 | Gilliot A. Matrix influence on the impact tolerance of carbon composites made of non crimp fabric / Deutsches Zentrum für Luft- und Raumfahrt, Institut für Faserverbundleichtbau und Adaptronik, Braunschweig. - Köln: DLR, Bibliotheks- und Informationswesen, 2010. - xvii, 141 S.: Ill., graph. Darst. - (Forschungsbericht; 10-03). - Bibliogr.: p.132-141. - ISSN 1434-8454
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1 Introduction ................................................. 1
1.1 Non-crimp fabric composite in the aeronautics ........... 1
1.2 Impact hazards .......................................... 2
1.3 Objectives .............................................. 4
2 Literature Review ............................................ 5
2.1 Basics in carbon fibre reinforced composite ............. 5
2.1.1 Epoxy resin system ............................... 6
2.1.2 Benzoxazine resin system ........................ 14
2.2 Low velocity impact .................................... 16
2.3 Influence of non-matrix related properties ............. 17
2.3.1 Specimen geometry ............................... 17
2.3.2 Stacking sequence ............................... 18
2.3.3 Reinforcement ................................... 18
2.3.4 Fibre ........................................... 20
2.4 Influence of matrix related properties ................. 22
2.4.1 Fibre matrix adhesion ........................... 23
2.4.2 Neat resin system ............................... 27
2.4.3 Impact load behaviour ........................... 39
2.4.4 Interlaminar toughening ......................... 42
2.5 Compression strength after impact ...................... 50
2.5.1 Plain compression strength ...................... 50
2.5.2 Residual compression strength after impact ...... 50
2.6 Analysis of impact properties .......................... 53
2.6.1 Indentation ..................................... 53
2.6.2 Damage resistance ............................... 55
2.6.3 Residual Compression Strength ................... 60
2.7 Literature review summary .............................. 61
3 Experimental procedure ...................................... 63
3.1 Materials .............................................. 63
3.1.1 Reinforcement ................................... 63
3.1.2 Matrix .......................................... 63
3.2 Neat resin system sample ............................... 66
3.2.1 Neat resin system plate manufacturing ........... 67
3.2.2 Neat resin system test methods .................. 67
3.3 Composite sample ....................................... 68
3.3.1 Laminate manufacturing .......................... 68
3.3.2 Impact properties tests ......................... 70
3.3.3 Interlaminar fracture toughness ................. 74
4 Results and Discussion ...................................... 76
4.1 Neat resin system properties ........................... 76
4.1.1 Category I ...................................... 76
4.1.2 Category II ..................................... 78
4.1.3 Category III .................................... 79
4.1.4 Category IV ..................................... 79
4.1.5 Summary of neat resin system mechanical
results ......................................... 79
4.2 Composite impact tolerance ............................. 82
4.2.1 Unidirectional prepreg tape versus non-crimp
fabric .......................................... 82
4.2.2 Non-crimp fabric: Influence of the matrix ....... 85
4.2.3 Influence of the improvement of neat resin
system properties on the impact tolerance ....... 90
4.2.4 Interlaminar toughening of non-crimp fabric .... 104
4.2.5 Relationship between damage resistance and
damage tolerance ............................... 107
4.2.6 Impact load-time behaviour ..................... 112
4.2.7 Analytical analysis ............................ 122
5 Conclusion and Outlook ..................................... 127
5.1 Conclusion ............................................ 127
5.2 Outlook ............................................... 129
6 Appendix ................................................... 130
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