O papel das fibras e qualidade da matriz em resinas compostas de alto desempenho

Abstract

Conventional particulate-filler composites (PFCs) exhibit low fracture toughness (KIC), limiting their longevity. Short fiber-reinforced composites (SFRCs) overcome this brittleness, but controversy exists whether fiber architecture (aspect ratio) or polymer matrix quality is the dominant factor for toughness. This study aimed to critically evaluate four commercial SFRCs (two packable: EverX Posterior, ThinkX; and two flowable: EverX Flow, ThinkX Flow) and two PFCs (Gradia Direct Anterior, G-aenial Universal Flo) to correlate mechanical performance with fiber architecture and matrix composition. Fracture toughness (KIC), flexural strength (FS), and flexural modulus (FM) were determined (n=10) according to ASTM D5045 (SENB) and ISO 4049 (threepoint bending), respectively. Data were statistically analyzed using one-way ANOVA and Tukey's test (p<0.05). All SFRCs exhibited significantly higher KIC than PFCs (p<0.05). The flowable SFRCs showed the highest toughness, with ThinkX Flow (4.18 MPa·m¹/² being statistically superior to all other materials, followed by EverX Flow (3.62 MPa·m¹/²). The packable SFRCs (EverX Posterior and ThinkX) did not differ from each other (2.78 and 2.87 MPa·m¹/², respectively). EverX Posterior recorded the highest FS (156.62 MPa). It was concluded that achieving a sufficient fiber aspect ratio (e.g., >20) combined with a high fiber concentration (volume fraction) were more dominant factors for increasing toughness than achieving a "critical" fiber length. Furthermore, when concentration is similar, matrix quality and interfacial optimization become the critical determinants.