title: The influence of short-term water storage on the flexural properties of unidirectional glass fiber-reinforced composites.
abstract: OBJECTIVE
  The aim of this study was to determine flexural properties of unidirectional E-glass fiber-reinforced composite (FRC) with polymer matrices of different water sorption properties.
  
  
  METHODS
  Rhombic polymer and FRC test specimens made of three commercially available diacrylate resin (Sinfony Activator, Triad Gel, 3M Scotchbond Adhesive) and different volume fractions of fibers were tested with three-point bending test according to ISO 10477 after storing in water for 30 days. Water sorption of specimens was also measured.
  
  
  RESULTS
  Flexural strength of specimens with 45 vol% fraction E-glass fibers varied from 759 to 916 MPa in dry conditions. Water-stored specimens showed flexural strengths of 420-607 MPa. ANOVA analysis revealed that the fiber-volume fraction and the water sorption of the polymer matrix had a significant effect (p < 0.001) on the flexural properties. Dehydration of specimens recovered the mechanical properties. Decrease of flexural properties after water immersion was considered to be mainly caused by the plasticizing effect of water and the decrease depended on water sorption.
  
  
  CONCLUSIONS
  Use of polymers with low-water sorption seems to be beneficial in order to optimize the flexural properties of FRC.
authors.affiliation: Institute of Dentistry and Biomaterials Research, University of Turku, Finland. lippo.lassila@utu.fi
authors.forename: L V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: T
authors.initials: T
authors.lastname: Nohrström
authors.forename: P K
authors.initials: PK
authors.lastname: Vallittu
mesh_terms: D000042:Absorption; D003188:Composite Resins / Q000737:chemistry*; D005898:Glass / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011108:Polymers / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D011108:Polymers; D019279:Resin Cements; D014867:Water