Searching for compressive stress of silica aerogels

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Discussion Overview

The discussion centers around the compressive stress and strength of silica aerogels, particularly in relation to data from a specific paper on cyanoacrylate reinforcement. Participants explore the relationship between three-point bending tests and compressive strength, as well as the challenges in finding comprehensive data on various silica aerogels.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant seeks to understand if internal stress can be calculated from rupture strengths provided in a paper on silica aerogels.
  • Another participant argues that three-point bending tests measure tensile strength, not compressive strength, and highlights the differences in how these properties are assessed.
  • A later reply emphasizes the variability in compressive strength across different materials, using steel and concrete as examples.
  • One participant expresses difficulty in finding specific data on compressive strength, density, and types of silica aerogels, requesting charts or resources that compile this information.
  • Another participant suggests a search term to find relevant literature, noting that some results may be behind paywalls.
  • A participant provides an approximation of compressive strength for cyanoacrylate reinforced silica aerogel under specific conditions, expressing disappointment in the strength compared to expectations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the ability to derive compressive strength from bending test data, and there are multiple competing views regarding the properties of silica aerogels and the challenges in obtaining relevant data.

Contextual Notes

Limitations include the dependence on specific testing conditions and material properties, as well as the lack of comprehensive charts or databases for silica aerogels.

lavalite
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I have no formal training in any type of engineering, so if my request is confusing, I apologize.

I believe I am seeking data on the ultimate internal stress of various silica aerogels in compression mode.

I found a paper published by Dylan J. Boday where CVD of cyanoacrylates was used to reinforce the aerogels (1). A three-point compression analysis and rupture strength is discussed, but not internal stress. Is it possible to calculate the internal stress from the listed rupture strengths?

(1) Boday, D. et al.; chemistry of materials, 2008, 2009, 2847
 

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You apparently want to find the compressive strength of various silica aerogels from the three point bending strength in that paper. Not possible, because they are measured differently and measure different properties.

The specimen in a three point bending test typically fails in tension, in which case the test measures the tensile strength in the presence of surface defects. Compressive tests are normally not sensitive to surface defects, so compressive strength can be greater than the result of a three point bending test. This is material dependent. Steel, for example, has compressive strength close to tensile strength, while concrete has tensile strength about 8% of compressive strength.

Good search terms to learn more are mechanical properties aerogel.
 
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Ok thanks a lot, I appreciate your reply and help.
 
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jrmichler said:
You apparently want to find the compressive strength of various silica aerogels from the three point bending strength in that paper. Not possible, because they are measured differently and measure different properties.

The specimen in a three point bending test typically fails in tension, in which case the test measures the tensile strength in the presence of surface defects. Compressive tests are normally not sensitive to surface defects, so compressive strength can be greater than the result of a three point bending test. This is material dependent. Steel, for example, has compressive strength close to tensile strength, while concrete has tensile strength about 8% of compressive strength.

Good search terms to learn more are mechanical properties aerogel.

I have attempted to use the search term that you suggested but I'm still having difficulty finding the information that I'm trying to find. I really wish I could find a chart that had information like type, density, and compressive strength. Does anybody know where I can find charts that have that information?
 
I'll check that out, thanks for the link Tom!
 
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WARNING: Assumptions and approximations ahead!

The compressive strength at failure of cyanoacrylate reinforced composite silica aerogel (1) may be as high as 166,084pa at a density of 0.22g/cm^3 if;

  • The sample can support 3200 times its own weight in true compression.
  • The sample is cylindrical.
  • The sample is twice as tall as its diameter.
  • The sample is 2.3 times its unreinforced mass of 0.262g.
Sadly, if this approximation is even close to correct, then this material is 60 times weaker than I'd hoped for it to be. I guess it's back to the drawing board.

(1) Boday D.J.; et al Applied Materials & Interfaces, 2009, 1365-1366
 
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