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So...what's in a hole tolerance anyway?

Composite Hole Tolerances The hole diameter relative to the bolt diameter is critical when assessing maximum bearing strength. Gaps of 0.004 in. have analytically been shown to  increase the peak stresses by as much as 36% . The typical recommendation is to design near or net fit clearances in bolted joints when able; ...
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Plate Warping when Unbalanced!? Not exactly...here's a Tip!

"There is a misconception that unbalanced laminates are not recommended because the laminates will warp when temperature and/or moisture content changes. Symmetric laminates, whether balance or not, will not warp , while unsymmetric laminates will. Material symmetry, such as orthotropy or anisotropy, has no effect on warpage." Note: "Laminates have...
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Got Flatwise Tension?

Composites…It's not just a 2D world…Got Flatwise Tension?  Too often I hear both analysts and designers toss around the term quasi-isotropy…a mythical monster to some...an in-plane idealization that simplifies a 3-D problem for others. I for one am guilty…because I appreciate the fact that you can take a 3-D analysis and knock i...
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Is your laminate special?

I would like to think that all my laminates are special…and I'm sure that, well, all of your laminates are special too! Hmmm…this is starting to sound like an intervention! Well, not quite…what I'm actually referring to is a type of layup that excludes the use of angle plies; in turn, greatly simplifying a preliminary analysis via&nb...
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Keep it Simple...the design that is!

Ah yes, the most complex problems are often solved with the simplest of solutions. Have you ever heard that somewhere before…bet you have! But do you practice it!? Perhaps not…no worries, because it now seems that solving engineering problems by leveraging the ubiquitous numerical titan known as FEA is the preferred problem-solving apparatus over a...
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Quasi-Isotropy…wait…what is that?

What is it you ask…well, this is one of my favorite meals. A large quasi-isotropy with a side of fries and coke. LOL…but of course is isn't…actually, this is a laminate, that when constructed correctly, emulates a metallic material having an isotropic relationship defined as: E x = E y = E θ A general rule for describing a quasi-isotropic layu...
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The Free Edge Effect

The free edge effect is an inter-galactic phenomenon found on the outer reaches of the cosmos that leads to a parallel…well…no, not exactly. What I'm referring to is a region within a laminate that produces three-dimensional stresses at or near a free edge; then decays rapidly as the stress moves away from the free edge. This stress is commonl...
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The Volkersen’s Method

​ Make that overlap length as long as possible…the longer the better I always say…we don't want that bonded joint to fail…says the confident designer with an unparalleled surety…or, is it absurdity…hmmm. Well, for those of you interested in approximating the performance of an adhesively bonded joint "quickly" while adhering to some basic ...
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Balanced verse Unbalanced Laminate - What's Yours?

So how do we know that we have an unbalanced laminate in the first place? Moreover, if you end up with an unbalanced layup, what are the implications? Good questions to have answers to before signing-off on that laminate design.  Firstly, a perfunctory definition is in order regarding a balanced laminate. A designer will need to ensure that fo...
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What are your Strengths…”Specific” that is?

When your being interviewed for a job be prepared to answer a classic interview question regarding your strengths. This is an invitation to talk about your skills…perhaps its analytical thinking; or, maybe organization…wait-just-a-minute, wrong topic! The strength I am referring to matters when one is considering the strength of a material. So, do ...
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Got Shear Lock?

Funny…I was at the barber the other day and he kept complaining about his shears locking up…pesky scissors keep jamming on me he said! Well…obviously this is nothing but banal witticism, because that's surely not what this article is about. I draw your attention to an experience I had regarding a fabric drapeability study that I performed to evalua...
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