Mechanical properties long-term

Thermoplastics and Thermoplastic Composites 3.1.5 Long-term mechanical properties... 

Physical aging in the epoxy matrix definitely affects the long-term mechanical properties of the composite. As the material was further sub-Tg annealed at 140 °C for 102, 103, 104, and up to 105 minutes, the toughness and other ultimate properties... 

The advent of high-strength carbon-based fibers has led to a number of structural applications in medical treatment. The specifications for implanted materials required that they offer acceptable long-term mechanical properties and surfaces that are biocompatible [126]. Surface compatibility affects immediate acceptance, while the long-term mechanical performance is determined by the bulk properties of the implant. 

Porter [212] applied his group interaction modeling approach to both the nonlinear strain and the long-term mechanical properties of polymers. He showed that both problems can be explained qualitatively by his concept of discrete energy levels in a polymer. His key argument is that a fraction of rubberlike states coexists with the predominantly glassy state of a polymer below Tg is a function of the temperature, time and mechanical energy of deformation and... 

The correspondence principles allow us to achieve our goal prediction of long-term mechanical properties—and thus performance and reliability—from short-term tests. It is possible to predict behavior for, say, 16 decades of time from experiments each of which was made over four decades only examples will be given below. It is easy to see that, when using the time-temperature correspondence, essential is the capability to predict the temperature shift factor ariT). Similarly, when using the time-stress correspondence one needs the stress shift factor ao-ia). Starting from the Doolittle equation (24.8), it was possible to obtain a general equation [26]... 

Xanthos and co-workers [12] did some research in which LDPE was melt blended with either automotive shredder residue, carpet hacking residue or mixtures of the two and prototype blocks were intrusion moulded from them. These blocks were evaluated for use as a wood substitute for the building industry by conducting tests to determine their short-term and long-term mechanical properties, flammability, thermal conductivity and heavy metal and total organic carbon leaching behaviour. The performance of these prototypes was compared with that of wood and the composites containing carpet residue were found to be favourable as replacements for wood thermal barrier components in a steel-based stud assembly. 

Based on this work on aromatic polyesters, Schnell et al. [30] and Fox [31] independently prepared hnear, bigh-melting, bigh-molecular-weight aromatic polycarbonates in 1953—1954 that were derived from 4,4 -dihydroxy-diphenylalkane monomers. These aromatic polycarbonates could be prepared either (1) by a two-phase interfacial method (a modified Schotten-Baumann reaction) or (2) by a melt transesterification (monomers-as-solvent) process using diphenyl carbonate [32]. Versus earher aUphatic polycarbonates, the aromatic polycarbonates were unique in tbat they could be made into water-clear (colorless) transparent structures tbat possessed excellent long-term mechanical properties. 

This report represents the first to recognize the effects of this non-equilibrium behavior in epoxy glasses on the long-term mechanical properties of graphite/epoxy composites. This finding is particularly important in view of the growing applications of graphite/epoxy composites as structural parts in aerospace and automotive industries. 

Table 3.1-73 Long-term mechanical properties of heat-resistant steels bands...

Load. Creep and stress relaxation measurements can determine the long-term mechanical properties of materials and their ability to withstand loading and deformation influences. 

There are several standards dealing with creep and long-term mechanical properties. 

PE-1 was slightly higher than that of PE-2, but the opposite situation occurred in the high temperature fractions of these two samples. It was demonstrated that lower the content of comonomer in the low MW parts and increase the content of comonomer in the high MW parts would be crucial in order to achieve much better long-term mechanical properties of the HDPE pipe materials. 

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