Composition strength requirements

The choice of composition of a semi-gelatine depends ultimately on two requirements, namely the strength required and the resistance to water needed for the particular application. For economic reasons the lowest nitroglycerine content which satisfies both these requirements is always chosen. 

Flexural strength and flexural modulus are being used as the screening criteria for a new ADA specification 27 which adopts the new ISO standards. The minimum flexural strength required will be 50 MPa. In addition, the criterion makes it mandatory that the flexural strength must exceed a value, N, based on the flexural modulus, where N = (flexural modulus 0.0025) + 40. This stipulation will require higher flexural moduli from the stiffer composites like the conventional, small particle and hybrid systems. 

In pultrusion of composites with all the reinforcement axially aligned, the pre- and postimpregnation guidance is quite straightforward. In contrast, to place mats, fabrics, and veils corrrectly to form an intricate, thin-walled, and hollow cross-section, such as a window profile, considerable ingenuity, skill, and experience are required. From a composite strength... 

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 ... 

The mechanical response of composites, as shown in these exploratory studies, indicates dependence on the ease with which fracture can occur between fibers, yarns, and plies. Poorly crystallized matrices result in composites that are strong and stiff but with little yield so that failure occurs catastrophically. In contrast, more crystalline matrices seem to be not quite as strong and to have a lower effective modulus, but their increased strain capability ensures that failure is not catastrophic the composited strength decays gradually as further strain is applied. Thus, the energy required for total failure is increased, and the composite with more crystalline matrix is more tolerant of defects or stress risers. 

It will be noted that the compressive strength requirements of the three classes of hydraulic limes overlap. This is to accommodate variations caused by changes in the composition of the limestone and in the calcining process (in the case of natural hydraulic limes) and by variations in the components of artificial hydraulic limes. 

For general use, i. e. when the environment has a mild aggressiveness and the strength requirements for concrete are in the usual range, most cements can be suitable. In that case the selection is made on the basis of cost or local availabihty. Portland and Portland-composite cements with strength class 32.5 or 42.5 are nowadays available as general-purpose cements. Although in several European countries Pordand-limestone cements can be found (Table 1.3), cements blended... 

Evaluation of the composition, strength, and Charpy V-notch (CVN) impact toughness of the base plate and weldments was conducted using selected U. S. code and regulatory body requirements. Base plate data are summarized in Table I and weldment data in Table II. 

---