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Browsing by Subject "Flexural strength"
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Item Flexural strength comparison of monolayer resin composite to bilayer resin/ liner composite(2009) Azzam, Mai; Platt, Jeffrey A.; Levon, John; Taskonak, Burak; Brown, David; Andres, Carl; Legan, JosephClinical evidence suggests that the use of liners in posterior composite restorations may increase the frequency of restoration fractures. Materials that have been used as liner materials for resin composite (RC) restoration include conventional glass ionomers, resin-modified glass ionomers (RMGI), and flowable composites. The aim of this study was to compare the flexural strength of a monolayer of resin composite with that of a bilayer of resin composite and liner. Four types of RC beams were tested: a monolayer control that is an un-lined RC (Tetric EvoCeram, Ivoclar Vivadent) and three “bilayer” specimens that consisted of this same RC lined with one of three liners. The three liners used included two RMGI cements (Vitrebond LC liner; 3M ESPE and, GC Fuji Lining LC; GC America) and a flowable resin composite (Tetric EvoFlow, Ivoclar Vivadent). Each group was tested after water storage for 24 h and 30 d. Altogether, eight, 12-specimen groups were fabricated and tested. Methods: A 25 x 2 x 2 mm mold was completely filled with the RC to form the control beams. To form the bilayer beams, this mold was filled with 0.5 mm of the liner and then with 1.5 mm of the RC. Specimens were stored in 37oC distilled for either 24 h or 30 d. Immediately prior to testing, the 30-day groups were also thermocycled 2500 times, between water baths at 7 oC and 48oC with a 30-s dwell time and a 10-s transit time. Flexural strength was determined using a three-point–bending device. A twoway analysis of variance (ANOVA) with interactions was used to investigate how liner group (or no liner) and storage time affected strength. Results: The interaction between liner type and storage time was significant (p = 0.0128). The un-lined RC (the monolayer beam) was significantly stronger after 24 h than after 30 d in water (p = 0.0098). Water storage between 24 h and 30 d did not change the flexural strength of any of the bilayer (lined) beams (p > 0.05). After storage for 24 h and also for storage for 30 d, both un-lined RC and RC lined with the flowable RC exhibited significantly higher flexural strength (p = 0.0001) than the bilayer beams lined with either RMGI liners.Item Short- and Long-Term Structural Characterization of Cured-in-Place Pipe Liner with Reinforced Glass Fiber Material(MDPI, 2020-03) Ji, Hyon Wook; Koo, Dan Daehyun; Kang, Jeong-Hee; Engineering Technology, School of Engineering and TechnologyCured-in-place pipe (CIPP), as a kind of trenchless sewer rehabilitation technology, is a method to repair sewer pipe using unsaturated polyester resin. This study develops a CIPP liner using hot water or steam curing as well as glass fiber, in contrast to traditional methods, which use nonwoven fabric. Composite material samples were fabricated by combining liner materials using various methods, and the structural characteristics of the liners were compared and analyzed through short- and long-term flexural strength tests. A long-term test was conducted for 10,000 h, and the results revealed 13.3 times higher flexural strength and 8 times higher flexural modulus than the American Society for Testing Materials minimum criteria for CIPP short-term properties. The maximum creep retention factor was 0.64, thereby reducing the design thickness of the CIPP by up to 54%. The structural characteristics also improved when glass fibers were mixed with traditional CIPP liner, making it possible to reduce the thickness by 30%. Glass fibers result in high structural strength when combined with unsaturated polyester resin. Structural strength increased, even when glass fibers were mixed with traditional CIPP liner. The main contribution of this research is the development of a high strength CIPP liner and improvement of the structural properties of CIPP lining without using the specially formulated resin or lining materials.