Composite resin reinforced with pre-tensioned glass fibers. Influence of prestressing on flexural properties.

Objectives: This investigation evaluated the flexural properties of two composite resins, and the influence of unidirectional glass fiber reinforcements, with and without pre-tensioning.

Methods: Two composite resins (Q: Quixfil and A: Adoro) were used to fabricate 2 mm x 2 mm x 25 mm beams (N = 10), reinforced with two fiber bundles along the long axis of the beam and pre-tensioned under a load equivalent to 73.5% of its tensile strength (groups QPF and APF). In two other experimental groups, the bundles were similarly positioned but without pre-tension (groups QF and AF). Two more groups were included without fiber reinforcement (control groups Q and A). After 24h storage, specimens were subjected to a three-point flexural bending test to establish the flexural module, the deflection at initial failure and the flexural strength. Data were analyzed using a two-way analysis of variance (composite resin system and fiber reinforcement type) and the Tukey HSD post hoc tests (alpha = .05).

Results: The results showed that prestressing increased the flexural module of Adoro specimens (p<.001) but not Quixfil (p = .17). Prestressed beams reached greater deflection at initial failure than those conventionally reinforced (p<.001), namely .85-1.35 mm for Adoro and .66-.90 mm for Quixfil. Prestressing also significantly increased the flexural strength of beams (p<.001) in both Adoro and Quixfil groups, from 443.46 to 569.15 MPa and from 425.47 to 568.00 MPa, respectively.

Significance: Pre-tensioning of unidirectional glass fibers increased both deflection until initial failure and flexural strength of Quixfil and Adoro composite resins, however, with limited effects on the flexural modulus.