Bioinspired Functionally Graded Nanocomposites Synthesized Through Magnetophoretic Processes for Tailored Stress Reducti
- PDF / 2,159,824 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 86 Downloads / 138 Views
Bioinspired Functionally Graded Nanocomposites Synthesized Through Magnetophoretic Processes for Tailored Stress Reduction Tommaso Nardi, Yves Leterrier * and Jan-Anders E. Månson Laboratoire de Technologie des Composites et Polymères (LTC) École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland ABSTRACT Through a unique combination of magnetophoretic and photopolymerization processes, approximately 150 µm thick functionally graded films based on a UV-curable matrix and containing Fe3O4@SiO2 core-shell nanoparticles are synthesized. Owing to their continuous composition gradients and to the considerable variations in elastic modulus (up to ≈70 %) when going from particle-depleted to particle-enriched regions, such materials are highly efficient in reducing the mechanical stress arising from thermal variations, therefore improving the material efficiency towards durability and delamination problems. INTRODUCTION It is well known how many bio-composites such as bamboo [1-3], tissue interfaces [4] and teeth [5] are able to increase their mechanical performances and minimize stresses arising from environmental loads through a hierarchical organization of their constitutive elements. Not only functionally graded materials (FGM) can efficiently reduce the detrimental effects associated to external mechanical loads, but they can also minimize stresses arising from thermal mismatches between the graded coating and the substrate when these are subjected to temperature ramps. [6,7] In this study, we first propose a synthetic strategy for functionally graded materials based on the application of a magnetic field gradient on polymeric composite coatings filled with surface functionalized Fe3O4@SiO2 nanoparticles. We show how starting from a homogeneous dispersion of nanoparticles in the uncured polymeric matrix, coatings exhibiting tailored gradients in particles concentration and corresponding gradients in elastic moduli can be synthesized. We then compute the thermal stresses within the coating and at the coating-substrate interface for various graded morphologies (Figure 1). We demonstrate how such graded structures improve thermal stress distribution compared to the homogeneous case, efficiently reducing the micromechanical stresses deriving by temperature treatments, both at the manufacturing stage and during lifetime.
ϕ(z)
ϕ(z)
ϕ(z)
homogeneous)) composite)coa/ng)
linear)gradient)) composite)coa/ng)
S5shape)gradient)) composite)coa/ng)
substrate)
substrate)
substrate)
Figure 1. Schematic illustration of the three analyzed structures, i.e. homogeneous (left), linear gradient (center) and S-shape gradient (right) composite coatings on a substrate. φ(z) stands for the thickness (z) dependence of the nanoparticle volume fraction φ.
Page 2 of 7
EXPERIMENTAL DETAILS DETAILS EXPERIMENTAL The synthetic synthetic procedures procedures for for Fe Fe33O O44 nanoparticles nanoparticles and and 3-methacryloyloxypropyl 3-methacryloyloxypropyl The trimethoxysilane (MPS) functionalized Fe O @SiO co
Data Loading...
