Glass fiber elastic behavior

The Clock Spring composite laminate layers are nominally 0.065 in. thick and have a glass fiber content ranging from 60 to 70 percent by weight (45 to 55 percent by volume). The Clock Spring composite material exhibits linear elastic behavior up to the point of failure in tension, typically 1.5—2% strain. Typical values of the elastic modulus are 5 X 10 psi in the fiber direction and 1.4 x 10 psi in the transverse direction. Tensile strength is typically 75 to 100 ksi. The coefficient of thermal expansion is 6.0 X 10 in./in./°F in the fiber direction and 3.2 x 10 in./in./°F in the transverse direction (see [4] in sources of further information). 

Similar to the situation with 2D membranes, the basic molecular characteristics of chitosan such as DD also show great influence on the ability of chitosan scaffolds to modulate stem cell behavior. The chitosan scaffolds with a high DD can maintain the viability and pluripotency of buffalo embryonic stem-like (ES-Uke) cells [15]. However, the cell behavior on 2D and 3D environments are quite different. Comparison of MSC behavior in both 2D plates and chitosan/gelatin/chondroitin scaffolds demonstrates that the 3D microenviromnent can enhance osteogenesis and maintain the viability of cells [161]. The research by Altman et al. [162] found that the apparent elastic modulus and cytoskeleton F-actin fiber density were higher for ADSCs seeded in 3D sflk fibroin/chitosan scaffolds than on 2D glass plates (Fig. 13). 

Polymers come in many forms including plastics, rubber, and fibers. Plastics are stiffer than rubber, yet have reduced low-temperature properties. Generally, a plastic differs from a rubbery material due to the location of its glass transition temperature Tg). A plastic has a Tg above room temperature, while a rubber will have a Tg below room temperature. Tg is most clearly defined by evaluating the classic relationship of elastic modulus to temperature for polymers as presented in Fig. 1.1. At low temperatures, the material can best be described as a glassy solid. It has a high modulus and behavior in this state is characterized ideally as a purely elastic sohd. In this temperature regime, materials most closely obey Hooke s law ... 

---