»
i forgot. vegetables contain a lot of water content. it is not wise to microwave them for more than 2 minutes.
♔ 10:47 AM
»
it seems like a lifetime
♔ Tuesday, April 27, 2010
10:18 PM
»
i'm so tired.
tired of it all.
needs to keep going. cant stop tonight.
♔ Monday, April 26, 2010
12:57 PM
»
decrivez votre annee a NTU.
en janvier, apres les vacances de Noel, je vais l'universite pour un nouveau semestre. Je commence le semestre le 15 janvier. En fevrier, nous avons une semaine de vacances.
En avril, j'ai des examens...
quand les examens sont finis, j'ai quatre mois des vacances!
♔ 11:28 AM
»
what scary weather >.<
why liddat.
♔ Sunday, April 25, 2010
7:44 PM
»
its going to be another sleep-less night.
sleep-less. as in, sleeping less. not no sleep.
bifang is incapable of not sleeping :(
♔ 3:38 PM
»
:( i need to focussss!! Studying too slowly, too unproductive!!
Sent from my HTC
♔ Saturday, April 24, 2010
9:45 PM
»
5 days more!
♔ Friday, April 23, 2010
9:26 PM
»
2 more to go.
♔ Thursday, April 22, 2010
12:45 AM
»
this is the first and hopefully the last time that bifang has a maths exam and she still hasn't slept at 12.
i hope the anxiousness for the first exam keeps me on my toes. i'm counting on it.. (>.<)
♔ Wednesday, April 21, 2010
11:17 PM
»
i really hope that i can be happy after the 29 april...
♔ 8:19 PM
»
:(
♔ 2:12 PM
»
tomorrow we'll be far away, tomorrow is the judgement day.. tomorrow we'll discover what our god in heaven has in store..
one day more.
now its just 24 more hours :(
♔ Tuesday, April 20, 2010
7:36 PM
»
22 APR 1300-1530 FE1007 VENUE: HALL E - SPORTS HALL 1 (SRC) SEAT NO.: 615
23 APR 1430-1700 AE2009 VENUE: HALL C, BLK N2, B2C-12, NORTH SPINE SEAT NO.: 116
26 APR 1700-1900 HMF1 VENUE: HALL F - SPORTS HALL 3 (SRC) SEAT NO.: 1051
29 APR 0900-1130 AE2006 AE2006 VENUE: HALL C, BLK N2, B2C-12, NORTH SPINE SEAT NO.: 221
must find the correct place. find the correct seat. go at the correct time. for the correct paper. dun forget the seat number.
♔ 6:24 PM
» :(
i'm freaking out..
♔ 10:18 AM
» :(
Im worried. Im afraid.
i feel unprepared. n yet thrs a limit to how much i can absorb everyday.
Just two days left :( Je suis triste.
Sent from my HTC
♔ Monday, April 19, 2010
10:55 PM
»
Fibreous reinforcement in PMC
Glass fibres provide good balance of mechanical properties and offer food corrosion resistance. E glass are commonly used for high density and low cost applications. S glass are relatively lighter and stronger and used for high load applications. Carbon fibres offer low density, lower coefficient of expansion, excellent strength and stiffness, and good fatigue resistance. However, they are brittle and conductive. Graphite fibres have higher young modulus. Aramid, also called Kevlar, fibres are heat resistant, strong, light, damage tolerant and extremely tough. However, they are poor in compression and very hard to cut and process.
Thermosetting resin matrices in PMCs
The most prevalent thermoset resins used for composite matrices are polyesters, vinyl esters, epoxies, bismaleimides, polyimides and phenolics. Polyesters are used extensively for continuous and discontinuous PMCs as they are relatively inexpensive and offer processing flexibility. Vinyl Esters are similar to polyesters bt are tougher and have better moisture resistance. Epoxies are the high performance matrix systems used primarily for continuous fibre composites. They can be used at temperatures up to 120-135 DC as they have a better elevated temperature performance. Bismaleimides are used in the range of 135-150 DC. Their processing is similar to epoxies, however they require elevated temperatures post-cure. Polyimides are very high temperature resin systems for use at 285-350DC but are diffcult to process. Phenolics are also high temperature resin system, but offer good smoke and fire resistance. They are used extensively for aircraft interiors.
Prepregs
These are ready to use forms of pre-impregnated reinforcement with matrix in it. They are available in three main forms: roving (collections of a few bundles or tows of fibres, either twisted or untwisted), unidirectional tape (bundles or tows of fibres woven to form a cloth for better stability and easy handling). They are fabricated by allowing a resin and hardener to impregnate the reinforcing fibres and cure the matrix partially to increase its viscosity such that it does not flow. Subsequently, the prepregs are stores in a freezer (generally -30DC) until its use in manufacturing. Cold storage prevents premature onset of cross linking reaction that will eventually cure the resin within prepreg. Such prepregs cannot be used and considered waste. Also, prepregs cannot be stored unlimitedly as teh resin matrix does have its own shelf life, beyond which quality degrades.
Prepregs, widely used in advanced composite industry, particularly aerospace industry, as they offer better control over resin wetting(flow, surround and adhere to fibre surface) and distribution. As seen in th eadjacent schematic of variety of prepregs, their quality depends on teh content and surface finish. A "good" (ie smooth and well impregnated) prepreg can result in laminates with voids and porousity. A partially impregnated prepreg wields high quality parts as it provides an evacuation path for air, and low temperature volatiles, entrapped in the lay-up. As the resin melts and flows. full impregnation occurs during the cure. A fully impregnated prepreg is acceptable, provided it has a rough surface( or corduroy texture), providing an evacuation path for volatiles.
