Notice bibliographique
Résumé
Structural configurations in helicopter rotor systems often contain plies of 0° and 45° to resist centrifugal and torsional loads. Delaminations in test specimens that are tested to failure often experience delaminations between a 0°/45° ply interface. However, the standard methods to characterize delamination utilize a unidirectional 0° specimen. The reasons for using a unidirectional layup are that multidirectional beams suffer from ply cracks in the nonzero plies, increased anticlastic bending and other effects. This work investigated the issues for testing a nonunidirectional double cantilever beam (DCB) specimen with a delamination in a 0°/45° interface. Several criteria were developed to minimizethe effects noted above. These included reduction of bend twist coupling and residual thermal stresses, prevention of nonzero ply breakage, and minimized anticlastic bending. The resulting layup consisted of a 64-ply laminate of 0°, 45°, and -45° plies. Quasi-static and fatigue tests were conducted on unidirectional layups and the new configuration fabricated from S2/E773 glass/epoxy. For both the static and fatigue tests the delamination grew and remained in the 0°/45° interface for a significant portion of delamination growth. Crack branching was noted in some specimens as the delamination length became longer. The interlaminar fracture toughness, GIc, of the 0°/45° DCBs had more scatter and a 10% lower mean than the 0° DCB specimens. Both specimens experienced fiber bridging shown by an increase in GIc with delamination growth and observation of the delaminated surfaces. The influence of the fiber bridging was similar in the two specimen configurations. The fatigue delamination onset curves of the two specimen configurations were coincidentally not showing the scatter or lower values seen in the static tests. The static and fatigue results indicate that the use of 0° specimens for characterizing delamination in a 0°/45° interface is satisfactory for the materials tested in this work. However, the presence of fiber bridging in the 0°/45° specimens indicates that using the initiation value for predicting delamination growth may be overly conservative when fiber bridging is present. The same fiber bridging has also been observed in failure surfaces on structural components tested to failure. While the inclusion of fiber bridging in delamination growth predictive models is possible, further work should be conducted on the parameters that affect fiber bridging, such as thickness, processing and crack opening, to ensure that the properties from a DCB specimen are representative of that in the structures. Work on other material systems, other delamination modes and fatigue crack growth is also recommended.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».