Material: anisotropic 29 brittle

Although much as been done, much work remains. Improved material models for anisotropic materials, brittle materials, and chemically reacting materials challenge the numerical methods to provide greater accuracy and challenge the computer manufacturers to provide more memory and speed. Phenomena with different time and length scales need to be coupled so shock waves, structural motions, electromagnetic, and thermal effects can be analyzed in a consistent manner. Smarter codes must be developed to adapt the mesh and solution techniques to optimize the accuracy without human intervention. 

In addition to specific properties of interest for a particular application of a material, its elasticity, compressive and tensile strength, deformability, hardness, wear-resistance, brittleness and cleavability also determine whether an application is possible. No matter how good the electric, magnetic, chemical or other properties are, a material is of no use if it does not fulfill mechanical requirements. These depend to a large extent on the structure and on the kind of chemical bonding. Mechanical properties usually are anisotropic, i.e. they depend on the direction of the applied force. 

Bone is mineralized tissue that constitutes part of the vertebral skeleton. Its function is to transmit and bear the loads to which the body is constantly subjected, protect the inner organs, and produce blood cells. From a mechanic point of view, the osseous tissue is an anisotropic viscoelastic material with properties that depend on direction and velocity of the applied load, as well as on the mineral content. Indeed, although the minerals confer rigidity and hardness to this tissue, the collagen imparts some elasticity, which ultimately results in its limited tensile strength and resilience. As a consequence of its composition, bone is an essentially brittle material (Fig. 17.1). Several pathologies can affect bone, including fractures, arthritis, infections, osteoporosis, and tumors, and may require adjuvant biomaterial devices. 

Properties of fiber-reinforced composites with 40-65 wt % of fiber were influenced more by fiber used than by the matrix. In contrast to an E-glass composite, which is brittle, a basalt fiber composite exhibits properties near to carbon fiber composites, except for a lower elastic modulus. Material mechanical parameters independent of sample size were calculated from flexural tests with various span-to-sample height ratios. In contrast to composites reinforced with fiber rovings, composites reinforced with fabric fiber were more brittle and less anisotropic, which was reflected in material mechanical parameters. 

Formulations of isotropic quasi-brittle materials behavior consider, generally, different inelastic criteria for tension and compression. The new model introduced in (Lourengo et al. 1997), extended to accommodate shell masonry behavior (Lourengo 2000), combines the advantages of modem plasticity concepts with a powerful representation of anisotropic material behavior, which includes different... 

The laminate composites of Carbon Fibre Reinforced Plastic (CFRP) and Carbon Fiber Reinforced Carbon (CFRC) show a very high strength and a ductile behaviour compared to brittle materials and have a low density. CFRC composites are especially suitable for high temperature applications. Therefore they are very important to aerospace technology. A single lamina of CFRP or CFRC may be considered to be homogeneous and anisotropic. The composite consists of a stack of such plies. Since each ply may have a different orientation and/or elastic moduli, the composite as a whole must be treated as an inhomogeneous anisotropic material. 

---