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

2021 ◽  
pp. 114042
Author(s):  
Jiahai Zhang ◽  
Zhenyu Han ◽  
Yuhua Liu ◽  
Shouzheng Sun
Keyword(s):  
Variable Stiffness ◽  
Sandwich Plates ◽  
Manufacturing Method ◽  
Modal Characteristics ◽  
Fiber Placement

scholarly journals Defect Characteristics and Online Detection Techniques During Manufacturing of FRPs Using Automated Fiber Placement: A Review

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1337 ◽  
Author(s):  
Shouzheng Sun ◽  
Zhenyu Han ◽  
Hongya Fu ◽  
Hongyu Jin ◽  
Jaspreet Singh Dhupia ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Large Scale ◽  
Variable Stiffness ◽  
Future Research ◽  
Online Detection ◽  
Manufacturing Defects ◽  
Manufacturing Method ◽  
Detection Techniques ◽  
Fiber Placement ◽  
Automated Fiber Placement

Automated fiber placement (AFP) is an advanced manufacturing method for composites, which is especially suitable for large-scale composite components. However, some manufacturing defects inevitably appear in the AFP process, which can affect the mechanical properties of composites. This work aims to investigate the recent works on manufacturing defects and their online detection techniques during the AFP process. The main content focuses on the position defect in conventional and variable stiffness laminates, the relationship between the defects and the mechanical properties, defect control methods, the modeling method for a void defect, and online detection techniques. Following that, the contributions and limitations of the current studies are discussed. Finally, the prospects of future research concerning theoretical and practical engineering applications are pointed out.

scholarly journals Optimization of variable stiffness composites with embedded defects induced by Automated Fiber Placement

2014 ◽  
Vol 107 ◽  
pp. 160-166 ◽  
Author(s):  
Mahdi Arian Nik ◽  
Kazem Fayazbakhsh ◽  
Damiano Pasini ◽  
Larry Lessard
Keyword(s):  
Variable Stiffness ◽  
Fiber Placement ◽  
Automated Fiber Placement

Size-dependent behavior of laminates with curvilinear fibers made by automated fiber placement

2015 ◽  
Vol 22 (2) ◽  
pp. 157-163 ◽  
Author(s):  
Mahdi Arian Nik ◽  
Larry Lessard ◽  
Damiano Pasini
Keyword(s):  
Variable Stiffness ◽  
Buckling Load ◽  
Fiber Placement ◽  
Plate Size ◽  
Load Increase ◽  
Automated Fiber Placement ◽  
Fiber Path ◽  
Turning Radius ◽  
Curvilinear Fibers ◽  
Minimum Turning Radius

AbstractVariable stiffness laminates can be manufactured using curvilinear fiber paths. A curvilinear fiber path is generally defined based on the plate size and has a curvature that is dependent on the plate size. In practice, however, the fiber path must satisfy manufacturing constraints, such as the minimum turning radius imposed by the automated fiber placement machine, thereby limiting the possible amount of fiber steering. In this work, we studied the effect of the plate size on the structural properties of a plate manufactured with curvilinear fibers. We considered four plate sizes, which were designed by a constant curvature fiber path. We optimized the plates for both maximum buckling load and in-plane stiffness. The results showed that the in-plane stiffness of the plate was not controlled by the plate size, whereas the buckling load was highly affected by the curvature of the fiber path. Hence, the potential of a buckling load increase reduced for plate sizes smaller than the minimum turning radius. In addition, for a given maximum curvature of the fiber path, the influence of a complex layup on the buckling load was marginal.

