Strength of PMMA Reinforced with Acid-Etched Polyaramid fibers

Previous studies have demonstrated that treating the fiber surface could improve the bonding between the fiber and the matrix and hence, increased the strength of the composite. Objectives: To determine the transverse and impact strengths of polymethyl methacrylate (PMMA) reinforced with acid-etched polyaramid fibers. Methods: Two sets of five groups of heat-polymerized PMMA specimens (n = 10/group) were prepared for transverse and impact strength testings as follows: (1) no fiber reinforcement, (2) reinforced with 2% by wt of unetched polyaramid fibers, and (3)-(5) reinforced with 2% by wt of 1%, 10% and 35% phosphoric acid etched polyaramid fibers. The fibers were placed longitudinally in the middle of PMMA specimen. All specimens were immersed in distilled water at 37°C for 14 days prior to testing. The Kruskal-Wallis test at the 95% confidence level was used to analyze the results. The fractured characteristic of the reinforced specimens was also investigated under a scanning electron microscope. Results: The transverse strength of unreinforced specimens (55.30±4.14MPa), specimens reinforced with unetched fibers (67.68±1.27MPa), and specimens reinforced with acid-etched fibers (69.78±2.24MPa to 71.25±1.59MPa) were significantly different. There was also a statistically significant difference in impact strength between unreinforced specimens (0.44 ftlb/in) and reinforced specimens (6.94 ftlb/in). However, there was no difference among the reinforcement groups (groups 2 to 5). Conclusions: Pretreatment of polyaramid fibers with 1 to 35% phosphoric acid slightly improved the transverse strength of polyaramid fibers reinforced PMMA but had no effect on the impact strength. (This study was supported by funding from Graduate school, Prince of Songkla University.)