The purpose of the present survey is to review the analysis of composite materials from the applied mechanics and engineering science point of view. The subjects under consideration will be analysis of the following properties of various kinds of composite materials: elasticity, thermal expansion, moisture swelling, viscoelasticity, conductivity (which includes, by mathematical analogy, dielectrics, magnetics, and diffusion) static strength, and fatigue failure.

Analysis of Composite Materials—A Survey

A simple fatigue failure criterion for unidirectionally fiber reinforced laminae under oscillatory states of combined plane stress has been es tablished The criterion is expressed in terms of thre

https://apps.dtic.mil/sti/pdfs/ADA306222.pdf

A Fatigue Failure Criterion for Fiber Reinforced Materials.

Trabecular bone is a complex material with substantial heterogeneity Its elastic and strength properties vary widely across anatomic sites, and with aging and disease Although these properties depend very much on density, the role of architecture and tissue material properties remain uncertain It is interesting that the strains at which the bone fails are almost independent of density Current work addresses the underlying structure-function relations for such behavior, as well as more complex mechanical behavior, such as multiaxial loading, time-dependent failure, and damage accumulation A unique tool for studying such behavior is the microstructural class of finite element models, particularly the "high-resolution" models It is expected that with continued progress in this field, substantial insight will be gained into such important problems as osteoporosis, bone fracture, bone remodeling, and design/analysis of bone-implant systems This article reviews the state of the art in trabecular bone biomechanics, focusing on the mechanical aspects, and attempts to identify important areas of current and future research

Biomechanics of trabecular bone.

3D failure criteria for laminated fibre-reinforced composites, based on a physical model for each failure mode and considering non-linear matrix shear behaviour, are developed. Special emphasis is given to compression failure. The physical model for matrix compression failure is based on the Mohr–Coulomb criterion and also predicts the fracture angle. For fibre kinking, an initial fibre-misalignment angle is considered to trigger failure, due to further rotation during the compressive loading. The plane where the kinking takes place is predicted by the model, as well as the kink-band angle. Applications are presented that validate the model against experimental data.

Physically based failure models and criteria for laminated fibre-reinforced composites with emphasis on fibre kinking. Part II: FE implementation

Modelling bone tissue fracture and healing: a review ☆

An operationally simple strength criterion for anisotropic materials is developed from a scalar function of two strength tensors. Differing from existing quadratic approximations of failure surfaces, the present theory satisfies the invariant requirements of coordinate transforma tion, treats interaction terms as independent components, takes into account the difference in strengths due to positive and negative stresses, and can be specialized to account for different material symmetries, multi-dimensional space, and multi-axial stresses. The measured off-axis uniaxial and pure shear data are shown to be in good agreement with the predicted values based on the present theory.

/pdf/a-general-theory-of-strength-for-anisotropic-materials-1yq87ay1gm.pdf

A General Theory of Strength for Anisotropic Materials

The resolution of the components of strength tensors derived from experimental data is discussed. It is shown that the variations in the non- interaction components are independent of the tension-c...

Optimal Experimental Measurements of Anisotropic Failure Tensors

This note concerns the off-axis test of a hard orthotropic composite (graphite-epoxy) and the development of a fixture to reduce the shear coupling effect. In off-axis tests of orthotropic materials where the direction of applied traction is not co-incident with the principal elastic axis of the material, a rotation is induced. Pagano and Halpin [1] noted that in typical experimental tests where the specimen was rigidly clamped to the machine, the natural rotation of the ends was constrained and a non-homogeneous state of stress and strain is induced in the specimen. This effect was estimated analytically and demonstrated experimentally on a soft orthotropic composite (unidirectionally reinforced-rubber). In view of the wide use of off-axis tests in composite testing, it is timely to examine this shear-coupling effect in hard composites. In our investigation, a graphite-epoxy with elastic stiffness, Eii = 20 X 106 psi, E22 = 1 X 106 psi, V12 = .25, G = .6 X 106 psi, were used.

Edward M. Wu

Papers

A General Theory of Strength for Anisotropic Materials

Optimal Experimental Measurements of Anisotropic Failure Tensors

Off-Axis Test of a Composite