 | Kappel E. Process distortions in composite manufacturing: Diss. … Dr.-Ing. / Deutsches Zentrum für Luft- und Raumfahrt, Institut für Faserverbundleichtbau und Adaptronik. - Köln: DLR, Bibliotheks- und Informationswesen, 2013. - xv, 191 p.: ill. - (Forschungsbericht; 2013-03). - Bibliogr.: p.181-187. - ISSN 1434-8454
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List of Acronyms ............................................... ix
List of Symbols ................................................ xi
Introduction .................................................... 1
1 The Problem's Topicality and Relevance Nowadays .............. 3
1.1 The Problem's Topicality ................................ 3
1.2 Goals of the Thesis ..................................... 4
1.3 Phenomena Spring-in and Warpage: A Definition ........... 7
1.4 Relevance and Consequences of Manufacturing
Deformations ........................................... 12
1.5 Strategies to Counteract Process Distortions ........... 16
1.6 Review of the Literature ............................... 18
1.7 Essence and Cognitions of the Review ................... 24
2 Research Objectives and Thesis Outline ...................... 33
3 Characterization of the Warpage Phenomenon .................. 37
3.1 Preliminary Remarks on Warpage Experiments ............. 37
3.2 Effect of Tool Surface Coarseness on Warpage
Deflections ............................................ 40
3.3 Warpage Deflections of Flat Unidirectional Specimens ... 41
3.4 Inspection of Laminate's Architecture by Means of
Microsection Analysis .................................. 45
3.5 Warpage Deflections of Flat MuJtiangle Specimens ....... 50
3.6 Warpage of Curved Thin Specimens ....................... 51
3.7 Cognitions from the Experimental Warpage
Investigations ......................................... 52
4 Investigation of the Spring-In Phenomenon ................... 55
4.1 Analytical Pre-examination of the Spring-in Effect ..... 55
4.2 Preliminary Remarks on Experimental Investigations ..... 55
4.3 Experimental Investigation on Spring-in Affecting
Parameters ............................................. 68
4.4 Statistical Analysis on obtained Spring-in Angles ...... 71
4.5 Extended Radford Approach .............................. 80
4.6 Experimental Quantification of Contributing Spring-In
Fractions .............................................. 90
4.7 Spring-in of Doubly Curved Areas and Nonlinear-Swept
Profiles ............................................... 93
4.8 Cognitions of the Spring-In Investigations ............. 97
5 Superposition of Distortion Mechanisms ...................... 99
5.1 Process Distortions of an Integral Composite Box
Structure ............................................. 102
5.2 Evaluation of the Forced-interaction Effect ........... 106
5.3 Cognitions from the investigation of the forced-
interaction effect .................................... 114
5.4 Numerical Analysis of T-Stiffener to Skin
Connection ............................................ 114
6 A Semi-Numerical Prediction Approach ....................... 123
6.1 Intention of the Model and its Area of Application ... 123
6.2 Model Derivation for Warpage of Flat Laminates ........ 123
6.3 Model Derivation for Spring-In of Single- and
Double-Curved Sections ................................ 127
6.4 Advanced Model Formulation ............................ 130
6.5 Limitation and Transferability ........................ 131
7 Verification by Means of Numerical and Experimental
Studies .................................................... 133
7.1 Application and Extension of the Warpage Prediction
Approach .............................................. 133
7.2 Numerical Verification for Warpage of Curved
Specimens ............................................. 135
7.3 Compensation of C-profile Process Distortions ......... 137
7.4 Spring-in Simulation for a Curved L-profile ........... 141
7.5 Spring-in of Curvature-Changing Structures ............ 144
7.6 Verification of the T-joint Tool by Experimental
Means ................................................. 149
7.7 Prediction of Process Distortions for the Integral
CFRP Box Structure .................................... 150
7.8 Consequences of Process Scattering on Box
Distortions ........................................... 157
7.9 Process Distortions of a Highly Integrated CFRP
Upper-Wing Cover ...................................... 159
7.10 Feasibility of the Tool-Compensation Approach ......... 165
8 Conclusions and Outlook .................................... 169
Appendix ...................................................... 173
A Verification of the Advanced Model Formulation .......... 173
В Experimental Study on Interply Slippage ................. 175
С Spring-in Prediction Tool in MATLAB ..................... 176
D Shrinkage - isotropic, anisotropic ...................... 178
Bibliography .................................................. 181
Own Publications .............................................. 187
Curriculum Vitae .............................................. 190
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