As such prepregs are easy to handle, and also the fabrication can be automated, if necessary. Notwithstanding, the major drawback is the wastage in cutting.
Sandwich Composites
A typical sandwich construction has thin facesheet spaced on both sides of a thick core. In most cases, thin, strong stiff and relatively densefacings are combined with thick, relatively light cores. This combination provides a lightweight composite that is stronger and stiffer in most aspects than the sum of the individual stiffness and strengths. Sandwich construction is structurally efficient, often provides weight saving and therefore used extensively in aerospace industry. For example, with light cores, for the same facesheets and weight, their flexural rigidity increases by 6 and 48 times when the overall thickness is increased by twice and four times respectively.
The facesheet materials used generally include aluminium or composites, Core materials include metallic and non-metallic honeycomb core, balsa wood and foams. Honeycomb core, although strong in compression, core crushing can be detrimental to the strength of the sandwich. These are denser than honeycomb and primarily used for secondary, but complex structures. Foam cores, in which a continuous phase polymer is dispersed with gaseous cells, are used for light aircraft construction. Polystyrene, polyurethance and polyvinyl chloride fowams are commonly used. Syntactic cores, consisting of a resin matrix (eg epoxy) filled with hollow spheres or micro-balloons of glass or ceramic are also used. A suitable adhesive is selected for bonding the facesheets to the core. The drawback is possible moisture ingression and absorption by the adhesive leading to its degradation and causing subsequent debonding of the facesheets.
Metal Matrix Composites
MMCs use metals such as aluminium, nickel, cobalt as their matrices reinforced with either a)continuous fibres such as boron, silicon carbide, graphite or alumina or, b) wires of tungsten, beryllium, titanium and molybdenum or c) discontinuous materials such as fibres, whiskers and particulates. The reinforcements are chosen to increase stiffness, strength as well as heat and wear resistances. The MMCs can be classigied according to the type of reinforcement they use: The reinforcements can be particulates, single crystal whiskers, long aligned multifilament, monofilament.
ARGH I GIVE UP. theres too much stuff to type. its SLOW.
i read. focus and read. read and absorb. not memorise. absorb!!!!!!
♔ 10:05 PM
»
To let go of something i thought i needed, only to find out it was that very thing getting in the way of my getting ahead....
♔ 5:16 PM
» Ah haa
Tired.
I cant study with coffee.
Sent from my HTC
♔ 12:07 AM
»
i need to CONCENTRATEEE!!!!!!
NO TIME LEFT.
♔ Sunday, April 18, 2010
7:35 PM
»
tml, i must make it to the library.
MUST.
♔ 12:39 PM
»
:(
♔ Saturday, April 17, 2010
12:28 PM
»
Caught a cold. Terrible. Library too cold?
Sent from my HTC
♔ 11:11 AM
» test
testing
Sent from my HTC
♔ Friday, April 16, 2010
11:06 PM
»
focus today was topsss.
best i ever did for a long time.
but in terms of work done.. it does seem little... hai. and i've not finished that tutorial. that last question is difficult. and i have this nagging feeling that it will somehow or another be tested. just like how morgen came out for the evaluation.
perhaps my second home shd b the library. still think amk library better. the table bigger.
ah, or i'm just attached to that place.
♔ Thursday, April 15, 2010
5:07 PM
»
tutorial 11 is so demoralizing :(
i have decided.
no more tv. no more manga. no more facebook. no more msn. no more distractions. :(
ah. maybe onli left blogging. since there is only a limit to how much i can blog a day... i suppose.
♔ 3:56 PM
»
starting to wake up my idea.
cannot be so lazy anymore. must really start to focus.
really.
cant believe i actually couldn't find a seat in LWN. its the first time i see it so crowded. all the mugging.
♔ Wednesday, April 14, 2010
4:32 PM
»
i am buying a new pair of court shoes.
definitely.
♔ Saturday, April 10, 2010
11:32 PM
»
:(
maybe i will really adopt a policy of isolationalism. and stick to it.
til the war takes place.
♔ Friday, April 09, 2010
1:17 PM
»
♔ Thursday, April 08, 2010
4:44 PM
»
got a headache.
i cant believe i couldn't fall asleep.
okay. i did. but i just woke up with a headache. and not feeling refreshed at all.
terrible feeling.
♔ Wednesday, April 07, 2010
10:02 PM
»
i did not live until today... how can i live when we are parted... tml u'll b worlds awayyyyy n yet with u my world has started....
arghhhhhhhhhhhhhhhhhhhhhhhhh stupid song stuck in my head. la miserable. elle est miserable. je suis miserable?
tomorrow we'll discover what our god in heaven has in store.. one more dawn.. one more day.. one. day. more! :(
♔ Tuesday, April 06, 2010
10:52 PM
»
screwwed. aero mat test on thurs. n i left my notes at home.
how liddat.
♔ Monday, April 05, 2010
10:07 AM
»
and.. hell week begins.
hell week comprises of:
2 x CA (1 aero mat 1 maths2) 1 x tech comm presentation 1 x thermoassignment deadline 1 x (5hours?!) choir elective training (infinity) x of tutorials to finish...
:( please let me survive this week. then mayb... i stand a chance for the actual one that follows suit.
