The effort on the development of aeronautical structures produced with thermoplastic composite materials has increased in the last years, however in literature there are few studies concerning the interlaminar properties of Carbon fibers (CF)/poly-ether-ketone-ketone (PEKK) laminates obtained with out-of-autoclave (OoA) consolidation processes. In this work the interlaminar properties of an unidirectional CF/PEKK thermoplastic prepreg system, known with the commercial name APC are studied. The material is consolidated through OoA techniques and the research is focused mainly on the mode I loading condition. The behavior is studied both experimentally and numerically, thanks to the development of a mesoscale FE model of the mode I delamination. The study shows how the fiber distribution plays a key role in the overall fracture resistance of the laminate and how the consolidation pressure has a great influence on it. Therefore, a microscale FE model is developed to further study the fracture behavior within the microstructure of the unidirectional laminates. The long term effects on the composite are studied through an experimental investigation on the interlaminar properties of unidirectional laminates subjected to moisture saturation, freeze-thaw cycling and fatigue loading. Finally, the mechanical behavior of a laminates obtained through automated manufacturing of the thermoplastic composite is investigated. A laminate was manufactured through AFP in-situ consolidation and its mechanical behavior is compared with laminates consolidated in autoclave and heated press.
Negli ultimi anni è cresciuto l'interesse per lo sviluppo di strutture aeronautiche realizzate con materiali compositi termoplastici. Tuttavia, insufficienti studi sulle proprietà interlaminari dei laminati CF/PEKK prodotti con processi di consolidamento fuori autoclave (OoA) sono presenti in letteratura. In questo studio sono state esaminate le proprietà interlaminari dei laminati APC (PEKK/CF AS4D 12K) consolidati OoA, concentrandosi principalmente sulle condizioni di carico in modo I. Il comportamento è stato analizzato sia sperimentalmente che numericamente, grazie allo sviluppo di un modello agli elementi finiti (FE) a mesoscala della delaminazione in modo I. La ricerca ha evidenziato come la distribuzione delle fibre sia fondamentale per la resistenza alla frattura del laminato e come la pressione di consolidamento influisca significativamente su di essa. Per approfondire lo studio del comportamento alla frattura all'interno della microstruttura dei laminati unidirezionali, è stato sviluppato un modello FE a microscala. Gli effetti a lungo termine sui compositi sono stati investigati sperimentalmente, esaminando le proprietà interlaminari dei laminati unidirezionali esposti a saturazione di umidità, cicli di gelo-disgelo e carichi di fatica. Infine, è stato esaminato il comportamento meccanico di un laminato realizzato mediante produzione automatizzata di compositi termoplastici. Un laminato è stato prodotto tramite consolidamento in situ AFP e il suo comportamento meccanico è stato confrontato con quello di laminati consolidati in autoclave e consolidati tramite pressa a piani caldi.
Interlaminar properties of out-of-autoclave consolidated thermoplastic composites
Chemello, Enrico
2023/2024
Abstract
The effort on the development of aeronautical structures produced with thermoplastic composite materials has increased in the last years, however in literature there are few studies concerning the interlaminar properties of Carbon fibers (CF)/poly-ether-ketone-ketone (PEKK) laminates obtained with out-of-autoclave (OoA) consolidation processes. In this work the interlaminar properties of an unidirectional CF/PEKK thermoplastic prepreg system, known with the commercial name APC are studied. The material is consolidated through OoA techniques and the research is focused mainly on the mode I loading condition. The behavior is studied both experimentally and numerically, thanks to the development of a mesoscale FE model of the mode I delamination. The study shows how the fiber distribution plays a key role in the overall fracture resistance of the laminate and how the consolidation pressure has a great influence on it. Therefore, a microscale FE model is developed to further study the fracture behavior within the microstructure of the unidirectional laminates. The long term effects on the composite are studied through an experimental investigation on the interlaminar properties of unidirectional laminates subjected to moisture saturation, freeze-thaw cycling and fatigue loading. Finally, the mechanical behavior of a laminates obtained through automated manufacturing of the thermoplastic composite is investigated. A laminate was manufactured through AFP in-situ consolidation and its mechanical behavior is compared with laminates consolidated in autoclave and heated press.File | Dimensione | Formato | |
---|---|---|---|
Phd_tesi_enrico_chemello.pdf
non accessibile
Dimensione
102.12 MB
Formato
Adobe PDF
|
102.12 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/222750