Three-dimensional solutions for free vibration of variable stiffness laminated sandwich plates with curvilinear fibers

2018 ◽  
Vol 22 (3) ◽  
pp. 896-925 ◽  
Author(s):  
A Houmat
Keyword(s):  
Free Vibration ◽  
Three Dimensional ◽  
Orientation Angle ◽  
Variable Stiffness ◽  
P Element ◽  
Skin Thickness ◽  
Sandwich Plates ◽  
Aspect Ratios ◽  
Transverse Shearing ◽  
Curvilinear Fibers

This paper is concerned with the free vibration of variable stiffness laminated sandwich plates with curvilinear fibers. The three-dimensional elasticity theory and the p-version of the finite element method are adopted for the analysis. The skin is composed of one or more plies with curvilinear fibers. The fiber path orientation angle in a ply is assumed to vary linearly with the x coordinate. The plies may be stacked symmetrically or anti-symmetrically with respect to the middle surface of the plate. Each layer is modeled as one brick p-element. The principle of virtual displacements is used to derive the element stiffness and mass matrices. The generalized displacements at vertices, edges, and faces shared by elements are matched to ensure inter-element compatibility. Since no solutions are available for the free vibration of such variable stiffness laminated sandwich plates, the validity, convergence, and accuracy of the present three-dimensional method are established by comparing with existing three-dimensional frequencies for constant stiffness laminated sandwich plates with rectilinear fibers. The study reveals that inter-layer modal bending stresses are discontinuous; modal transverse shearing stresses are constant in the core; the sign of modal transverse shearing stresses can change through the thickness of the skin; and the shape of modal cross-sectional warping is influenced by the mode number and stacking sequence of plies. Three-dimensional frequencies are presented for different fiber orientation angles, boundary conditions, aspect ratios, thickness ratios, core/skin thickness ratios, and stacking sequences of plies. The accurate results presented here will serve as a benchmark for future investigations.

scholarly journals Optimizing Variable-Axial Fiber-Reinforced Composite Laminates: The Direct Fiber Path Optimization Concept

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Lars Bittrich ◽  
Axel Spickenheuer ◽  
José Humberto S. Almeida ◽  
Sascha Müller ◽  
Lothar Kroll ◽  
...  
Keyword(s):  
Composite Laminates ◽  
Variable Stiffness ◽  
Tensile Specimen ◽  
Path Optimization ◽  
Fiber Reinforced ◽  
Simulation And Optimization ◽  
Fiber Placement ◽  
Fiber Path ◽  
Curvilinear Fibers ◽  
Novel Concept

The concept of aligning reinforcing fibers in arbitrary directions offers a new perception of exploiting the anisotropic characteristic of the carbon fiber-reinforced polymer (CFRP) composites. Complementary to the design concept of multiaxial composites, a laminate reinforced with curvilinear fibers is called variable-axial (also known as variable stiffness and variable angle tow). The Tailored Fiber Placement (TFP) technology is well capable of manufacturing textile preforming with a variable-axial fiber design by using adapted embroidery machines. This work introduces a novel concept for simulation and optimization of curvilinear fiber-reinforced composites, where the novelty relies on the local optimization of both fiber angle and intrinsic thickness build-up concomitantly. This framework is called Direct Fiber Path Optimization (DFPO). Besides the description of DFPO, its capabilities are exemplified by optimizing a CFRP open-hole tensile specimen. Key results show a clear improvement compared to the current often used approach of applying principal stress trajectories for a variable-axial reinforcement pattern.

Design and Manufacturing of Variable Angle Tow Laminate

2016 ◽  
Vol 674 ◽  
pp. 59-64 ◽  
Author(s):  
Anti Haavajõe ◽  
Madis Mikola ◽  
Meelis Pohlak
Keyword(s):  
Surface Roughness ◽  
Composite Structure ◽  
Variable Stiffness ◽  
Pneumatic Cylinder ◽  
Fiber Reinforced ◽  
Strength Performance ◽  
Analysis And Design ◽  
Fiber Placement ◽  
Variable Angle ◽  
Compaction Force

Variable angle tow (VAT) laminates have shown enhanced stiffness/strength performance compared to conventional straight fiber laminates. Employment of VAT allows utilizing variable stiffness design of composite structure, thus it widens the design possibilities. As a result, composite structure with improved mechanical characteristics can be manufactured. The main aims of the current study are to give an overview on methods and algorithms used for analysis and design of VAT laminates, and to develop technology and equipment for manufacturing laminate with improved structural performance. In order to improve the accuracy of the compaction process, a set of experiments were carried out using a simple testing device. For measuring the compaction force, a pneumatic cylinder, pressure regulator and digital manometer were used. The temperature of the consolidation area and the heat distribution were screened with the thermal camera. Infrared heater was used as a heating source. Material used in the experiment was carbon fiber reinforced polyamide.Findings show that in addition to the main parameters – the compaction force and temperature, there are many minor factors, such as the compaction wheel diameter, material and surface roughness of the compaction roller, the material and surface roughness of the mold and the pretension in the laminating tape and also the laminating speed, all influence the quality of the final product.Key words: Advanced Fiber Placement Technology, Automated Fiber Placement, Automated Tape Laying, Fiber Reinforced Composites, Laminates

