Strength properties of composites

Figure 7. Strength properties of composites V5. water content. A. 10° off axis test, (X) resin I, (- -) resin II, B. cross-ply specimens of resin III, (X) 0/90/0 configuration, (+) 90/0/90 configuration.

Susuki I. Static and fatigue strength properties of composite laminates under in-plane biaxial loadings. In Proceedings of 5th international conference on biaxial/multiaxial fatigue and fracture 1997. pp. 79—89. Cracow, Poland. 

The research results confirm that the application of silica-organic compounds for modification of cellulose fiber surface considerably improves strength properties of composites [50, 51, 72-75]. Raj et al. [72] found that the modification of cellulose fibers with silanes as well as with isocyanate caused improvement of mechanical properties of composites based on polypropylene matrix. However, studies conducted by Hornsby et al. [76] do not confirm that. His results prove that processing flax fibers with silanes has no effect on mechanical properties of composites based on polypropylene matrix. These contradictory conclusions are probably the effect of a complex anatomical structure of cellulose fiber and/or application of suitable conditions of modification reaction. 

Table 15. Strength Properties of Phenolic—Carbon-Fiber Composites...

Fig. 5. The immediate effect of temperature on strength properties of clear wood, expressed as percentage of value at 20°C. Trends illustrated are composites from studies on three strength properties modulus of mpture in bending, tensile strength perpendicular to grain, and compressive strength parallel to grain. VariabiUty in reported results is illustrated by the width of the bands. MC = moisture content.

However, in composites, fiber ruptures result in development of mainline cracks even at lower stresses. It is therefore necessary to know the so-called attainment coefficient in order to predict the mechanical properties of composites. The fiber strength in a PCM [Pg.20]

It should be noted that for polymerization-modified perlite the strength parameters of the composition algo go up with the increasing initial particle size. [164]. In some studies it has been shown that the filler modification effect on the mechanical properties of composites is maximum when only a portion of the filler surface is given the polymerophilic properties (cf., e.g. [166-168]). The reason lies in the specifics of the boundary layer formation in the polymer-filler systems and formation of a secondary filler network . In principle, the patchy polymerophilic behavior of the filler in relation to the matrix should also have place in the failing polymerization-modified perlite. 

Properties of composites obtained by template poly condensation of urea and formaldehyde in the presence of poly(acrylic acid) were described by Papisov et al. Products of template polycondensation obtained for 1 1 ratio of template to monomers are typical glasses, but elastic deformation up to 50% at 90°C is quite remarkable. This behavior is quite different from composites polyacrylic acid-urea-formaldehyde polymer obtained by conventional methods. Introduction of polyacrylic acid to the reacting system of urea-formaldehyde, even in a very small quantity (2-5%) leads to fibrilization of the product structure. Materials obtained have a high compressive strength (30-100 kg/cm ). Further polycondensation of the excess of urea and formaldehyde results in fibrillar structure composites. Structure and properties of such composites can be widely varied by changes in initial composition and reaction conditions. 

The interaction of two substrates, the bond strength of adhesives are frequently measured by the peel test [76]. The results can often be related to the reversible work of adhesion. Due to its physical nature such a measurement is impossible to carry out for particulate filled polymers. Even interfacial shear strength widely applied for the characterization of matrix/fiber adhesion cannot be used in particulate filled polymers. Interfacial adhesion of the components is usually deduced indirectly from the mechanical properties of composites with the help of models describing composition dependence. Such models must also take into account interfacial interactions. 

For typical filament winding applications, the fiber reinforcement provides the stiffness and strength required to maintain structural integrity. Thus, material characterization for filament wound structures focuses on characterizing the fiber dominated stiffness and strength properties of the composite. The stiffness of fiber reinforced plastics (FRPs), in the fiber direction, is dominated by the fiber stiffness characteristics. The strength will be influenced by a number of factors, however, and not all of them are related to the fiber, including ... 

Flexural properties in the 0° direction are largely determined by the fiber properties however, the matrix/interphase may also control the failure mode or path which may in turn affect the strength properties of the composite. The 0° flexural properties of the composites made with bare and sized E-glass are listed in Table 7. 

It thus appears that there may be a basis for some predictions which can guide in the selection of components for composite materials, but the theoretical basis for discussions goes always back to the principles of the volcano curve in the sense that a relative increase or decrease in activity is customarily explained by recurring to the features of such a curve [92], Therefore, a theory is needed to describe the dependence of the adsorption strength of hydrogen on the electronic properties of composite materials. However, before a sound theory can be proposed, it is necessary that the experimental picture be freed from the many obscurities, ambiguities and irreproducibilities due to the scarce characterization of the surface of various materials, and to the insufficient identification of various factors which can influence electrode kinetics. 

The strength properties of fibers are statistical in nature. Consequently, it is necessary to apply principles of weakest link statistics, which define the properties of fibers within a composite. The initial decision to be made concerns the potential for interactions between failed fibers and matrix cracks. It has generally been assumed that matrix cracks and fiber failure are noninteracting and that global load sharing (GLS) conditions are obtained .16,63,64 In this case, the stress along a material plane that intersects a failed fiber is equally distributed among all of the intact fibers. Experience has indicated that these assumptions are essentially valid for a variety of CMCs. 

In this section, a new type of structural panel manufactured with a combination of these two wood resources is discussed. Waste wood chips were processed to particle and used as a core material. Small diameter logs were cut by a disk flaker to produce wafer or strand , which was used in Wafer-board or OSB production in North America. These strands were used as face layers of three-layer structural board in this experiment. Strength properties of the composite board made from Sugi-strand and recycled wood particle were evaluated. 

Table 1 Interlaminar shear strength properties of phenolic composites...

---