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The cellulose fibers that form washi are longer than those of regular paper made from wood pulp. Hence, the mechanical properties of washi can be higher than those of conventional paper. This study evaluated the magnetic, magnetostrictive, and tensile properties of negative magnetostrictive cobalt ferrite (CoFe2O4) particle dispersed handmade washi (washi−CoFe2O4). The CoFe2O4 additives magnetized the washi, which displayed negative magnetostriction with the fiber direction perpendicular to the magnetic field and in the parallel fiber direction. Concerning the mechanical properties, the washi−CoFe2O4 displayed an elongation of up to 77% after yielding. [ABSTRACT FROM AUTHOR]

Cracks induced by internal stresses compromise the structural integrity of ceramic laminates. Such stresses can be classified into thermal stress derived from thermal expansion mismatch and shrinkage stress derived from shrinkage mismatch. Analytical models have been proposed for the former, whereas only numerical predictions have been explored for the latter. In this study, an equation is constructed to predict the shrinkage stress by modifying an elastic solution proposed in previous studies. We fabricated laminates with three‐layer sandwiched structures using only alumina specimens with high and low densities to control the shrinkage and avoid thermal mismatch. Surface cracks were initiated when the shrinkage stress exceeded the flexural strength of the surface layer. Although the original strength of the surface layer was 308.8 MPa, the laminates' flexural strength was lower than that because of shrinkage constraint. Our results demonstrate that the shrinkage stress was successfully estimated analytically using a few material properties measured in an ordinary environment. This study will ensure the structural integrity of ceramic laminates in laminate designs. [ABSTRACT FROM AUTHOR]

Carbon-fiber-reinforced polymer (CFRP) is widely used in aerospace owing to its high strength, high elasticity, and low density. Recently, CFRP has been used at different temperatures, such as severe temperature environments near aircraft engines and cryogenic fuel tanks. Structural health monitoring (SHM) is needed to ensure the safe use of such structural components. Magnetostrictive materials are desirable candidates for SHM sensors owing to their ability to interconvert mechanical and magnetic energies and their excellent features, such as wide operating temperature range, long life, and low cost. In this study, iron–cobalt (Fe–Co) wires were embedded in CFRP composites (Fe-Co wire/CFRP composites), and their magnetic and magnetostrictive properties were evaluated. The magnetostriction was also analyzed using the nonlinear constitutive equation for magnetostrictive materials. Further, microstructural analysis was conducted, and the effect of microstructure on the magnetostriction of the specimens was analyzed. Finally, a four-point bending test was performed on the Fe–Co wire/CFRP composites at different temperatures, and the change in magnetic flux density with stress was measured. The obtained results serve as a reference for developing high-performance Fe–Co wire/CFRP composites for SHM sensors operating at high and cryogenic temperatures. [ABSTRACT FROM AUTHOR]

As sensor materials for structural health monitoring (SHM, a nondestructive test for the continuous evaluation of the conditions of individual structural components and entire assemblies), magnetostrictive materials, piezoelectric materials, and optical fibers have attracted significant interest. In this study, the mode I interlaminar fracture load and crack self-detection potential of glass fiber-reinforced polymer (GFRP)–embedded magnetostrictive Fe–Co fibers were investigated via double cantilever beam testing. The results indicated that by controlling the amount of Fe–Co fibers introduced into GFRP, the number of Fe–Co fibers could be reduced without compromising the performance of GFRP. Furthermore, the magnetic flux density increased significantly with crack propagation, indicating that the magnetic flux density change could determine crack propagation. [ABSTRACT FROM AUTHOR]