Design strength-related

The area of design failure criteria impacts, and is a quantitative measure of, the success of a design. Fundamentally, design failure criteria are the statement of the design requirements. The manner in which individual laminae as well as laminates fail is but a part of design failure criteria. Failure of laminae and laminates, as in Chapters 2 and 4, is a fundamental portion of all strength-related failure criteria, but those failures are also determining factors in stiffness-related failure criteria. 

Further consideration relating mechanics to joint design are given in Joint design strength and fracture perspectives, Durabiiity creep rupture. Durability subcritical debonding and Durability fatigue. 

For the best possible performance, joints should be specifically designed for adhesive bonding. In a few cases only can an adhesive be used on a joint not specifically designed for adhesives - mainly cylindrical joints. Bond stresses, materials, type of adhesive, surface preparation, methods of application and production requirements can then all be considered in relation to each other at the outset. The designer should consider especially the effect of shear, tension, cleavage and peel stresses upon the joint (Fig. 1) (see Joint design strength and fracture perspectives). 

In the case of the anchorage length, Zb, lower than the optimal length, 4. the design strength should be proportionally reduced according to the relation ... 

In the first simation, the design strength of the FRP reinforcement on the section at a distance a from the support should not exceed the value given by the expression (5.2) in the second situation, the mentioned value should be suitably deaeased according to the relation (5.4), being the maximum length available for bonding, equal to a. ... 

For effective design strength control in the case of U-wrap, the following relation can be applied ... 

Mechanical or strength-related (e.g., faulty dimensioning and design of the mould, the moulded part or the demoulding system)... 

The a—and P-aHoys are used where higher strengths are required, such as in shafts, oil and gas weUs, and medical implants. Again, Pd and Ru variations of the basic alloys are available where improved corrosion resistance is needed. Several of the Hsted P-aHoys were developed for implants. These alloys were designed to be free of aluminum and vanadium, which have created some concern related to potential toxicity when used in implants (50). 

Material strength is but one factor ia determining maximum load that can be carried by a beating material. Load capacity is equally related to design details, lubrication, and general appHcation experience. 

Fortunately the situation in practice is not quite as complex as it might seem. In general, very acceptable designs are achieved by using impact data obtained under conditions which relate as closely as possible to the service conditions. Impact strength values available in the literature may be used for the initial selection of a material on the basis of a desired level of toughness. Then, wherever possible this should be backed up by tests on the plastic article, or a specimen cut from it, to ensure that the material, as moulded, is in a satisfactory state to perform its function. 

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