Thermo-electro-mechanical microstructural interdependences in conductive thermoplastics

Additive manufacturing has enabled the design of thermoplastic components that provide structural support,electrical conductivity and heat generation modulated by mechanical deformation.The mechanisms and interplays that govern the material response at the microstructural level remain,however,elusive.Here,we develop an experimental method to characterise conductive filaments from a combined mechanical,electrical and thermal perspective.This approach is used to unravel exciting material interplays of conductive polylactic acid.To overcome experimental limitations that prevent a complete microstructural analysis of the problem,we develop a full-field homogenisation framework and implement it for finite elements.The framework accounts for viscoplasticity,electrical and thermal conduction,convection and heat generation via Joule effect,as well as for the interdependences between them.After experimental validation,the framework is applied to virtually optimise fabrication requirements to obtain desired properties in final products,i.e.,stiffer products,filaments with higher conductivities or with better sensing capabilities.

Hybrid magnetorheological elastomers enable versatile soft actuators

Recent advances in magnetorheological elastomers(MREs)have posed the question on whether the combination of both soft-and hard-magnetic particles may open new routes to design versatile multifunctional actuators.Here,we conceptualise ultra-soft hybrid MREs(≈1–10 kPa stiffness)combining experimental and computational approaches.First,a comprehensive experimental characterisation is performed.The results unravel that the magneto-mechanical performance of hybrid MREs can be optimised by selecting an adequate mixing ratio between particles.Then,a multi-physics computational framework provides insights into the synergistic magneto-mechanical interactions at the microscale.Soft particles amplify the magnetisation and hard particles contribute to torsional actuation.Our numerical results suggest that the effective response of hybrid MREs emerges from these intricate interactions.Overall,we uncover exciting possibilities to push the frontiers of MRE solutions.These are demonstrated by simulating a bimorph beam that provides actuation flexibility either enhancing mechanical bending or material stiffening,depending on the magnetic stimulation.