01 Dic Doctoral Thesis in Composite Materials
On November 28, Alex Fernández successfully defended his PhD thesis titled “Assessment of the out-of-plane behaviour of a 3D-printed carbon fibre reinforced composite material”at the University of Girona. His research was co-supervised by Dr. Norbert Blanco (Universitat de Girona) and Dr. Daniel Trias (Universitat de Girona).
About the research:
The main objective of the thesis is the experimental assessment of the out-of-plane response of an additively manufactured continuous carbon fibre reinforced polymer (c-CFRP) composite and the validation of numerical predictions with available damage models.
Key contribution:
•2TCT geometry was identified and validated as optimal for translaminar fracture toughness characterisation, minimising undesired failure modes.
•The fibre tensile translaminar fracture toughness (33.1 N/mm) and the associated cohesive law were obtained from the laminate results using a Rule of Mixtures approach.
•Quasi-static indentations and μCT revealed a damage sequence starting from micro-delaminations generated by voids, their progressive growth until the apparition of extensive ply damage and perforation.
•Conventional laminates present more distributed delaminations and intralaminar damage, while dispersed laminates have an earlier delamination onset with more localised delaminations at interfaces with larger mismatch angle. Similar observations for QSI and LVI tests.
•The out-of-plane performance is strongly influenced by the manufacturing variability produced by the presence of voids.
•Numerical models were developed and validated for LVI prediction in additive manufacturing c-CFRP. Shell elements and zero-thickness cohesive elements, combining CDM and CZM for intralaminar and interlaminar damage, respectively.
•Extensive intralaminar damage was predicted before delaminations, contrasting with the usual trend for traditional carbon/epoxy composites and the QSI observations.
•Numerical predictions of delaminations shape and location were aligned with IRT and μCT inspections. General underprediction of the projected delaminated area, especially in dispersed laminates.
•Dynamic loads in LVI affects the impact response compared to the QSI test results, evidencing strain-rate effects.
Explore some of his publications:
A. Fernández; N. Blanco; D. Trias; N. Gascons. Assessment of damage sequence in additive manufactured composite laminates under quasi-static out-of-plane loading. Composites Part A: Applied Science and Manufacturing 2024-09. DOI: 10.1016/j.compositesa.2024.108263
