scholarly journals Irreversible and Repeatable Shape Transformation of Additively Manufactured Annular Composite Structures

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1383
Author(s):  
Bona Goo ◽  
Jong-Bong Kim ◽  
Dong-Gyu Ahn ◽  
Keun Park
Keyword(s):  
Composite Structures ◽  
Memory Function ◽  
Dimensional Accuracy ◽  
Transformation Method ◽  
Manufacturing Cost ◽  
Thermal Stimulus ◽  
4D Printing ◽  
Shape Transformation ◽  
Shape Transformations ◽  
Accuracy And Repeatability

Four-dimensional (4D) printing is a unique application of additive manufacturing (AM) which enables additional shape transformations over time. Although 4D printing is an interesting and attractive phenomenon, it still faces several challenges before it can be used for practical applications: (i) the manufacturing cost should be competitive, and (ii) the shape transformations must have high dimensional accuracy and repeatability. In this study, an irreversible and repeatable thermoresponsive shape transformation method was developed using a material extrusion type AM process and a plain thermoplastic polymer (ABS) without a shape-memory function. Various types of annular discs were additively manufactured using printing paths programmed along a circular direction, and additional heat treatment was conducted as a thermal stimulus. The programmed circumferential anisotropy led to a unique 2D-to-3D shape transformation in response to the thermal stimulus. To obtain more predictable and repeatable shape transformation, the thermal stimulus was applied while using a geometric constraint. The relevant dimensional accuracy and repeatability of the constrained and unconstrained thermal deformations were compared. The proposed shape transformation method was further applied to AM and to the in situ assembly of a composite frame–membrane structure, where a functional membrane was integrated into a curved 3D frame without any additional assembly procedure.

Shape transformations of Pt nanocrystals enclosed with high-index facets and low-index facets

CrystEngComm ◽  
2021 ◽  
Vol 23 (38) ◽  
pp. 6655-6660
Author(s):  
Chi Xiao ◽  
Na Tian ◽  
Wei-Ze Li ◽  
Xi-Ming Qu ◽  
Jia-Huan Du ◽  
...  
Keyword(s):  
Potential Method ◽  
High Index ◽  
Shape Transformation ◽  
Square Wave ◽  
Wave Potential ◽  
Shape Transformations ◽  
Pt Nanocrystals

Shape transformation between high-index faceted Pt nanocrystals and low-index faceted ones have been achieved by an electrochemical square-wave potential method.

Additive manufacturing-enabled shape transformations via FFF 4D printing

2018 ◽  
Vol 33 (24) ◽  
pp. 4362-4376 ◽  
Author(s):  
Abishera Ravichandra Rajkumar ◽  
Kumar Shanmugam
Keyword(s):  
Additive Manufacturing ◽  
4D Printing ◽  
Shape Transformations ◽  
Image Position

Abstract

Resin Infusion of Triaxially Braided Preforms With Through-the-Thickness Reinforcement

2001 ◽  
Author(s):  
Jay R. Sayre ◽  
Alfred C. Loos
Keyword(s):  
Composite Structures ◽  
High Performance ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Element Model ◽  
Manufacturing Cost ◽  
Fiber Volume ◽  
Resin Infusion ◽  
Infiltration Process ◽  
High Fiber

Abstract Vacuum assisted resin transfer molding (VARTM) has shown potential to significantly reduce the manufacturing cost of high-performance aerospace composite structures. In this investigation, high fiber volume fraction, triaxially braided preforms with through-the-thickness stitching were successfully resin infiltrated by the VARTM process. The preforms, resin infiltrated with three different resin systems, produced cured composites that were fully wet-out and void free. A three-dimensional finite element model was used to simulation resin infusion into the preforms. The predicted flow patterns agreed well with the flow pattern observed during the infiltration process. The total infiltration times calculated using the model compared well with the measured times.