scholarly journals Overlap-Stiffened Panels for Optimized Buckling Performance Under Minimum Steering Radius Constraints

2020 ◽  
Author(s):  
Raphael Ummels ◽  
Saullo G. P. Castro
Keyword(s):  
Design Method ◽  
Variable Stiffness ◽  
Radius Of Curvature ◽  
Stiffened Panels ◽  
Fiber Placement ◽  
Design Variables ◽  
Automated Fiber Placement ◽  
Circular Fiber ◽  
Straight Fiber ◽  
Radius Constraint

Recent research on variable stiffness laminates have shown both numerically and experimentally that further improvement on the buckling behaviour is possible by incorporating overlaps that result in variable thickness profiles, with the thickness non-linearly coupled with the local steering angle. We present the concept of overlap-stiffened panels, developing a design method that allows for incorporating higher-stiffness regions into individual plies of a variable-angle tow (VAT) laminate, taking advantage of the non-linear coupling between the tow steering angles and the local thickness. The proposed method naturally copes with minimum steering radius constraints of different manufacturing processes, and the present study considers two tow steering processes: automated fiber placement (AFP) and continuous tow shearing (CTS). The minimum radius constraint is satisfied by connecting two transition regions of thickness specified on each ply by means of circular fiber tow arcs, of which the radius of curvature always exceed the minimum manufacturing constraint. Each individual ply exploring the overlap-stiffened design is described using 5 design variables. Laminates made up of these overlap-stiffened plies are optimized for a maximum volume-normalized buckling performance under bi-axial compression, measured through FEM, by a genetic algorithm and benchmarked against a straight fiber panel optimized for the same load case. The conclusion can be drawn that both AFP and CTS overlap-stiffened VAT panels can at least achieve the double of the volume-normalized buckling performance of an optimized straight fiber panel, demonstrating the potential of the proposed design method.

scholarly journals Foam core composite sandwich plates and shells with variable stiffness: Effect of the curvilinear fiber path on the modal response

2017 ◽  
Vol 21 (1) ◽  
pp. 320-365 ◽  
Author(s):  
Francesco Tornabene ◽  
Nicholas Fantuzzi ◽  
Michele Bacciocchi
Keyword(s):  
Kinematic Model ◽  
Free Vibration Analysis ◽  
Variable Stiffness ◽  
Sandwich Plates ◽  
Composite Sandwich ◽  
Doubly Curved Shells ◽  
Present Solution ◽  
Reinforcing Fibers ◽  
Doubly Curved ◽  
Composite Sandwich Plates

This paper presents the free vibration analysis of composite sandwich plates and doubly curved shells with variable stiffness. The reinforcing fibers are located in the external skins of the sandwich structures according to curved paths. These curvilinear paths are described by a general expression that combines power-law, sinusoidal, exponential, Gaussian and ellipse-shaped functions. As a consequence, the reinforcing fibers are placed in these orthotropic layers in an arbitrary manner, in order to achieve the desired mechanical properties. The effect of this variable fiber orientation on the natural frequencies is investigated by means of several parametric studies. As far as the structural theory is concerned, an equivalent single layer approach based on the well-known Carrera Unified Formulation is employed. The Murakami’s function is added to the kinematic model to capture the zig-zag effect, when the soft-core effect is significant. Thus, several higher order shear deformation theories are taken into account in a unified manner. The differential geometry is employed to describe the reference surface of doubly curved shells and panels, which are characterized by variable radii of curvature. The numerical solution is obtained using the generalized differential quadrature method, due to its accuracy and stability features. The present solution is compared with the results available in the literature or obtained by finite element commercial codes.

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