Epoxy creep behavior

Creep Behavior of Amine-Cured Epoxy Networks Effect of Stoichiometry... 

Ducept et al., [13] studied mixed mode failure criteria for a glass/epoxy composite and an adhesively bonded composite joint. In their study, the initiation failure point detected by acoustic signal and by the non-linearity point on the load/displacement curve and found good correspondence. Magalhaes et al., [14] studied the application of acoustic emission to investigate the creep behavior of composite bonded lap shear joints. 

Among the available scientific literatme on the creep response of PNCs [15-43], the majority of papers are focused on the effect of 1-D layered nanofillers of the creep behavior of polymers such as poly (ethylene oxide) (PEO) [15], poly (ethylene terephthalate) (PET) [18], ethylene propylene rubber (EPR) [17], polypropylene [24], nyloii-66 (PA66) [19], nylou-6 (PAG) [22,23], high density polyethylene (HDPE) [21,38,44], poly(ethylene-co-acryhc acid) copolymer [26], epoxy resin (EP) [28], polystyrene (PS) [29], polymethane (PU) [30], and polystyrene-6/oc/5-polybutadiene-6ZocAvpolystyrene triblock copolymer (SBS) [37]. 

Water is a natural plasticizer for many polar polymers such as the nylons (23K). polyester resins (239), and cellulosic polymers (240). It strongly shifts in epoxies (241.242). Thus the creep and stress-relaxation behavior of such polymers can be strongly dependent on the relative humidity or the atmosphere. 

In some epoxy systems ( 1, ), it has been shown that, as expected, creep and stress relaxation depend on the stoichiometry and degree of cure. The time-temperature superposition principle ( 3) has been applied successfully to creep and relaxation behavior in some epoxies (4-6)as well as to other mechanical properties (5-7). More recently, Kitoh and Suzuki ( ) showed that the Williams-Landel-Ferry (WLF) equation (3 ) was applicable to networks (with equivalence of functional groups) based on nineteen-carbon aliphatic segments between crosslinks but not to tighter networks such as those based on bisphenol-A-type prepolymers cured with m-phenylene diamine. Relaxation in the latter resin followed an Arrhenius-type equation. 

The increase of the glass-transition temperature and the decrease of creep of epo3 polymers with 10% SKD-KTRA demonstrate the effect of the rubber upon the epoxy matrix itself. Such abnormal behavior of EEC can be explained thermodynamically. An SKD-KTRA content of 10% in ERG ensures thermodynamic conditions for separation of the... 

Hiel has used both the TSSP and the Schapery procedure to produce master curves of the shear behavior of a carbon epoxy composite. An example of his results is given in Fig. 10.15. The shear creep compliance of a carbon epoxy composite is shown for various stress levels. The data were shifted horizontally to form a smooth master curve for the lowest stress level as illustrated by the open symbols. The Schapery procedure was also used independently on this data set and the resulting master curve prediction is indicated by the solid line. For more details, see the cited reference in Fig. 10.15. 

Typical interior holding adhesive applications are listed in Table 2. One of their major functions is to retain vinyl or ABS films against interior door or sidewall trim panels. The ABS or vinyl sheet material is often vacuum drawn into recesses in the door or trim panel. It may have a tendency to pop loose and creep away from concavities or from the backside of the panels. This behavior, which may be expected whenever the sheet material is under tension, is overcome by the use of adhesives such as epoxies which do not cold flow and which begin to cure when heated in the vacuum forming operation. For panels where there is less tension on the sheet material, hot melts or solvent cements may be used. An example is the use of a hot melt hemming adhesive to secure plastic sheet when it is wrapped over the edge of a door or trim panel. 

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