Flexural properties of fiber reinforced composite using a vacuum/pressure or a manual adaptation manufacturing process

Purpose: This study investigated the influence of fiber content and water s torage on the flexural strength of beams made of two fiber-reinforced compo sites (FRC), the Vectris and the FibreKor system. Material and methods: A manual adaptation method (FibreKor, n = 30) and a v acuum/pressure process (Vectris, n = 30) were compared using 25 x 4 x 2 mm( 3) beams. One group of the Vectris (n = 10) and the FibreKor beams (n = 10) was stored in water for 24 h, a further group was thermal-cycled (TC) 6000 x 5 degrees C/55 degrees C, and a third group was stored in water for 30 d ays at 37 degrees C. All beams were then loaded to failure using a three-po int bending test and the flexural strength was calculated. Finally, the fib er volume percent (vol%) was determined. Results: Generally, the flexural strength decreased significantly with incr easing storage time independent of the investigated fiber- and/or manufactu ring system. With the parameters 24 h/TC/30 days, the mean of flexural stre ngth for the Vectris beams was 618/579/545 N/mm(2), and for FibreKor 585/53 4/499 N/mm(2). A fiber content of 28.1 +/- 0.4 vol% was assessed for the Ve ctris beams and 12.8 +/- 0.6 vol% for the FibreKor beams. After 24 h storag e in water, the Vectris and the FibreKor beams demonstrated a statistically significant higher flexural strength than after 30 days storage in water. Conclusions: A vacuum/pressure manufacturing process in contrast to manual adaptation, resulted in a markedly higher fiber content, but did not necess arily lead to significantly higher flexural strength. Not only the fiber co ntent, but also matrix composition as well as the bond between fibers and m atrix determined the properties of FRC. (C) 2000 Elsevier Science Ltd. All rights reserved.