MultiMechanics Blog

Repost: Composites Design and the World Wide Failure Exercises

Posted by MultiMechanics on Jun 30, 2015 3:31:00 PM

It's beeen a while since we have waxed theoretical.  In this blog-post from January we explore some of the benefits and weaknesses of the empirically-minded approaches to composites analysis.  Enjoy. 

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In a previous blog, we talked about the importance of learning from failure in materials testing.  For better or worse, theoreticians have, in some ways, tried taken the burden of “learning from failure” off the plate of the common engineer.  Instead, they try to capture the insights gained from failure into flexible analytical theories; theories that (theoretically) allow us to predict a parts behavior, without knowing anything more than some material properties and part dimensions.  In computer science, this is known as abstraction.

The question is, Can composite failure theories sufficiently abstract all the nuance out of composites design? Do you need to understand the origins of a failure theory in order to use it properly?

Collectively evaluating individual failure theories:

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Topics: Composite Failure, Composite Design

Filament Wound Pressure Vessels and Space Shuttle Disasters

Posted by MultiMechanics on Apr 7, 2015 1:46:59 PM

One of the most visible symbols of American ingenuity and exploration over the past 50 years has been the progress and perseverance of the National Aeronautics and Space Administration (NASA). It is the epitome of human curiosity. It is a constant example of how we live with unknowns for only as long as technology limits our ability to explore; and sometimes we try and explore those unknowns before technology is ready.

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Topics: Composite Design

How Rule of Mixtures is Killing Your Composite Design

Posted by MultiMechanics on Feb 10, 2015 2:03:16 PM

What is considered a "composite" is always changing. Just as there is no single definition, there is also no single analytical method that can safely predict their dynamic behavior. The same way you can’t obtain ideal performance by using a single material throughout an entire car, you can’t expect to use a single analytical method to predict the behavior of all composites.

Rule of Mixtures is probably the most known, and widespread method of estimating composite properties. Its notoriety in composite design circles is also its main problem: Rule of Mixtures has been over used, and applied to cases that do not even come close to respecting its original, simplifying assumptions. If you wish to trust your analysis, it is essential to find out when it is OK, and (more importantly) NOT OK to use Rule of Mixtures. This article will describe what this rule really says, and will show some consequences of abusing this “rule of thumb” for composite behavior. 

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Topics: Composites Analysis, Composite Design

Top 5 Advanced Composite Cars at the Detroit Auto Show

Posted by MultiMechanics on Jan 27, 2015 1:00:00 PM

In 1899,  William Ernest Metzger helped organize the first Detroit Auto Show, and since 1907 the show has been running annually. 

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Topics: Composites Engineering, Composite Design

Composite Design and the World Wide Failure Excercises

Posted by MultiMechanics on Jan 20, 2015 11:30:00 AM

In our last blog, we talked about the importance of learning from failure in materials testing.  For better or worse, theoreticians have, in some ways, tried taken the burden of “learning from failure” off the plate of the common engineer.  Instead, they try to capture the insights gained from failure into flexible analytical theories; theories that (theoretically) allow us to predict a parts behavior, without knowing anything more than some material properties and part dimensions.  In computer science, this is known as abstraction.

The question is, Can composite failure theories sufficiently abstract all the nuance out of composite design? Do you need to understand the origins of a failure theory in order to use it properly?

Collectively evaluating individual failure theories:

Read More

Topics: Composite Failure, Composite Design