7
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 believe Steps #2 and #3 are providing you a tolerance for the applied pressure.
So, for Step #2, it's telling you to apply 85 psig. You can go +15 psig higher (...
5
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 byproduct of machining.
Using a method like EDM will alter the properties of a polymer nearby, as it will heat the polymer. If you are interested in ...
5
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 composite materials
Several materials, prevalent mainly in the aerospace industry, are pre-engineered and pre-designed. GY70/339 is a common carbon fiber epoxy used ...
4
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:
$0.75(4)(7)$
$\frac{\pi(2^2)}{2}(0.75)$
$-\pi(1.25^2)(0.75)$
$1(4)(2)$
$-\frac{\pi(1.25^2)}{2}(1)$
Note: Negative areas as holes that need to be subtracted from the system.
X-Centroids are:
$2$
$2$
$2$
$0.5$
$0.5$
Y-Centroids are:
$-0....
4
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 hardening process, which in the case of typical epoxies may normally take place over several days, even weeks. The second benefit of heating the material is the ...
3
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 performance.
Epoxies are common because if you're using carbon fibres (rather than a variety of glass) you are evidently looking for a high performance component. ...
3
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, and the angle and energy of impact.
For example a low-velocity, unjacketed lead bullet might squash against the impact surface with little or no penetration, ...
3
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 observed brittleness and decreases the strain-at-failure and strain-at-rupture of the impacted materials.
There is a non-obvious limitation on penetration ...
3
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 the rule of mixtures. Consider a cross-section of the fiberglass laminate as shown below.
White regions are the fiberglass, black regions are the epoxy matrix....
2
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 fiber sheet, the epoxy, even with zero surface adhesion, will mechanically hold each fiber it encapsulates. I can not speak to what mechanical properties will ...
2
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 matter too much.
Assuming pinned supports, the original slab was therefore basically a simply-supported beam, with no moment at the ends and positive longitudinal ...
2
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 the manufacturer of the system.
It also depends on the requirements you have for the final part. If the final properties of the part are somehow safety relevant, ...
2
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 composite could have very low conductivity, depending on how the fibres are orientated. Equally fine metal fibres will have a layer of oxidation on the surface ...
2
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 and the strain.
If you consider the case where deformations are small, and just consider the stiff direction (tension/compression vertically and not horizontal ...
2
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. Instead, it's about making the most cost-effective structure possible.
Give me a material that weighs a billion tons per cubic centimeter but is cheap enough to let ...
2
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 job is to manage the stress levels in the most cost-effective manner. If a certain amount of concrete is capable of handling the compressive stresses less ...
2
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 Reinforced Plastics). It's hard to do well without special tools, especially in curved and/or hollow profiles, since you need to support the material around ...
1
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 matrix is some sort of thermosetting resin, and as a result it is relatively brittle. The thing is that the drilling process, will separate fibres from the matrix (...
1
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, fasteners, welding . Careful inventory control of the previous steel items. Coating of these shapes to reduce rust during construction. Inspection to verify the ...
1
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 run prohibitively high compared to concrete.
The next advantage is weight. In certain types of structure weight counts, such as underwater powerhouse. However, ...
1
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 film) and Breather. Both of these allow air to be removed from Mylar covered wing. Finally Vacuum Bag.
In assembly procedure:
Lay the fiberglass on the Mylar. ...
1
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.
Apart from little issue you are on the right track. Assuming that:
x is the horizontal axis
y is the vertical axis
then you are after $I_{xx}$.
Additionall, I'm ...
1
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 choices. Nowadays this is done with ABS or PBT. I don't know about your application though.
1
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 first modulus of elasticity because here this parameter will have a maximum. T700 is a standard modulus carbon fiber with a tensile modulus of 230 GPa, now the ...
1
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 aluminum section is 35.5in^3 and the S of steel 72.25/4.5= 16.05in^3
At yield point the steel plates can take a moment of
$ M_s= \sigma*S=18*16.05=288.9 k.in $
...
1
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 consider what happens if we bolt some very thin steel plates unto the flanges of the aluminum section. Then we can increase the load until the steel plates reach a ...
1
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 to lead to useful information. Chapter 2 "Bulk Solid Characterization", section 4 "Compressibility", references several sets of equations, each set from a ...
1
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 the fibers very very straight probably contributes somewhat as well.
Note also the 3+GPa claimed strength is for some "micro" composite. If you look elsewhere ...
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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 layer was prepared?
For example, does the answer change if the composite layer is a pultruded carbon-fiber strip? Looks like the fiber ratio is the same as ...
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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 increase the 'strength' of the fibers you'll eventually reach a point that the paste is the weak point, beyond which increasing the strength of the paper won't ...
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