ABSTRACT
The properties of polymers span a very broad range, from viscous fluids, to rubber, and to hard solids. In the field of biomaterials, polymers as implants or medical devices have found wide application in treating patients with tissue loss and organ failure. Yet one of the major drawbacks of polymeric biomaterials is that their mechanical properties may not be sufficient for high load-bearing applications, such as in orthopedics, if these materials are compared with metallic implants, which
have a very high stiffness and strength. However, when implants made of metals are used in the body, it may lead to a phenomenon called the stress-shielding effect because of the mismatch between the modulus of the implants and the surrounding tissues. Furthermore, metal alloys may be subject to corrosion in the biological environment. As a result, there have been tremendous efforts in the past few decades to improve the stiffness and toughness of polymers so that their properties match those of hard tissue. One practical way to do so is to introduce into a polymer matrix a reinforcing phase of high strength and modulus to produce a composite material. Compared with metals and ceramics, the polymer-based composite materials are less stiff, have high fatigue strength, and their properties and structures can be easily tailored to meet specific requirements.
