Theory of elastic-plastic deformation of randomly reinforced composite materials

In this study the double-inclusion model, originally developed to determine the effective linear elastic properties of composite materials, is reformulated in incremental form and extended to predict the effective nonlinear elastic–plastic response of two-phase particulate composites reinforced with spherical particles. The study is limited to composites consisting of purely elastic particles and elastic–plastic matrix of von Mises yield criterion with isotropic strain hardening. The resulting nonlinear problem of elastic–plastic deformation of a double inclusion embedded in an infinite reference medium (that has the elastic–plastic properties of the matrix) subjected to an incrementally applied far-field strain is linearized at each load increment through the use of the matrix tangent moduli. The proposed incremental double-inclusion model is evaluated by comparison of the model predictions to the exact results of the direct approach using representative volume elements containing many particles, and to the available experimental results. It is shown that the incremental double-inclusion formulation gives accurate prediction of the effective elastic–plastic response of two-phase particulate composites at moderate particle volume fractions. In particular, the incremental double-inclusion model is capable of capturing the Bauschinger effect often exhibited by heterogeneous materials. A unique feature of the proposed incremental formulation is that the composite matrix is treated as a two-phase material consisting of both an elastic and a plastic region.

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MODELLING OF ELASTIC-PLASTIC DEFORMATION OF POLYCRYSTALLINE AND COMPOSITE MATERIALS UNDER LOADING

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:19913134 ◽

1991 ◽

Vol 01 (C3) ◽

pp. C3-949-C3-954

Author(s):

V. N. LEYCIN ◽

P. V. MAKAROV ◽

A. P. NIKOLAEV ◽

I. Y. SMOLIN

Keyword(s):

Plastic Deformation ◽

Composite Materials ◽

Elastic Plastic

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In-Situ Observations of Microscale Ductility in a Quasi-Brittle Bulk Scale Epoxy

Polymers ◽

10.3390/polym12112581 ◽

2020 ◽

Vol 12 (11) ◽

pp. 2581 ◽

Cited By ~ 1

Author(s):

Olivier Verschatse ◽

Lode Daelemans ◽

Wim Van Paepegem ◽

Karen De Clerck

Keyword(s):

Plastic Deformation ◽

Composite Materials ◽

Epoxy Resin ◽

Deformation Behavior ◽

Fiber Reinforced Composite ◽

Reinforced Composite ◽

Reinforcing Fibers ◽

The Matrix ◽

Bulk Scale

Fiber reinforced composite materials are typically comprised of two phases, i.e., the reinforcing fibers and a surrounding matrix. At a high volume fraction of reinforcing fibers, the matrix is confined to a microscale region in between the fibers (1–200 µm). Although these regions are interconnected, their behavior is likely dominated by their micro-scale. Nevertheless, the characterization of the matrix material (without reinforcing fibers) is usually performed on macroscopic bulk specimens and little is known about the micro-mechanical behavior of polymer matrix materials. Here, we show that the microscale behavior of an epoxy resin typically used in composite production is clearly different from its macroscale behavior. Microscale polymer specimens were produced by drawing microfibers from vitrifying epoxy resin. After curing, tensile tests were performed on a large set of pure epoxy microfiber specimens with diameters ranging from 30 to 400 µm. An extreme ductility was observed for microscale epoxy specimens, while bulk scale epoxy specimens showed brittle behavior. The microsized epoxy specimens had a plastic deformation behavior resulting in a substantially higher ultimate tensile strength (up to 380 MPa) and strain at break (up to 130 %) compared to their bulk counterpart (68 MPa and 8%). Polarized light microscopy confirmed a rearrangement of the internal epoxy network structure during loading, resulting in the plastic deformation of the microscale epoxy. This was further accompanied by in-situ electron microscopy to further determine the deformation behavior of the micro-specimens during tensile loading and make accurate strain measurements using video-extensometry. This work thus provides novel insights on the epoxy material behavior at the confined microscale as present in fiber reinforced composite materials.

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