The mechanical properties of platelet reinforced composites

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Abstract

The effective moduli of platelet reinforced media are derived for aligned and randomly oriented circular platelets at both dilute and finite concentrations. The platelets are modeled as very thin oblate spheroids in which edge effects caused by the presence of the sharp corners can be significant, depending upon the relative magnitudes of the thickness-to-diameter ratio and the ratio of the matrix stiffness to that of the reinforcer. The edge effects become negligible when the latter ratio greatly exceeds the former, in which case the platelets act effectively as infinite layers. In general, the non-uniform stress fields in the vicinity of the sharp corners or edges cause a reduction in the effective moduli. When the aspect ratio greatly exceeds the stiffness ratio, the inclusions become equivalent to rigid disks, and the pertinent concentration parameter is not the volume fraction, which is zero, but a number analogous to the crack density parameter for solids containing cracks. Effective medium theories for finite concentrations of rigid disks predict that the effective Poisson's ratio tends to the value 0.1557… as the concentration increases, and the self-consistent theory displays a critical disk density at which the composite becomes rigid.

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  • Strength analysis of bio-inspired composites reinforced by regularly and randomly staggered platelets

    2019, Composite Structures
    Citation Excerpt :

    When subjected to loads, the mineral platelet and the protein matrix provide stiffness and toughness to the composite, respectively, which conduces to their remarkable mechanical properties. Also, composite materials like nacre have similar mechanical properties in both directions [3] as platelets can reinforce the matrix in the whole plane parallel to the platelet, while the fiber reinforced composite obtains the comparable characteristic only by complex process such as laying and weaving. By mimicking the microstructure of nacre, many different kinds of materials were used as reinforcing platelets, including graphite [4–7], SiC [8,9], clays [10–12] and grapheme [13–16], to fabricate platelet reinforced composites.

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