A CLT based constitutive model to predict distortions and residual stresses in semi-crystalline thermoplastic composites

2021 ◽  
pp. 002199832110120
Author(s):  
Dante Krivtzoff De’ Grandis ◽  
Maurício Vicente Donadon ◽  
Alfredo Rocha de Faria ◽  
Rita de Cássia Mendonça Sales-Contini
Keyword(s):  
Constitutive Model ◽  
Residual Stresses ◽  
Aerospace Industry ◽  
Design Guidelines ◽  
Thermoplastic Composites ◽  
Final Part ◽  
Cooling History ◽  
Part Quality ◽  
Laminate Theory ◽  
Residual Strains

This paper describes a classical laminate theory-based constitutive model for portraying thermoplastic composites’ mechanical properties and the development of residual stresses during consolidation. The extended Hillier model is applied to describe the material’s crystallisation and as such is able to provide final part quality as a function of the process cooling history while taking into account the first and second crystallisation mechanisms occurring concurrently. With the developed model, a parametric study was performed taking into account layups that are commonly used in the aerospace industry, where general design guidelines are suggested. Some of the advantages of using cross-ply and quasi-isotropic laminates became clear as no shear residual stresses were predicted for those laminates. However, highly anysotropic laminates may also offer structural advantages. Numerical simulations indicate that the crystallisation residual strains can be, although smaller than thermal residual strains, relevant to final part quality. The combination of both effects may result in high residual stresses at ply level which in turn can compromise the ultimate strength of the laminates and make it difficult to attain the desired part’s geometrical tolerances.

scholarly journals Residual stresses developed in thermoplastic composites during laser-assisted tape laying

2021 ◽  
Author(s):  
Anna Maria El Bayssari ◽  
Frédéric Jacquemin ◽  
Mael Péron ◽  
Anaïs Barasinski ◽  
Fédérica Daghia ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Filament Winding ◽  
Thermoplastic Composites ◽  
Whole Process ◽  
Curvature Variation ◽  
Laminate Theory ◽  
Winding Machine ◽  
Laminate Thickness

The main focus of the study is the determination of residual stresses developed in thermoplastic composites during tape placement. An experimental characterization of the residual stresses is carried out and based on the measurement of the curvature variation with temperature for unsymmetrical laminates. The tested plates are made of APC-2 and processed on the SPIDE-TP, a filament winding machine based in Cetim, France. A thermo-mechanical model based on the modified laminate theory is used in this work. Heat transfer and crystallization are taken into account in the model, allowing the description of the evolution of the mechanical properties of the composite during the whole process. The model is able to predict the residual stresses present at the end of the process. The results showed stress gradients through the thickness of the laminates where the transverse residual stresses can reach up to 20 MPa. In addition, the results showed that increasing the mandrel temperature reduces the crystallization and thermal gradients in the laminate thickness.

scholarly journals A STRUCTURED APPROACH TO REDUCE DESIGN ITERATIONS IN ADDITIVE MANUFACTURING

2021 ◽  
Vol 1 ◽  
pp. 231-240
Author(s):  
Laura Wirths ◽  
Matthias Bleckmann ◽  
Kristin Paetzold
Keyword(s):  
Additive Manufacturing ◽  
Spare Parts ◽  
Design Guidelines ◽  
Final Part ◽  
Layer By Layer ◽  
Powder Bed ◽  
Batch Sizes ◽  
Manufacturing Technologies ◽  
Structured Approach ◽  
Design Freedom

AbstractAdditive Manufacturing technologies are based on a layer-by-layer build-up. This offers the possibility to design complex geometries or to integrate functionalities in the part. Nevertheless, limitations given by the manufacturing process apply to the geometric design freedom. These limitations are often unknown due to a lack of knowledge of the cause-effect relationships of the process. Currently, this leads to many iterations until the final part fulfils its functionality. Particularly for small batch sizes, producing the part at the first attempt is very important. In this study, a structured approach to reduce the design iterations is presented. Therefore, the cause-effect relationships are systematically established and analysed in detail. Based on this knowledge, design guidelines can be derived. These guidelines consider process limitations and help to reduce the iterations for the final part production. In order to illustrate the approach, the spare parts production via laser powder bed fusion is used as an example.

