Influence of pre-cure stage upon exothermic overshoot and defects from deposition of continuous CFRP tow in AM

Taddei, Francesco (2021) Influence of pre-cure stage upon exothermic overshoot and defects from deposition of continuous CFRP tow in AM. [Laurea magistrale], Università di Bologna, Corso di Studio in Aerospace engineering / ingegneria aerospaziale [LM-DM270] - Forli', Documento ad accesso riservato.
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Abstract

This study investigates the influence of the introduction of a pre-curing stage in Additive Manufacturing of continuous CFRP tows upon the exothermic overshoot and the defects generated during the deposition of the pre-cured material. This additive process aims at combining benefits from AM of CFRP laminates with the necessity of reducing the temperature overshoot during the cure of thermosetting polymers. Thermo-chemical properties of the epoxy resin XB3515 have been characterized. An FE model addressing the cure simulation has been also developed using the FE solver Abaqus, and validated. Pre-cured laminates have been manufactured to investigate the effect of the pre-cure level upon temperature overshoot and deposition-induced defects. The findings point out that the introduction of a pre-curing unit can reduce the temperature overshoot within the Carbon/Epoxy laminate and, therefore, cure-induced residual stresses. However, the following deposition phase limits the choice of the pre-cure level. A value between 20% and 30% reduces the thermal gradient by more than 90% generating in-plane waves with a severity that should not compromise the mechanical performances of the component; in particular, the compressive strength should be reduced by 2%-10%.

Abstract
Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Taddei, Francesco
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Ordinamento Cds
DM270
Parole chiave
Additive Manufacturing, CFRP, epoxy resin, residual stresses, exothermic overshoot, pre-curing, cure FE model, in-plane waviness, tow deposition
Data di discussione della Tesi
16 Dicembre 2021
URI

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