Effect of Fiber Penetration into Veneer Region of Bi-Layer Beams

Objective: To test fiber reinforced composite (FRC) substructure arrangements within a bi-layer beam on the load to initial (IF) and final failure (FF) in a mode II delamination test. Methods: Three groups of FRC and particulate reinforced composite (PRC) were tested: PE (Ultra high molecular weight polyethylene ribbon (Connect) and BelleGlass, Kerr), W (woven E-glass (Vectris Frame) and Targis, Ivoclar), and U (unidirectional R-glass (Vectris Pontic) and Targis, Ivoclar). Twelve specimens were fabricated by placing an FRC layer into 25 x 6 x 0.75 mm³ mold. PRC (10mm x 0.75mm) was added to the specimen center. The FRC was placed into unpolymerized PRC layer at 3 depths to the veneer surface: 0%, 50%, or 100%. After light-polymerization, the specimens were standardized and measured by digital caliper, then stored 1 week in 37^oC water. Four specimens were randomly selected for sectioning/pre-test evaluation. The remaining 8 specimen (=n) were loaded in a static 4-point bend test (20mm upper/ 10mm lowers spans) veneer side down until failure (recording IF and FF). A fracture ratio (FR) was developed (IF/FF x 100). Results: Means and standard deviations (SD) were calculated (within fiber groups, same letter are not statistically different: ANOVA, Tukey post hoc, p< 0.05). Conclusion: Glass fiber positions with 50% penetration into the PRC significantly increased the load to IF.