| Summary: | 碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 104 === The tensile and bearing strength of notched composites is an important factor for composite structural design. However, no literature is available on the notch sensitivity and pin loaded effects of self-reinforced polymer composites. In this study, self-reinforced recycled poly (ethylene terephthalate) (srrPET) composites were produced by film stacking from fabrics composed of double covered uncommingled yarns (DCUYs). Composites specimens were subjected to uniaxial tensile, flexural and Izod impact tests and the related results compared with earlier ones achieved on srPET composites reinforced with non-recycled technical PET fibers. Further on, the effects of open circular holes on the tensile strength of srrPETs with various width-to-hole diameter (W/D) ratios of the specimens, the effects of pin-loaded tensile behavior of srrPET composites with various W/D ratios and edge distance-to-hole diameter (E/D) ratios of the specimens, the endurance limit of tension–tension fatigue of pin loaded composites and damage development in srrPETs assessed by located acoustic emission were studied.
Damage development in srrPET composites indicates that srrPET composites have higher resistance of the composite to crack propagation. These results proved that srrPET composites is tough, ductile notch-insensitive materials and have superior load carrying capability.
The experimental results indicate that the bilinear (yielding followed by post-yield hardening) stress-strain curves were recorded in the open hole tensile (OHT) measurements. The srrPET composites had extremely high yield strength retention (up to 142%) and high breaking strength retention (up to 81%) due to the superior ductile nature of the srrPET composites, which induces plastic yielding near the hole thereby reducing the stress concentration effect. The superior load carrying capability is found in srrPET composites and highly dependent on the W/D ratios. The bearing failure mode occurs in W/D>4, the composites has high yield bearing strength (99.4 MPa) and extremely high ultimate bearing strength (199.3 MPa) due to strong interfacial bonding between the fiber and matrix contributes higher bearing strength. The strong interfacial bonding in srrPET composites has higher fatigue cycles and shows good endurance ability.
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