Mechanical Behavior Of Composites Research Articles

Cauchy singular integral equations with logarithmically singular integrands in solid mechanics

However, for some boundary value problems the weight function is logarithmically singular and is of the form w(t) = log{(l+t)/(l-t)}. (5) Examples of problems with such weight functions include the analytical simulations of fiber pull out or fracture of fiber-reinforced composites with imperfect fiber-matrix interfaces. Solution of such problems in composites, where imperfection in fiber-matrix interfaces is accounted for, are becoming important in the development of more physically realistic models for studying the mechanical behavior of composites.

Novel Composite Microstructure and Mechanical Behavior of Mollusk Shell

Preliminary investigations of the microstructure/mechanical properties relationship in a mollusk shell—the large conch, Strombus gigas—are reported. Strombus gigas has the well‐ordered “crossed lamellar” microstructure and, in four‐point bending, is remarkably tough in certain orientations, permitting noncatastrophic (“graceful”) failure. Fractography indicates that several toughening mechanisms are acting in concert, including crack bridging, microcracking, fiber pullout, and microstructurally induced crack arrest branching. Microindentation studies show that this material is very resistant to cracking; the damage zones around the indents strongly reflect the lamellar character of the microstructure.

Mechanical behavior of microstrip structures made from YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting ceramics

The thermal stress response of YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting microstrip lines on GaAs, Si, Al/sub 2/O/sub 3/ and MgO dielectric substrates was studied using the finite-element method. Detailed stress distributions near critical areas of the systems were calculated to understand the composite mechanical behavior. It is shown that the resulting stress fields are very high (large enough to cause cracking in the composite structure) for some of the dielectric materials due to the thermal expansion mismatch between the superconducting material and the dielectric substrate materials. YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting microstrip lines in MgO displayed the best thermal mechanical properties of the four dielectric materials.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Damage mechanics for 3-D composites

This paper deals with tridirectional composite material mechanical behaviour. The different constituents of the composite material are fibre-yarns, matrix and their respective interfaces. The mechanical behaviours of these constituents are built up for each of them. They are characterised by some parameters from the elastic domain, up to the rupture. These parameters are identified by using classical and original tests on a tridirectional carbon-carbon composite. Micro-macro mechanical relationships are then given. They derive from simple physical ideas and are founded on damage notion and homogenisation theory. This approach completes another mechanical model of the homogeneous behaviour for this material. Comparisons between the theoretical and experimental results are given.

Non-equilibrium phase distribution in an Al-SiC composite

The phase distribution in an Al-SiC composite has been investigated using high resolution analytical electron microscopy. Particular attention was focused on Al-SiC interfaces, matrix boundaries and impurity phases which would impede the easy glide of dislocations. Small crystallites of MgO were distributed singly and in clusters along Al-SiC interfaces in all specimens. Interfacial segregation and precipitation involving alloy species apparently affected precipitation in the matrix, where the distribution of phases was found to be very heterogeneous. Matrix phases also included unusually large constituent particles and dispersoids, a consequence of the composite processing methods. The relationship between the observed microstructure and the composite mechanical behavior reported by others is discussed. The heterogeneous distribution of matrix phases is expected to result in a wide variation in local yield stress and local work-hardening rate within the composite.

Mechanical behaviour of a short-fibre composite

A theoretical investigation of the stress-field in a short-fibre composite is performed. The concept of a typical region is introduced and the boundary conditions for such a region, when the composite is imposed to a simple macroscopic loading, are derived. Using these boundary conditions, the stresses are calculated by integrating Navier's equations over the same region. Knowing this stress-field, macroscopic properties are calculated and conclusions are drawn about the mechanical behaviour of the composite, like critical fibre length and fracture toughness, when the geometry and mechanical properties of the constituents are varied.

Deformation and fracture behavior of stator windings subjected to bending loads

This paper presents the deformation and fracture behavior of stator windings subjected to bending loads. A series of bending tests were carried out on four kinds of stator windings, which were composed of steel solid bar or copper strands and mica-splitting tapes, and were impregnated with epoxy and polyester resins. The strain produced on the insulation surface and the deflection of the stator windings were measured, applying uniform bending moment to the stator windings up to failure. The tan? characteristics were also measured in order to detect the occurrence of mechanical damage produced in the insulation system. A preliminary bending stress and deflection analysis was made and then compared with the experimental results. From these studies, the relationship between the component properties and the composite mechanical behavior of the stator windings is clarified. The failure mechanism of the stator windings is also revealed.

The effect of axial residual stress on the mechanical behaviour of composites : Weiss, H.J. Journal of Materials Science Vol 12 (April 1977) pp 797–809

The effect of axial residual stress on the mechanical behaviour of composites : Weiss, H.J. Journal of Materials Science Vol 12 (April 1977) pp 797–809

The effect of axial residual stress on the mechanical behaviour of composites

The effect of axial residual stress on the properties of continuous fibre composites is calculated. It is emphasized that composite strength should be considered as a more complex phenomenon than usually done so by merely considering ultimate strength. It is shown that the information contained in σ(e)-curves if plotted in a more suitable form as hysteresis and set versus total strain, taking into account residual stress, may be a useful means for characterizing the composite and for detecting deviations from perfect structure. Conclusions are derived as to how composite performance may be improved. The results are substantiated by metallic composite data.

The mechanical properties of oriented discontinuous fiber‐reinforced thermoplastics. I. Unidirectional fiber orientation

AbstractThe mechanical properties of a series of thermoplastics reinforced with unidirectionally oriented short fibers are reported. Both organic and inorganic fiber reinforcements were used in fiber volume fractions of 0.10 to 0.50. A number of these composites were found to have excellent strength and stiffness properties combined with good toughness and low density. The dependence of composite properties on the properties of the constituent materials is discussed. Fiber efficiency factors for strength and modulus are presented and models for predicting composite mechanical behavior are reviewed.

Basic Mechanics of Fiber Reinforced Composite Materials

This paper is an introduction to the basic mechanics of fiber reinforced composite materials. Emphasis is placed on describing the general approach to composite prob lems and how principles of mechanics can be utilized in predicting composite mechanical behavior. Some description of composite materials and their fabrication is also in cluded. Because of the anisotropic and non-homogeneous character of these materials, basic principles of anisotropic mechanics and application of these principles to composite materials are discussed.