Tolerance Analysis and Synthesis for Composite Assemblies of Resin Transfer Molded Components

Manufacturing ◽  
2003 ◽  
Author(s):  
Chensong Dong ◽  
Chuck Zhang ◽  
Zhiyong Liang ◽  
Ben Wang
Keyword(s):  
Composite Structures ◽  
Dimensional Accuracy ◽  
Tolerance Analysis ◽  
Process Models ◽  
Design Parameters ◽  
Element Analysis ◽  
Control Dimension ◽  
And Control ◽  
Prediction Approach ◽  
Variation Model

With the increasing demand for composite products to be affordable, net-shaped and efficiently assembled, tight dimension tolerance is critical. Due to lack of accurate process models, dimension analysis and control for resin transfer molding (RTM) processes are often performed using trial-and-error approaches based on engineers’ experiences or previous production data. Such approaches are limited to specific geometry and materials and often fail to achieve the required dimensional accuracy in the final products. This paper presents an innovative dimension variation prediction approach. First a dimension variation model was developed based on process simulation, the classical laminate theory (CLT) and finite element analysis (FEA). The FEA-based dimension variation model was validated against experimental data. The deformations of common features in typical composite structures were analyzed using the FEA-based dimension variation model. Design parameters were identified and the regression-based dimension variation model was developed. The model provides a fast, practical and proactive tool to predict and control dimension variations in RTM processes. The structural tree method (STM) is presented for design optimization and tolerance analysis/synthesis of composite assemblies.

Performance Evaluation of Notched Biaxial Braided Composites

2004 ◽  
Author(s):  
Jitendra S. Tate ◽  
Ajit D. Kelkar ◽  
Ronnie Bolick
Keyword(s):  
Composite Structures ◽  
Low Cost ◽  
Impact Resistance ◽  
High Volume ◽  
Manufacturing Cost ◽  
Braided Composites ◽  
Static Tensile Loading ◽  
New Process ◽  
Static Tensile ◽  
Potential Benefits

Braided composites have good properties in mutually orthogonal directions, more balanced properties than traditional tape laminates, and have potentially better fatigue and impact resistance due to the interlacing. Another benefit is reduced manufacturing cost by reducing part count. Because of these potential benefits braided composites are being considered for various applications ranging from primary/secondary structures for aerospace structures [1]. These material systems are gaining popularity, in particular for the small business jets, where FAA requires take off weights of 12,500 lb. or less. The new process, Vacuum Assisted Resin Transfer Molding (VARTM), is low cost, affordable and suitable for high volume manufacturing environment. Recently the aircraft industry has been successful in manufacturing wing flaps, using carbon fiber braids and epoxy resin and the VARTM process. To utilize these VARTM manufactured braided materials to the fullest advantage (and hence to avoid underutilization), it is necessary to understand their behavior under different loading and environmental conditions. This will reduce uncertainty and hence reduce the factor of safety in the design. It is well known fact that the strength of the composite structure reduces because of discontinuities and abrupt change in the cross-section. Accurate knowledge of strength and failure mechanism of notched and unnotched composites is very important for design of composite structures. This research addresses the behavior of notched braided composites under static tensile loading.

SHAPE TRANSFORMATION MODELS AND THEIR APPLICATIONS IN PATTERN RECOGNITION

1990 ◽  
Vol 04 (01) ◽  
pp. 65-94 ◽  
Author(s):  
Z.C. LI ◽  
Y.Y. TANG ◽  
T.D. BUI ◽  
C.Y. SUEN
Keyword(s):  
Pattern Recognition ◽  
Chinese Characters ◽  
Computer Algorithms ◽  
Transformation Models ◽  
Shape Transformation ◽  
Geometric Properties ◽  
Shape Transformations ◽  
Computer Recognition ◽  
Theoretical Analyses

This paper presents linear and bilinear shape transformations including basic transformations, analyzes their geometric properties, and provides computer algorithms. The shape transformations can be used to simplify the recognition of Roman letters, Chinese characters and other pictorial patterns by normalizing their shapes to the standard forms. Important theoretical analyses have been performed to illustrate that the linear and bilinear transformations are applicable to computer recognition of digitized patterns. A number of pictorial examples have been computed to confirm the analyses and conclusions made.

scholarly journals 4D Printing Self-Morphing Structures

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1353 ◽  
Author(s):  
Mahdi Bodaghi ◽  
Reza Noroozi ◽  
Ali Zolfagharian ◽  
Mohamad Fotouhi ◽  
Saeed Norouzi
Keyword(s):  
Composite Structures ◽  
Fused Deposition Modeling ◽  
Functionally Graded ◽  
Complex Structures ◽  
Mechanical Behaviors ◽  
4D Printing ◽  
Digital Tool ◽  
Fused Deposition ◽  
Straightforward Method ◽  
Deposition Modeling