Measurement of Residual Stresses in Linear Friction Welded In-Service Inconel 718 Superalloy

2016 ◽  
Vol 879 ◽  
pp. 1800-1806 ◽  
Author(s):  
M. Smith ◽  
L. Bichler ◽  
D. Sediako
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Base Material ◽  
Peak Stress ◽  
Weld Interface ◽  
Aerospace Alloys ◽  
Aero Engine ◽  
Linear Friction ◽  
Inconel 718 Superalloy ◽  
Residual Strains

Measurement of residual strains by neutron diffraction of linear friction welded Inconel® 718 (IN 718) superalloy acquired from a mid-service aero-engine disk was undertaken in this study. Residual strain and stress throughout the various weld regions including the heat affected zone (HAZ), thermomechanical affected zone (TMAZ) and dynamically recrystallized zone (DRX) were characterized. The residual stresses were observed to increase from the base material to the weld interface, with a peak stress at the weld interface in all orthogonal directions. The trends for residual stress across the weld are in agreement with other work published in literature for solid state welding of aerospace alloys, where high residual stresses were commonly reported at the weld interface.

Residual Stresses in Overlapping Friction Taper Stud Welds

2010 ◽  
Vol 652 ◽  
pp. 111-115 ◽  
Author(s):  
D.G. Hattingh ◽  
Axel Steuwer ◽  
M. Neil James ◽  
I.N. Wedderburn
Keyword(s):  
Solid State ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Creep Damage ◽  
Local Damage ◽  
Planar Defects ◽  
Repair Technique ◽  
Damage Repair ◽  
Stud Welding ◽  
Residual Strains

This paper presents microstructural, hardness and residual strain information for solid-state welds in creep-resistant Cr-Mo steel, made using the new local damage repair technique offered by friction taper stud welding (FTSW). The technique is suitable for making single welds to repair, for example, localised creep damage but can also be extended to deal with planar defects through the use of overlapping welds. Neutron diffraction was used to measure residual strains at a number of positions along a series of 5 overlapping FTS welds.

Variation of Residual Stresses in Drawn Copper Tubes

2008 ◽  
Vol 571-572 ◽  
pp. 21-26 ◽  
Author(s):  
Adele Carradò ◽  
D. Duriez ◽  
Laurent Barrallier ◽  
Sebastian Brück ◽  
Agnès Fabre ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Residual Stresses ◽  
Material Flow ◽  
Cold Drawing ◽  
Axisymmetric Deformation ◽  
Tube Length ◽  
Inhomogeneous Deformation ◽  
Drawing Process ◽  
Process Step ◽  
Residual Strains

Seamless tubes are used for many applications, e.g. in heating, transport gases and fluids, evaporators as well as medical use and as intermediate products for hydroforming and various mechanical applications, where the final dimensions normally are given by some cold drawing steps. The first process step – piercing of the billet, for example by extrusion or 3-roll-milling - typically results in ovality and eccentricity in the tube causing non-symmetric material flow during the cold drawing process, i.e. inhomogeneous deformation. Because of this non-axisymmetric deformation and of deviations over tube length caused by moving tools, this process step generates residual stresses. To understand the interconnections between the geometrical changes in the tubes and the residual stresses, the residual strains in a copper tube had been measured by neutron diffraction.

