7 votes
Accepted

How do I interpret the curing pressure of a composite from this data sheet?

Cure Procedure Apply vacuum of 22 inches (74 kPa) Hg minimum. Apply 85 + 15 – 0 psig (586 + 103 – 0 kPa) pressure for laminates. Apply 45 + 15 – 0 psig (310 + 103 – 0 kPa) pressure for sandwich. I ...
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  • 3,587
5 votes

How do I cut a crack into a polymer/plastic?

Since you used some specific words in your question, I will respond a certain way. Cracks are generated by mechanical action, and cannot be machined in. They may, in certain brittle materials, be a ...
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  • 241
5 votes
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How do I calculate an estimate for the properties of a composite material?

There are quite a few ways to find out the stiffness and/or strength of a composite material, with a good understanding of the materials that make up the composite material. 1. Pre-engineered ...
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  • 5,303
4 votes

For the machine element shown, locate the X, Y and Z coordinate of the center of gravity

Try this one. (Note: I don't know how to do tables in this site but please tabulate the data on your own.) Areas are: $0.75(4)(7)$ $\frac{\pi(2^2)}{2}(0.75)$ $-\pi(1.25^2)(0.75)$ $1(4)(2)$ $-\frac{\...
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4 votes
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Can you postcure epoxy composites outside the mold?

Yes it can be post cured - however, without support there is a risk of sagging or warping, particularly if it is a large and heavy part. Thermal curing is simply a way of speeding up the chemical ...
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4 votes
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Exactly what makes steel-concrete composite beam better than pure steel?

Some other answer have touched upon this, but I think it needs to be made explicit: Your mistake is in thinking that civil engineering is about making the lightest structure possible. It's not. ...
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3 votes

Exactly what makes steel-concrete composite beam better than pure steel?

The most important advantage of reinforced concrete over pure steel structure is availability. Many countries/regions on earth rely on imports for general goods production needs, the cost of steel can ...
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  • 7,253
3 votes

Exactly what makes steel-concrete composite beam better than pure steel?

I will make a slight add to the answers given here already, as follows. Take the case of a bridge. When loaded, some parts of it will be in compression, other parts will be in tension. The designer's ...
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3 votes

Can the phrases “carbon fibre reinforced polymer composites” (CFRP) and “carbon fibre-epoxy composites” be used interchangeably?

No. You could use other polymers. Polyesters, vinylesters, and epoxies are all common in fibre-polymer composites and could be used. You can also use other special stuff if you need, eg, fire ...
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  • 602
3 votes

Impact load of a bullet on a laminate

An additional complication is the behaviour of the bullet itself on impact, which is not only difficult to model but can vary a lot according to the construction of the bullet, it's geometry and mass, ...
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3 votes
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Impact load of a bullet on a laminate

Expanding on the comment by @grfrazee, it isn't as simple as with a static load. Several non-linear parameters change the response of the composite component. Extremely high strain rate increases the ...
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  • 3,971
3 votes
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How do I calculate the structural properties of a fiberglass laminated wood panel?

To determine the properties of a composite laminate, the properties of each component and their relative volume fractions must be known. The properties of glass fiber laminate may be determined using ...
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  • 3,971
2 votes
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How strong is the adhesion between UHMWPE Fiber and Epoxy Resin?

I am not a chemist or material scientist, but it is my experience that reliable adhesion to a smooth Polyethylene surface is nearly impossible even with "plastic" rated epoxy. However where it is a ...
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  • 7,444
2 votes
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Assessment of a concrete beam being strengthened by an additional steel member

It isn't clear from your sketch whether the end supports are fixed or pinned, so I'm going to assume they were pinned. However, this is going to be a qualitative answer, so that doesn't actually ...
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2 votes

Can you postcure epoxy composites outside the mold?

Curing conditions depend on the resin sytem. Some systems require a minimum temperature for a certain duration to cure, others cure completely at room temperature. If in doubt, you will need to ask ...
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  • 679
2 votes

Design a composite material with good wear resistance and electrical conductivity

One problem is that you may not have good contact between adjacent metal fibres. In general resin/fibre composites aim to completely coat the fibres so it is entirely possible that a metal/plastic ...
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2 votes
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Young's modulus for composite auxetic material

Rather than thinking about a Young's modulus directly, the problem becomes easier to grasp if you think in terms of a relationship between the load and displacement, and subsequently between stress ...
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2 votes

Bending stiffness of composite shaft

The bending stiffness will be determined by the second moment of area ($I$). The formula you provide $\int\int r^2 da$ is for the Polar Moment of area ($J_p$), and is valid for torsional problems. ...
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  • 22.6k
2 votes

Exactly what makes steel-concrete composite beam better than pure steel?

A partial listing ( in addition to the previous answer) ; for reinforced concrete only simple generic shapes are needed ( bars) while steel only needs "I" , "H" beams, gussets, ...
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  • 5,720
2 votes

What Are The Recommended Binding Methods For A Carbon Fibre Chassis Frame?

Cool that you're considering CF, it's a fun material. So first, to answer your questions. If done right it can be fine, but even then it's the least preferable (in my opinion) way to bond FRPs (Fiber ...
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1 vote
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What Are The Recommended Binding Methods For A Carbon Fibre Chassis Frame?

This is Work-in-progress How does drilling holes into carbon fibre affect its structural integrity? Drilling holes into carbon fibre has very adverse affects. The main reason is that usually the ...
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1 vote

Why use Mylar for vacuum bagging

From Vacuum Bagging Wings Instruction Manual Purdue University Inner layer is foam with Kevlar at wing tip. Next fiberglass resin. Then Mylar with tape at tip. Then Perf Ply (perforated release ...
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1 vote

How to know the material of key-top?

Have you heard of double shot moulding? In this process, the white is a separate molding that is actually embedded behind the black key. This would not show wear and might narrow down your material ...
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  • 3,085
1 vote

Composite materials

A unidirectional composite material cannot have the same modulus in all directions. Unidirectional means that all fibers run in the same direction. Obviously, this direction defines the axis for the ...
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1 vote

Composite beam- increase in bending moment due to reinforced steel

Let's approximately calculate the S of composite beam, knowing that aluminum section I is 146in^4. $ I_{COMP}= I_{alum}+ 2*A_{steel} *4.25^2 = 146+(8*0.25*2)4.25^2=146+72.25=218.25in^4 $ The S of ...
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1 vote

Composite beam- increase in bending moment due to reinforced steel

The difference in stiffness is important. First let's consider the aluminum W8x40 section without any steel plates: It can be loaded until the aluminum reaches a stress of 12 ksi. Then let's ...
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  • 1,203
1 vote
Accepted

What are equations related to the compaction of composite metal powders?

assuming you cannot compress more than the true density, is there a formula to determine how much force corresponds to the density achieved? I scanned through some literature and found this book ...
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1 vote
Accepted

Why is graphlite so strong in tension?

Its not about the tension in the final product. [They are claiming] tension during fabrication buys them a much higher fiber loading. See 67 vol%.. a typical "wet layup" is maybe half that. Having ...
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  • 979
1 vote

How to calculate scarf ratio or lap overlap for composites?

Formulas from "The Behavior of Structures Composed of Composite Materials". Consider this source material for a much deeper understanding of composites. Does the answer depend on how the composite ...
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  • 5,303
1 vote

Can we make engineering grade paper mache by improving on the paper?

Absolutely. Paper mache at it's core is an early predecessor of carbon fiber. The paper is the fiber structure and the paste (not sure of the technical term) is the equivalent to the epoxy. If you ...
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