Search

The paper deals with analysis of relationships between the microgeometry and mechanical properties of fiberglass i.e. epoxy resin composites with random fibers distribution. The mechanical properties (e.g. a flexural modulus E f , taking into account shear effects) of the material were determined in bending by Short Beam Shear Tests (SBST). Microgeometry of the structure was characterized on the basis of microscopic images of test specimens. The paper proposes a new measure of irregular reinforcement distribution expressed as an area ratio of the matrix surrounding the single fiber to the circuit of the fiber. The measure, denoted by G AB , is expressed in microns. In particular the relationship between the results obtained in the test samples with random distribution of fibers and theoretical regular structures of square (K) and hexagonal (H) type is presented. Specimens of the investigated composite (E-glass fibers and Epidian 5 epoxy resin), supplied by industrial partner, were cut out from raw material of helicopter blades girders. The obtained experimental results for the analyzed composite corresponded to approximation by the theoretical model of the square (K) type. The results can be used to estimate the flexural elastic modulus E f of the unidirectional composites with irregular arrangement of fibers, made manually or using the molding apparatus. Based on those results, it can be concluded that the square distribution model (K) is appropriate for numerical estimation of the strength composites properties reinforced with glass fibers of circular cross-section, having the diameter in the range of 10–16 μm. [ABSTRACT FROM AUTHOR]

Highlights: [•] The XFEM and the R&T techniques were exploited in damage analysis of the WC/Co microstructure. [•] Damage propagation analysis was performed with 2-D numerical models. [•] The Gurson–Tvergaard material porosity was used for the description of the Co interface. [•] Traction–Separation and Ductile Damage Criterions were used to model the WC/Co composite damage process. [Copyright &y& Elsevier]

Stress intensity factors for a kinked crack originating at interface of two bonded dissimilar materials subjected to normal tension are found by the finite element method. [ABSTRACT FROM AUTHOR]

The effect of molybdenum additions on the phases, microstructures, and mechanical properties of pre-alloyed Ti6Al4V was studied through the spark plasma sintering technique. Ti6Al4V-xMo (where x = 0, 2, 4, 6 wt.% of Mo) alloys were developed, and the sintered compacts were characterized in terms of their phase composition, microstructure, and mechanical properties. The results show that the equiaxed primary alpha and Widmänstatten (alpha + beta) microstructure in pre-alloyed Ti6Al4V is transformed into a duplex and globular model with the increasing content of Mo from 0 to 6%. The changing pattern of the microstructure of the sample strongly influences the properties of the material. The solid solution hardening element such as Mo enhances mechanical properties such as yield strength, ultimate tensile strength, ductility, and hardness compared with the pre-alloyed Ti6Al4V alloy. [ABSTRACT FROM AUTHOR]

Metal-ceramic composite (MCC) materials can be used for manufacturing high-responsibility structures such as jet engines or cutting tools. One example of these materials is a two-phase wolfram carbide (WC) and cobalt (Co) composite. This MCC is a combination of hard WC grains with a Co metallic ductile binder. The resulting microstructure is a combination of two phases with significantly different mechanical behaviors. In this study, we investigate impact conditions, starting with an illustrative example of the Taylor impact bar where—although the process is very rapid—the equivalent plastic strain and temperature are higher in the adiabatic solution than those in the coupled solution. On exposing the WC/Co composite with a metallic binder to impact loading, heat is generated by plastic deformation. If the process is fast enough, the problem can be treated as adiabatic. However, a more common situation is that the process is slower, and the heat is generated in the ductile metallic binders. As a result, the associated grains are heated due to the conduction effect. Consequently, the process should be treated as coupled. When the impact is applied over a short time period, maximum temperatures are significantly lower if the process is analyzed as coupled rather than as adiabatic. The grains are immediately affected by temperature increase in the binders. Therefore, the heat conduction effect should not be omitted. [ABSTRACT FROM AUTHOR]

The modern polycrystalline composite materials have a complex internal structure consisting of different phases and interfaces with random distribution. Relevant examples are Al 2 O 3 /ZrO 2 , i.e. alumina/zirconia composites, widely used as structural materials with applications ranging from aerospace to bio-engineering. Depending on the phases content and on the grain size a broad range of material characteristics, among which elastic constants, can be obtained. With the aim of characterizing this class of materials, we exploit a numerical Fast Statistical Homogenization Procedure (FSHP) in order to both estimate the size of the Representative Volume Elements (RVE) and the effective elastic properties, assuming a linear elastic material behaviour. The 2-D analyses are performed considering a microstructure inspired by images of real portions of the Al 2 O 3 /ZrO 2 composite obtained from a scanning electron microscope. The recent Virtual Element Method is used in combination with the FSHP approach to numerically solve boundary value problems. Different volume contents of phases are considered ranging from pure Alumina to pure zirconia. The results are useful to reliably characterize such materials in the elastic range taking into account the role played by random distribution of grains. [Display omitted] • Homogenization of random Ceramic Matrix Composites (CMC). • Fast identification of the homogenized moduli with the Virtual Element Method. • Parametric analysis. [ABSTRACT FROM AUTHOR]