title: Influence of thermal cycling on flexural properties of composites reinforced with unidirectional silica-glass fibers.
abstract: OBJECTIVE
  The purpose was to investigate the effect of water storage and thermal cycling on the flexural properties of differently sized unidirectional fiber-reinforced composites (FRCs) containing different quantities of fibers. The effect of fiber orientation on the thermal expansion of FRCs as well as how the stresses in the composites can be affected was considered.
  
  
  METHODS
  An experimental polymeric base material was reinforced with silica-glass fibers. The cleaned and silanized fibers were sized with either linear PBMA-size or crosslinked PMMA-size. For the determination of flexural properties and water uptake, specimens were processed with various quantities of differently sized unidirectional fibers. Water uptake of FRC was measured. Water immersed specimens were thermally cycled for 500 and 12,000 cycles (5 degrees C/55 degrees C). Flexural properties of "dry" and wet specimens with and without thermal cycling were determined by a three-point bending test. The linear coefficients of thermal expansion (LCTE) for FRC samples with different fiber orientations were determined using a thermomechanical analyzer.
  
  
  RESULTS
  Water uptake of the FRC specimens increased with a decrease in fiber content of the FRC. Flexural properties of FRCs improved with increasing fiber content, whereas the flexural properties were not influenced significantly by water and thermal cycling. Fiber orientation had different effects on LCTE of FRCs. Unidirectional FRCs had two different LCTE in longitudinal and transverse directions whereas bidirectional FRCs had similar LCTE in two directions and a higher one in the third direction.
  
  
  CONCLUSIONS
  The results of the study suggest that the surface-treated unidirectional silica-glass FRC can be used for long-term clinical applications in the oral cavity.
authors.affiliation: Department of Prosthetic Dentistry, Institute of Clinical Dentistry, University of Oslo, Oslo, Norway.
authors.forename: Gökçe
authors.initials: G
authors.lastname: Meriç
authors.forename: I Eystein
authors.initials: IE
authors.lastname: Ruyter
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D005026:Ethylene Glycols / Q000737:chemistry; D005898:Glass / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D020366:Methylmethacrylate / Q000737:chemistry; D018583:Pliability; D011109:Polymethacrylic Acids / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003432:Cross-Linking Reagents; D003764:Dental Materials; D005026:Ethylene Glycols; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011145:Polyvinyls; D014867:Water; D020366:Methylmethacrylate; C024546:diethylene glycol dimethacrylate polymer; D012822:Silicon Dioxide; C003080:poly(vinyl chloride)-poly(vinyl acetate) copolymer; C068872:polybutyl methacrylate; D019904:Polymethyl Methacrylate; C102737:1,4-butanediol dimethacrylate; C016284:butyl methacrylate