This study explores the shape-morphing behavior of 4D-printed structures made from Polylactic Acid (PLA), a prominent bio-sourced shape-memory polymer. Focusing on the response of these structures to thermal stimuli, this research investigates how various printing parameters influence their morphing capabilities. The experimental approach integrates design and slicing, printing using fused deposition modeling (FDM), and a post-printing activation phase in a controlled laboratory environment. This process aims to replicate the external stimuli that induce shape morphing, highlighting the dynamic potential of 4D printing. Utilizing Taguchi’s Design of Experiments (DoE), this study examines the effects of printing speed, layer height, layer width, nozzle temperature, bed temperature, and activation temperature on the morphing behavior. The analysis includes precise measurements of deformation parameters, providing a comprehensive understanding of the morphing process. Regression models demonstrate strong correlations with observed data, suggesting their effectiveness in predicting responses based on control parameters. Additionally, finite element analysis (FEA) modeling successfully predicts the performance of these structures, validating its application as a design tool in 4D printing. This research contributes to the understanding of 4D printing dynamics and offers insights for optimizing printing processes to harness the full potential of shape-morphing materials. It sets a foundation for future research, particularly in exploring the relationship between printing parameters and the functional capabilities of 4D-printed structures.
The present study deals with the numerical modelling of hybridlaminated composites, which can be proved especially useful in theengineering and maintenance of advanced aerospace primary structures. Thelamina is comprised of continuous carbon fibers, thermosetting epoxypolymer matrix, as well as carbon nanostructures, such as graphene orcarbon nanotubes, inclusions. Halpin-Tsai equations combined with resultsobtained from nanomechanical analysis are employed in order to evaluatethe elastic properties of the carbon nanostructure/polymer matrix. Then, theobtained elastic properties of the hybrid matrix are used to calculate theorthotropic macro-mechanical properties of the unidirectional compositelamina. A hybrid composite plate is modelled as a 2D structure via theutilization of 4-node, quadrilateral, stress/displacement shell finite elementswith reduced integration formulation. The convergence and analysisaccuracy are tested. The mechanical performance of the hybrid compositesis investigated by considering specific configurations and applyingappropriate loading and boundary conditions. The results are compared withthe corresponding ones found in the open literature, where it is possible.
Two large-scale diesel pool fire engulfment testswere carried out on LPG tanksprotected with intumescing materials to test the effectiveness of thermal coatings in the prevention of hot BLEVE accidental scenarios in the road and rail transport of LPG. A specific test protocol was defined to enhance reproducibility of experimental tests. The geometrical characteristics of the test tanks were selected in order to obtain shell stresses similar to those present in full-size road tankers complying to ADR standards. In order to better understand the stress distribution on the vessel and to identify underlying complicating phenomena, a finite element model was also developed to better analyze the experimental data. A non-homogeneous and time-dependent effectiveness of the fire protection given by the intumescing coating was evidenced both by finite element simulations and by the analysis of the coating after the tests. The results of the fire tests pointed out that the coating assured an effective protection of the tanks, consistently increasing the expected time to failure. The data obtained suggest that the introduction of fire protection coatings may be a viable route to improve the safety of the LPG distribution chain.
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