بهبود چقرمگی شکست نانوکامپوزیت اپوکسی با استفاده هم‌زمان از نانوذرات سیلیکا با اندازه‌های مختلف

نوع مقاله: پژوهشی

نویسندگان

تهران، دانشگاه صنعتی مالک اشتر، پژوهشکده مهندسی کامپوزیت، صندوق پستی 1774-15875

چکیده

برای افزایش چقرمگی شکست کامپوزیت اپوکسی، رزین اپوکسی و سخت‌کننده انیدریدی با نانوذرات سیلیکا تقویت شد. ذرات سیلیکا با اندازه‌های 12، 20 و 40 نانومتر به شکل تنها یا ترکیب دوتایی به رزین اضافه شده و با دستگاه فراصوتی در ماتریس اپوکسی پخش شدند. تصاویر میکروسکوپ الکترونی نشان داد، پخش ذرات به‌خوبی انجام شده است. نتایج آزمون کشش، افزایش مدول یانگ و استحکام کششی کامپوزیت‌ها را با افزایش کسر وزنی ذرات تقویت‌کننده یا کاهش اندازه آن‌ها نشان داد. استفاده هم‌زمان از دو نوع ذره سیلیکا با اندازه‌های مختلف 20 و 40 نانومتر موجب ارتقای بهتر مدول یانگ و استحکام شد. اما، استفاده از ترکیب هر یک از آن‌ها با اندازه ذرات 12 نانومتر افزایش چشمگیری را در خواص کششی موجب نشد. در حالی که نتایج آزمون خمش سه‌نقطه‌ای نمونه برش‌دار، که برای اندازه‌گیری انرژی شکست انجام شد، اثر هم‌افزایی قابل توجهی را در استفاده هم‌زمان از دو نوع نانوذره سیلیکا نشان داد. انرژی شکست اپوکسی بدون نانوذرات از 280J/m2، برای کامپوزیت دارای نانوذرات  12 نانومتر تا 740J/m2 افزایش داشت. اگر این ذرات به همراه ذرات 20 نانومتر استفاده شوند، با کسر وزنی کل برابر، انرژی شکست تا 770J/m2 زیاد می‌شود. در نهایت محاسبات نشان داد، اندازه دهانه ترک حدود چند میکرومتر بوده که خیلی بزرگ‌تر از ابعاد ذرات سیلیکاست. بنابراین، نقش سازوکار‌های اتصال ترک و انحراف ترک در افزایش چقرمگی ناچیز است و تغییرشکل پلاستیک و گسترش حباب سازوکار‌‌های غالب هستند.

کلیدواژه‌ها


عنوان مقاله [English]

Improving Fracture Toughness of Epoxy Nanocomposites by Silica Nanoparticles

نویسندگان [English]

  • Seyed Reza Akherati Sany
  • Mehrzad Mortezaei
  • Iraj Amiri Amraei
Composite Engineering Research Center, Malek-e-Ashtar University of Technology, P.O. Box: 15875-1774, Tehran, Iran
چکیده [English]

An epoxy resin was modified by silica nanoparticles and cured with an anhydride. The particles with different batches of 12, 20, and 40 nm sizes were each distributed into the epoxy resin ultrasonically. Electron microscopy images showed that the silica particles were well dispersed throughout the resin. Tensile test results showed that Young’s modulus and tensile strength increased with the volume fraction and surface area of the silica particles. The simultaneous use of two average sizes of 20 and 40 nm diameter silica particles still increased these mechanical properties but other combinations of silica particles were unsuccessful. A three-point bending test on each pre-cracked specimen was performed to measure the mode I fracture toughness energy. The fracture energy increased from 283 J/m2 for the unmodified epoxy to about 740 J/m2 for the epoxy with 4.5 wt% of 12 nm diameter silica nanoparticles. The fracture energy of smaller particles was greater because of their higher surface to volume ratio. The fracture energy results showed also that the combined nanoparticles has a synergic effect on the fracture toughness of nanocomposites. Simultaneous use of 10 and 20 nm particles increased the fracture energy to about 770 J/m2. Finally, crack-opening displacement was calculated and found to be in the range of several micrometers which was much larger than the sizes of particles studied. Thus, the toughening mechanisms of crack pinning and crack deflection have a negligible effect on improvement of toughness, nevertheless, the plastic deformation and plastic void growth are dominant mechanisms in epoxy toughening by nanoparticles.

کلیدواژه‌ها [English]

  • epoxy
  • silica nanoparticles
  • fracture toughness
  • toughening mechanisms
  • specific surface area

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