http://hdl.handle.net/10256/7143 2025-08-09T13:58:55Z http://hdl.handle.net/10256/26703 Characterization of the mixed-mode interlaminar fracture toughness of an additive manufacturing continuous carbon fiber reinforced-thermoplastic composite Santos, Jonnathan D.; Fotouhi, Sakineh; Guerrero Garcia, José Manuel; Blanco Villaverde, Norbert There is a lack of knowledge concerning the interlaminar fracture toughness under mixed-mode ratios of 3D-printed composites. In this work, several additive manufacturing (AM) continuous Fiber Reinforced Thermoplastic (cFRT) specimens have been tested to characterize the initiation and propagation of interlaminar fracture toughness under three different mixed-mode GII/(GI + GII) ratios: 25, 50, and 75%. The results obtained do not exhibit the common tendency seen in traditional laminated composite materials, in which the fracture toughness increases with the mixed-mode ratio. While the fracture toughness for the 50% mixed-mode ratio falls between the corresponding mode I and mode II values, the fracture toughness for the 25% and 75% ratios falls outside this range. To provide a reasonable explanation, fractography and microstructure analyses were conducted to quantify fiber, matrix, and void contents. It was concluded that this uncommon behavior is probably related to the intrinsic variability of the material and manufacturing process 2025-04-17T00:00:00Z http://hdl.handle.net/10256/26596 Discrete ply modelling of aeronautical intermediate-scale notched carbon fibre reinforced thermoplastic specimens subjected to multiaxial loading Guerrero Garcia, José Manuel; Bouvet, Christophe; Dufour, John-Eric; Serra, Joël Several finite element models developed at the mesoscale level are available for predicting the strength and failure progression of composite materials. However, this kind of damage models are commonly validated by comparing with typical coupon-scale testing specimens under uniaxial loading, which are not fully representative of aeronautical structures subjected to complex multiaxial loads. In this work, the Discrete Ply Model (DPM) is employed to reproduce intermediate-scale experimental tests carried out on carbon fibre reinforced thermoplastic samples, with a sharp central notch of 100 mm, tested in the VERTEX rig under tension, shear, and combined tension and shear loading. The tests show early buckling (particularly for the shear and combined cases) and development of post-buckling for almost the entire loading. The numerical results obtained demonstrate that the strengths, the fluxes as a function of the applied strains, deformed shapes, buckling modes, crack propagations and failure patterns are predicted with reasonable accuracy 2025-06-01T00:00:00Z http://hdl.handle.net/10256/26595 Micro-scale fiber/matrix stress concentrations in unidirectional glass/carbon hybrid composites under transverse loading Turan, Ecem; Guerrero Garcia, José Manuel; Lomov, Stepan V.; Sabuncuoglu, Baris Fiber/matrix interface stresses and micro-scale stress concentrations (SCs) under transverse loading were analyzed for hybrid composites, reinforced with glass and carbon fibers. A finite element model was implemented using parametric modeling technique to determine the stresses in the matrix and fiber/ matrix interface. Several micro-scale finite element models were generated for the analyses with various combinations of fiber material, fiber size, volume ratio and fiber spatial distribution models. Models with single fiber type (non-hybrid composites) were also analyzed to understand the hybridization effect on the stresses. The results reveal the effect of the presence of different fiber types and their arrangement on the micro-scale stress distributions and fiber/ matrix interface behavior. Under transverse loading, when the same type of fibers are aligned with the loading direction, the SCs on the stiffer fibers are larger than the case in the composite with the single stiffer fiber type. When these fibers are aligned with the direction perpendicular to the loading, the SCs on the stiffer fibers are lower. Fiber material type was more effective than the fiber size and fiber volume ratio enhances the effect of hybridization on the stress distributions. According to the authors' knowledge this is the first study investigating the transverse SCs in hybrid composites at the micro-scale level 2025-02-06T00:00:00Z http://hdl.handle.net/10256/26575 Real-Time Stringing Detection for Additive Manufacturing Charia, Oumaima; Rajani, Hayat; Ferrer Real, Inés; Domingo-Espin, Miquel; Grácias, Nuno Ricardo Estrela Additive Manufacturing (AM), commonly known as 3D printing, has gained significant traction across various industries due to its versatility and customization potential. However, the process remains time-consuming, with print durations ranging from hours to days depending on the complexity and size of the object. In many cases, errors occur due to object misalignment, material stringing due to nozzle overflow, and filament blockages, which can lead to complete print failures. Such errors often go undetected for extended periods, resulting in substantial losses of time and material. This study explores the implementation of traditional computer vision, image processing, and machine learning techniques to enable real-time error detection, specifically focusing on stringing-related anomalies. To address data scarcity in training machine learning models, we also release a new dataset and improve upon the results achieved by the Obico server model, one of the most prominent tools for stringing detection. Our contributions aim to enhance process reliability, reduce material wastage, and optimize time efficiency in AM workflows 2025-02-25T00:00:00Z