نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار، مهندسی مکانیک، دانشگاه تربیت دبیر شهید رجایی، تهران.

2 کارشناسی ارشد، مهندسی مکانیک، دانشگاه تربیت دبیر شهید رجایی، تهران.

10.22068/jstc.2020.116440.1599

چکیده

در سالهای اخیر به دلیل دستیابی به خواص مورد نظر و مطلوب از کامپوزیتها در صنایع مختلف استفاده می‌گردد. تعیین دقیق مکانیزمهای تخریب کمک شایانی به تصحیح طراحی و تحلیل بارگذاری در کامپوزیتها و بخصوص پانلهای ساندویچی می‌نماید. در این مقاله با تحلیل داده های آکوستیکی، به بررسی و تشخیص مکانیزمهای خرابی در پانلهای ساندویچی کامپوزیت پلی استر/ شیشه با هسته فوم پلی اورتان در آزمون خمش سه نقطه با اعمال تضعیف اولیه حاصل از ضربه‌های با انرژی مختلف پرداخته ‌شده ‌است. بدین منظور نمونه‌هایی با 4 لایه‌چینی متفاوت و با 4 حالت مختلف با و بدون پیش ضربه مورد استفاده قرار گرفت. شکست ماتریس، جدایش الیاف از ماتریس، شکست الیاف و شکست فوم بعنوان مکانیزمهای تخریب غالب، از روی تصاویر چشمی، بررسی وقایع آکوستیک رخ داده در بازه‌های فرکانسی مختلف، استخراج انرژی هر بازه و بررسی نمودار نیرو-زمان تعیین شده‌اند. نتایج حاصل‌شده نشان داد که مکانیزمهای شکست ترد شامل شکست ماتریس و شکست فوم در هر رویداد مختلف آکوستیک، مجموع انرژی های بالاتر با پراکندگی کمتر در بازه فرکانسی پایینتر نسبت به مکانیزمهای شکست نرم مانند شکست الیاف شیشه آزاد می‌کنند. اما رویداد‌های آکوستیک در مکانیزم شکست نرم الیاف شیشه با مجموع انرژی های کمتر و بصورت پراکنده در بازه فرکانسی بالاتر اتفاق افتاده است. تطبیق تصاویر چشمی با داده‌های آکوستیکی و همچنین نمودار نیرو جابجایی، علاوه بر صحه گذاری درتعیین مکانیزمهای تخریب در این پانلهای ساندویچی، منجر به تعیین بازه فرکانسی جدید شکست فوم متخلخل (190 الی220 کیلوهرتز) نیزگردید.

کلیدواژه‌ها

عنوان مقاله [English]

Applying acoustic emission to investigate failure mechanisms on bending of polymer-based composite sandwich panels

نویسندگان [English]

  • Seyed Reza Hamzeloo 1
  • Amir Refahi Oskouei 1
  • Amir Mohamad Zakizadeh 2

1 Department of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran.

2 Department of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran.

چکیده [English]

In recent years, due to achieving desired properties, increasing application of Composite in various industries is observable. Exact determination and evaluation of failure mechanisms lead to modified designs and helps assessment of loading in composite structures, specially sandwich panels. In this paper, failure mechanisms during bending of Foam / Glass - Polyester Sandwich panels, which degraded by pre-impact of various energy, have been investigated by acoustic data analysis. 4 different Lay-up techniques for laminates with 4 types of with and without pre-impacts and totally 16 samples were studied. Matrix crack, fiber de-bonding, fiber breakage and foam crack were the mechanisms were investigated through sample failure photos, acoustic frequency count analysis, extracted energy in each frequency range and force-time diagrams. Results showed that brittle failure mechanisms containing matrix crack and foam crack release more condensed and in lower frequency range with higher energy acoustic counts in comparison with ductile failure mechanisms like as fiber de-bonding and fiber breakage. Ductile failure mechanisms release more scattered in higher frequency range but with lower energy acoustic counts. Acoustic Results which applied to assess failure mechanisms validated by visual pictures and force diagrams also lead to a new frequency range determination for foam crack (190 to 220 kHz).

کلیدواژه‌ها [English]

  • Acoustic emission
  • Sandwich Panel Composite
  • failure mechanisms
  • Bending

 

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