Bending and stiffness

Cord materials such as nylon, polyester, and steel wire conventionally used in tires are twisted and therefore exhibit a nonlinear stress—strain relationship. The cord is twisted to provide reduced bending stiffness and achieve high fatigue performance for cord—mbber composite stmcture. The detrimental effect of cord twist is reduced tensile strength. Analytical studies on the deformation of twisted cords and steel wire cables are available (22,56—59). The tensile modulus E of the twisted cord having diameter D and pitchp is expressed as follows (60) ... 

We usually must go beyond the simple concept of a monocoque or single-thickness skin for whatever structure we design. That is, we must usually consider the bending stiffness, and, to achieve structural efficiency, we often must stiffen a structure in some manner. We will first address the terminology of stiffening and how it is used. Then, we will consider the types of stiffeners that could be used. Next, an important issue that arises in the design of stiffeners is whether the stiffener has an open- or a closed-cross section. Then, we will address some of the... 

For charged polymers, the effective bending stiffness and thus the Kuhn length is increased due to electrostatic repulsion between monomers [30-36]. This effect modifies considerably not only the PE behavior in solution but also their adsorption characteristics [37]. 

The mechanics analysis of the forces on the climber s body (Smith, 1998) assumes that the rope has negligible bending stiffness, and that a length L of rope has a linear force P versus extension x relationship with slope (tensile stiffness) Pl (Nm ). We see later (Fig. 15.7) that this is a reasonable approximation. The rope tensile parameter k is defined as the product of a rope s tensile stiffness and its length... 

A computer program has been written and used to caleulate a solution for an aramid rope subject to tension-tension cycling at 38 24% of break load. Although there is uncertainty in the values chosen for the defining parameters, particularly the bending stiffness and plastic moment of the yarn, the predictions were of the same order of magnitude as the examples of failures in ropes, which are shown in Fig. 19. 

Tv2 being outside the time scale represented, the values of bending stiffness and Kb, and the number of cycles (milhon) corresponding to this point are noted separately in the hgures. 

FE model of a fabric sample compressed from each side with (a) high bending stiffness and with (b) low bending stiffness. 

Fig. 10 The relationship between (a) tensile index, i.e. the stress at break, and sheet density and (b) bending stiffness and tensile index for all the pulps studied in Gardlund et al. [54]...

Neat PLA polymer suffers from the limitations of low bending stiffness and shear strength and is not sufficient for... 

An important function of the GDL is to even out the compression forces in the stack. These compression forces are also a source for degradation. Lee and Merida concluded from ex situ experiments that the compressive strain increased with the applied pressure but even more strongly with temperature, and the GDL strain was influenced by the PTFE stability [158]. Properties such as in-plane electrical resistivity, surface contact angle, bending stiffness, and porosity were not affected. However, it was found that convective airflow through the GDL under strain can lead to loss of material. The GDL degradation can also contribute to sudden failure as GDL fibers can puncture the membrane, either when as a result of degradation they do not distribute the compression forces well any more or when they are even broken themselves. 

Since HDPE is nearly a linear polymer it has a higher density of 0.94-0.96 g/cm the melting point of 133-138°C as well as improved tensile strength, bending stiffness and chemical resistance. 

The predicted panel bending stiffnesses and resonant frequencies for the two panels are tabulated in Table A-7 for a simply supported panel 4 m wide by 2.5 m high. The values for a fiat panel of the same overall dimensions have also been... 

---