The main objective of this paper is to introduce complex structures with self-bending/morphing/rolling features fabricated by 4D printing technology, and replicate their thermo-mechanical behaviors using a simple computational tool. Fused deposition modeling (FDM) is implemented to fabricate adaptive composite structures with performance-driven functionality built directly into materials. Structural primitives with self-bending 1D-to-2D features are first developed by functionally graded 4D printing. They are then employed as actuation elements to design complex structures that show 2D-to-3D shape-shifting by self-bending/morphing. The effects of printing speed on the self-bending/morphing characteristics are investigated in detail. Thermo-mechanical behaviors of the 4D-printed structures are simulated by introducing a straightforward method into the commercial finite element (FE) software package of Abaqus that is much simpler than writing a user-defined material subroutine or an in-house FE code. The high accuracy of the proposed method is verified by a comparison study with experiments and numerical results obtained from an in-house FE solution. Finally, the developed digital tool is implemented to engineer several practical self-morphing/rolling structures.

Innovative Building Forms Determined by Orthotropic Properties of Folded Sheets Transformed Into Roof Shells

2020 ◽  
Vol 61 (2) ◽  
pp. 111-124
Author(s):  
Aleksandra Prokopska ◽  
Jacek Abramczyk
Keyword(s):  
Computational Models ◽  
High Sensitivity ◽  
Free Form ◽  
Shape Transformation ◽  
Steel Sheets ◽  
Shape Transformations ◽  
Thin Walled ◽  
Orthotropic Properties ◽  
Roof Shells ◽  
Qualitative And Quantitative Characteristics

Qualitative and quantitative characteristics of geometrical and mechanical changes of nominally plane steel sheets folded in one direction, caused by big elastic shape transformations were invented on the basis of the authors' tests, analyzes and computational models of thin-walled folded sheets transformed into shell shapes. Both geometrical and mechanical changes produce significant restrictions in using sheets for shell forms. The deliberate transformations and sheets' characteristics are required to obtain attractive and innovative forms of roof shells and their consistent structures as well as entire buildings. The search for effective solutions related to free forms of buildings and shape transformations of sheets especially in the fields of: shape transformation, effort and stabilization of their walls is necessary due to the high sensitivity of thin-walled open profiles to boundary conditions and loads. A method for shaping such free form buildings that effectively exploit specific orthotropic properties of the transformed sheeting is presented.

An experimental approach to manufacturability assessment of microfluidic devices produced by stereolithography

2020 ◽  
Vol 234 (24) ◽  
pp. 4905-4916
Author(s):  
Mattia Mele ◽  
Giampaolo Campana
Keyword(s):  
Regression Models ◽  
Low Cost ◽  
Dimensional Accuracy ◽  
Binary Logistic Regression ◽  
Polymeric Materials ◽  
Microfluidic Devices ◽  
Combined Effect ◽  
Manufacturing Cost ◽  
Linear Regression Models ◽  
Logistic Regression Models

Lab-on-a-Chips integrate a variety of laboratory functions and embed microchannels for small fluid volume handling. These devices are used in medicine, chemistry, and biotechnology applications but a large diffusion is limited due to the manufacturing cost of traditional processes. Additive Manufacturing offers affordable alternatives for the production of microfluidic devices, because the fabrication of embedded micrometric channels is enabled. Stereolithography gained particular attention due to the low cost of both available machines and suitable polymeric materials to be processed. The main restriction to the adoption of this technique comes from the obtainable dimensional accuracy that depends not only on design, but also on process set-up. Firstly, the paper analyses theoretically the physics of stereolithographic processes and focuses on main phenomena related to microchannel manufacturing. Then, specific experimental activities are designed to investigate the combined effect of design and process parameters on the achievable dimensional accuracy of embedded microchannels manufactured through a commercial desktop stereolithography apparatus. In particular, the combined effect of channel nominal dimensions, build orientations and the layer thickness on the obtainable accuracy is examined by referring to a benchmark geometry. The collated experimental data showed that a number of combinations are successful. Besides, the experimental activity revealed that appropriate combinations of design, build orientation and manufacturing parameters can overcome the dimensional limitations reported in previous studies. Both binary logistic regression models to predict the manufacturability of microchannels and linear regression models to estimate the achievable accuracy for those geometries that can be produced successfully are developed.

Sign in / Sign up

Export Citation Format

Share Document