MODELING AND SIMULATION OF THE CURING PROCESS OF EPOXY RESINS AND FIBER COMPOSITES

2021 ◽  
Author(s):  
ANASTASIA MULIANA
Keyword(s):  
Constitutive Model ◽  
Residual Stresses ◽  
Elastic Moduli ◽  
Processing Parameters ◽  
Fiber Composites ◽  
Curing Process ◽  
Reinforced Composites ◽  
Micromechanics Model ◽  
Epoxy Curing ◽  
Exothermic Process

This study discusses simulations of the curing process in epoxy and fiberreinforced polymer composites incorporating changes in the thermal and mechanical properties of epoxy during curing at various temperatures. A coupled constitutive model that includes an exothermic process from the cross-linking, heat conduction across the specimen and deformations of the specimen from the thermal expansion and shrinkage effects is formulated. The model is used to capture the curing process in the epoxy resin. The coupled constitutive model is then integrated into a micromechanics model of fiber-reinforced composites and used to study the influence of epoxy curing on the formation of residual stresses in the composites. Furthermore, the micromechanics model is also used to predict the macroscopic properties, i.e., elastic moduli, of the cured composites. The model can then be used to understand the influence of processing parameters, i.e., temperatures and pressure, on the formation of residual stresses and their consequences on the overall properties of cured composites.

The Meed for Experimentally Determined X-ray Elastic Constants

1976 ◽  
Vol 20 ◽  
pp. 355-367 ◽  
Author(s):  
R. H. Marion ◽  
J. B. Cohen
Keyword(s):  
Residual Stresses ◽  
Elastic Constants ◽  
X Ray Diffraction ◽  
X Ray ◽  
Residual Strains ◽  
Entire Specimen ◽  
Representative Material

In order to convert residual strains measured by x-ray diffraction techniques into residual stresses, appropriate x-ray elastic constants have to be measured. Since these x-ray elastic constants may depend on the metallurgical state, deformation, and entire specimen history, errors in stress values may result if the constants are not measured for representative material states. In the present work, it is shown that in same cases these errors may be large.

Temperature Dependence of Residual Stresses and Stress Relaxation in Blanket Films of Various Thicknesses

1994 ◽  
Vol 356 ◽  
Author(s):  
A. P. Clarke ◽  
G. Langelaan ◽  
S. Saimoto
Keyword(s):  
Residual Stress ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Back Stress ◽  
Temperature Cycling ◽  
Misfit Dislocations ◽  
X Rays ◽  
Heating Rates ◽  
Residual Strains ◽  
Continuous Temperature

AbstractA rapid method to measure residual strains using x-rays during continuous temperature ramping has been developed whereby resolution of ±5xl0-5 can be attained with 2θ scans of about one minute using low index reflections. The method was used to make residual stress measurements during temperature cycling at heating rates of 2 to 15°C/min with interrupted stress relaxations at 235°C and 130°C on pure Al blanket films of 0.24μm, 0.58μm and 1.01 μm thicknesses. The results are consistent with the notion that surface sources are activated by the back stress of misfit dislocations.

Inhomogeneous Deformation Examples and Applications of Light Activated Shape Memory Polymers

2012 ◽  
Author(s):  
Jaskirat S. Sodhi ◽  
Swapnil Moon ◽  
I. Joga Rao
Keyword(s):  
Constitutive Model ◽  
Shape Memory ◽  
Boundary Value Problems ◽  
Boundary Value ◽  
Aerospace Industry ◽  
Shape Memory Polymers ◽  
Inhomogeneous Deformation ◽  
The Past ◽  
Innovative Materials ◽  
Biomedical Industry

Light Activated Shape Memory Polymers (LASMP) are recently developed innovative materials defined by their capacity to store a deformed (temporary) shape and recover an original (parent) shape. This change in shape and the return to original shape is achieved by exposing the polymer to light at different wavelengths. These unique properties have led to the use of LASMP’s in a wide variety of applications. These SMP’s have a great potential in the biomedical industry as well as the aerospace industry. In the past, the authors have introduced a constitutive model to model the mechanics of these LASMP [1] and used it to solve a few cases of boundary value problems of interest. In this paper, the developed model is used to solve some other inhomogeneous deformation boundary value problems.

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