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The reinforced efficiency of steel fibers in composites is closely related to their spatial orientation, which can be generally driven by the external magnetic force and restricted by the wall effect of rigid boundaries of the container. To clarify the spatial orientation of steel fibers in composites considering the effect of rigid boundaries under the electromagnetic field, a series of two-phase models consisting of fibrous particles and homogeneous matrix are generated, in which the fibers are separately simplified as spherocylindrical, cylindrical, and linear particles. Based on these models of the semi-periodic boundaries, the effect of fiber characteristics (e.g., the fiber content V f, fiber aspect ratio ε, fiber length l sf, and fiber style) on both the spatial distribution and orientation degree of fibrous particles is studied before and after the fibers are aligned by the magnetic force. The results revealed that (1) both the effective number N A and orientation degree ξ of fibrous particles at a cross-section of the container can be greatly increased when the electromagnetic field is applied and (2) the wall effect of rigid boundaries shows an adverse impact on the amelioration of N A and ξ, and the range size of the affected region is essentially equal to the effective length of fibrous particles of different shapes (e.g., l sf + D sf) for spherocylindrical particles and l sf for cylindrical and linear particles).

Surface modification of poly(benzoxazole-imide) (PI) film was carried out by means of oxygen plasma treatment. A flexible copper clad laminate (FCCL) was fabricated using Ni-Cr ion implantation and electro-Cu plating process. Controlling the constant pressure, the effects of such treatment conditions as power and time were systematically investigated on the surface roughness, chemical composition and interface adhesion with Cu. It is found that the optical parameters for production of FCCL with excellent adhesion and solder resistance are 50 W/5 min and 100 W/10 min, respectively. Suitable roughness, reactive radical with high content pendent oxygen group, and metal-oxazole complex help to endow exceptional adhesive property to the interface of PI/Cu. And the peel strength of FCCL prepared from PI film with such modified surface rises by 60%.

To effectively reduce vibration, a metamaterial beam with carbon fiber-reinforced polymer (CFRP) is proposed. The dispersion curves are calculated by the transfer matrix method (TM). The frequency response is investigated by the spectral element method (SEM). Displacement fields at different representative frequencies are displayed by the finite element method (FEM). The effects of the geometry, material parameters, and cross-ply angle of CFRP on the band gap are considered numerically, three types of beams are discussed and compared. From the results, it was found that the cross-ply angle and length of CFRP have significant influence on the band gaps. The frequency and width of the band gaps are different when the CFRP layers are imparity. Finally, a CFRP beam with ten periods was fabricated and the experiment was carried out to test transmission characteristics. Although the number of periods is only ten, it was found that the experimental results agree well with the numerical results in the low-frequency range. The results obtained in the paper can provide some useful reference for understanding and optimization of the design for metamaterial beam with wide band gaps, lightweight and high strength. [ABSTRACT FROM AUTHOR]