many advantages; e.g. low labor cost, high performance, quick and effective process. The current work proposes an 8-DoF system established for laying the composite material. This system composed of three main units includes a 6-DoF industrial robot and two mandrel tools with different configurations. A sensory-based feedback control system is developed to manage the placement process. The placement process can be performed on two different surfaces. The end-cap surface has been fabricated then the cylindrical surface. Different geometries of pressure vessels have been generated; e.g. Oxidizer tanks that can be used in many applications such as (Hybrid rockets).

Optimization of Process Parameters for Robotic Fibre Placement

Compared with labour-intensive and time-consuming processing of conventional fabrication methods, the robotic fiber placement process greatly improves the flexibility of the fiber placement process and allows for the construction of more complex structures. Based on the study of the placement process, the intimate contact process and healing process were analysed theoretically. The key process parameters for affecting the quality of the composite component were put forward:hot gas torch temperature, compaction force and laying velocity. In order to analyse the fabrication process for laying the cylindrical parts with 0-degree tow direction, the model of the process parameters coupling affected the interlaminar bond strength was established, according to the design of the response surface method. The reliability and validity of the model were verified by the analysis of variance. The optimal process parameters of fiber placement were obtained. The results show that the model is effective and the optimum peeling force of the laying products is 24.1 N under the optimum process parameters.

Multi-pass layup process for thermoplastic composites using robotic fiber placement

Abstract Robotic fiber placement is a promising technique to manufacture complex components for industry. Compaction pressure, hot gas torch temperature and laying velocity are the key molding factors for fiber placement process, and their optimal selection directly affects the product performance. Small compaction pressure, low gas temperature and fast laying velocity lead to incomplete interlaminar adhesion and high porosity. However, excessive compaction pressure, high gas temperature and slow laying velocity lead to excessive resin extrusion from the contact surface of the two layers, thus affecting the overall structural rigidity of the laminates. At the same time, due to the forming characteristics of fiber placement process, the compaction pressure has an impact on each underneath layer under the influence of heat transfer and laying velocity, which results in different interlaminar bonding strength between the different layers. This study aims at analyzing and optimizing the robotic fiber placement process parameters to obtain the composite laminate with the homogeneity of interlaminar bonding strength. Based on analyzing the heat transfer from current contact surface to each one underneath, the multi-pass compaction pressure from non-deformable roller affecting the underneath layers is investigated, and experiments are conducted to verify the optimizing method.

Ply Orientation-Driven Path Planning with Multi Reference Paths for Robotic Fiber Placement on Mesh Surface

This article reports an investigation of path planning with multi reference paths for robotic fiber placement (RFP) on open-contoured mesh surface. The new method considers the ply orientation information determined by loading characteristics, divides one surface into different parts according to the ply orientation information and then designs different initial reference paths in different parts. This article also proposes new up-layer design in order to make up for defects between parts and improve strength.

Pressure based approach for Automated Fiber Placement (AFP) with sensor based feedback loop and flexible component in the effector

New applications for robots include tasks that were performed by specialized machines such as polish, milling, placement of fibers, among others. The implementation using robots in these new applications has the inaccuracies problems due to the flexibilities within the robot arm or the tooling when external forces are applied. The industrial robot controller does not take into account the flexibilities and the external forces. This paper is an introduction to the work done to improve the precision in the robotic fiber placement, taking into account the deformation in the compaction roller.

Optimal Trajectories Generation in Robotic Fiber Placement Systems

The paper proposes a methodology for optimal trajectories generation in robotic fiber placement systems. A strategy to tune the parameters of the optimization algorithm at hand is also introduced. The presented technique transforms the original continuous problem into a discrete one where the time-optimal motions are generated by using dynamic programming. The developed strategy for the optimization algorithm tuning allows essentially reducing the computing time and obtaining trajectories satisfying industrial constraints. Feasibilities and advantages of the proposed methodology are confirmed by an application example.

Feasibility study of robotic fibre placement on intersecting multi-axial revolution surfaces

Abstract In this paper, the first steps towards using a robotic workcell for the automated fibre placement (AFP) manufacturing of Y-shaped tubes are proposed. The proposed workcell is constituted of a standard serial manipulator holding the fibre placement toolhead combined to a rotary table on which the part where the fibres must be laid out is attached. The investigations carried out in this work explore the feasibility of this setup and more precisely the path planning aspect. To this aim two novel path planning algorithms are presented generalizing the techniques proposed in the literature for open-contoured and cylindrical surfaces. In the first, the maximal geodesic curvature typically allowed in AFP is disregarded to generate continuous paths with a constant placement angle on the branches without any gaps or overlaps. Subsequently, a second algorithm, taking into account this curvature constraint, is presented. These algorithms were implemented in a software using the MATLAB™ suite. Finally, an algorithm to optimize the motion of the robotic system is presented and simulations are discussed.

AN ACCURATE PATH PLANNING ALGORITHM BASED ON TRIANGULAR MESHES IN ROBOTIC FIBRE PLACEMENT

Based on triangular meshes, an accurate path planning algorithm with the commonly used four laying angles in the robotic fibre placement (RFP) is proposed. The initial paths with different laying angles are firstly produced. Along certain directions, the offset curves are then obtained by a method of variable offset distances which are affected by the placement error and the number of fibre tows. The simulation results verify the effectiveness of this method.

An accurate approach to roller path generation for robotic fibre placement of free-form surface composites

Due to their high stiffness and strength, composites are widely used in the aerospace industry. To manufacture composites, especially composites of free-form surface structure, process of robotic fibre placement (RFP) is widely used in industry. However, due to the complex geometry of the free-form surface, it is quite challenging to generate accurate roller paths for placing fibre on the surface for high composites quality. To address this problem, this work proposes an accurate roller path planning method using the differential geometry. The roller paths can ensure the specified small gaps and overlaps between two tows for high composite quality. This approach is applied to several examples, and their results verify the validity of this approach. It has great potential to be adopted in industry.