Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The development of light and sti aerospace structural panels is very important in the
aerospace industry, e.g. a lighter satellite requires less fuel to launch it into space which
in turn saves money for the owner of the satellite. This thesis describes the design,
optimisation, manufacturing and testing of a ribbed light alloy core - carbon bre face
sheets, sandwich-type, satellite panel operating at launch loading conditions (115 m/s2
accelerations and requiring a minimum structural natural frequency of 90 Hz) to determine
the optimum sti ness per mass ratio of the panel.
The panel layout was based on a satellite panel designed by SunSpace and Information
Systems for the Sumbandila satellite. Only the black box mounting positions of the original
panel were used in the optimisation of the new panel. The core of the evaluation panel
was manufactured from aluminium (6082-T6). The carbon bre skins were manufactured
from unidirectional high modulus carbon bre (K63712) in a [0/90/0] wet layup with
the 0± direction in the longitudinal direction of the panel. A three-dimensional model of
the panel consisting of 3D wedge elements and containing all the boundary conditions
was modelled with the use of the nite element software MSC Patran. The model was
optimised with the use of optimisation software Genesis to locate the rib positions. Genesis
removes all the elements containing the least amount of stress; only 30% of the core
elements were kept while restricting the elements to form an extruded con guration (for
milling machining) throughout the thickness of the panel. The rib elements remaining
were replaced in MSC Patran by shell elements and the shell element thicknesses were optimised
with the use of Genesis to ensure the lightest and sti est possible structure. The
optimised rib thicknesses were imported into MSC Patran and the numerically optimised
model could then be analysed with MSC Nastran.
The numerical model was converted into a manufacturable structure and the core was
machined from a solid aluminium sheet. The ribs were machined in the shape of an Ibeam
to allow for minimum weight and a su cient bonding area for the two carbon bre
face sheets. Elevated circular surfaces, protruding through the carbon bre sheets, were
machined in the position of the black box mountings to allow for better heat transfer
away from the black boxes. The carbon bre face sheets were bonded to the metal core
(3M Scotch-Weld 9323 B/A). The nished panel was put through various tests to determine whether it is suitable
for use in the aviation industry. The tests included modal testing, random vibration
testing and temperature testing to determine if the structure is durable enough for use in
satellites.
The test results are promising and show that a substantive amount of money can be
saved by reducing the mass on the structure. By using optimisation software and ribbed
light alloy - carbon bre face sheets sandwich structures the performance of the structures
can be improved without adding mass to the structure. / AFRIKAANSE OPSOMMING: Die ontwikkeling van ligter en stywer lugvaartstruktuur panele is baie belangrik in die
lugvaart-industrie, bv. 'n ligter satelliet benodig minder brandstof om tot in 'n wentelbaan
lanseer te word. Dit bespaar sodoende lanseerkostes vir die eienaar van die satelliet. In die
verslag word die ontwerp, optimering, vervaardiging en toets van 'n gewebde, ligte allooi
kern - koolstofveselvel, saamgestelde materiaal, satelliet struktuurpaneel wat onderwerp
word aan lanseer belastingstoestande van ongeveer 115 m/s2 versnellings ondersoek. Die
tegnieke word gebruik om die optimale styfheid per eenheidsmassa-verhouding te bepaal.
Die paneel benodig 'n minimum strukturele eerste natuurlike frekwensie van 90 Hz.
Die basiese paneel uitleg is verkry vanaf 'n satellietpaneel wat deur SunSpace and Information
Systems ontwerp is vir die basisplaat van die Sumbandila satelliet. Die enigste
geometrie wat van die oorspronklike struktuur behou is om die nuwe struktuur te optimeer
is die vashegtingspunt-posisies van die swart-kassies. Die kern van die ge-optimeerde
struktuur is vervaardig uit gemasjieneerde aluminium (6082-T6). Die koolstofvesel-velle
is vervaardig uit enkelrigting hoë-modulus koolstofvesel-doek (K63712). Die oplegging is
gedoen met 'n nat-opleggingsproses waar die drie lae van elke vel 'n [0/90/0] oriëntasie
het met, die 0± lae in die langsrigting van die paneel. 'n Drie-dimensionele eindige element
model van die paneel is geskep met behulp van die MSC Patran sagteware pakket met die
model hoofsaaklik opgebou uit 3D wig-elemente. Al die lanseertuig vashegtingsrandwaardes
is in die eindige element model ingebou. Om die web posisies te bepaal is die Genesis
optimeringsagteware pakket gebruik. Verskeie ontwerpsvoorwaardes is gespesi seer waaraan
die optimeringsproses moes voldoen. Slegs 30% van die wig-elemente mag behoue bly
in die optimeringsproses en al die elemente deur die dikte van die paneel moet of behou
of verwyder word. Dit verseker dat die resultaat masjieneerbaar is met 'n freesmasjien.
Die oorblywende wig-elemente is in MSC Patran vervang met dop-elemente. Die dopelemente
se diktes is ge-optimeer met Genesis om die ligste en styfste struktuur moontlik
te kry. Die ge-optimeerde dop-element diktes is in die MSC Patran model ingetrek. Die
numeries ge-optimeerde model is daarna met behulp van MSC Nastran ge-analiseer. Nadat die numeriese model omgeskakel is in 'n vervaardigbare struktuur is die kern
gemasjieneer uit 'n soliede blok aluminium. Die webbe is ontwerp en vervaardig in 'n
I-balk vorm. Dit laat toe dat die webbe 'n minimum gewig en genoegsame area het
waarop die koolstofvesel velle geheg kan word. Verhewe vlakke is gemasjieneer op die
aluminium kern in die posisies van die swart-kassie vashegtingpunte. Hierdie verhewe
vlakke steek deur die koolstofvesel-vel aan die kant waar die swart-kassies vasgeheg word.
Dit verseker 'n metaal-op-metaal verbinding tussen die kern en die swart-kassies vir beter
hittegeleiding. 3M Scotch-Weld 9323 B/A epoksie is gebruik om die koolstofvesel-velle
aan die aluminium kern te heg.
Die voltooide struktuur is aan 'n reeks toetse onderwerp om te bepaal of dit geskik
is om in die ruimtevaart-industrie gebruik te kan word. Dit sluit modale toetse, lukrake
vibrasie toetse en temperatuursverandering toetse in. Die toetsresultate sal bepaal of die
struktuur duursaam genoeg is om in satelliete gebruik te word.
Die toetsresultate is belowend en dui daarop dat deur massa te bespaar op die struktuur,
'n aansienlike bedrag op satelliet lanseer-kostes bespaar kan word. Deur optimeringsagteware
tesame met gewebde ligte allooi kern - koolstofvesel vel, saamgestelde materiaal
strukture te gebruik kan die werksverrigting van die strukture verbeter sonder dat
massa bygevoeg word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4151 |
| Date | 03 1900 |
| Creators | Roets, Philip J. |
| Contributors | Van der Westhuizen, K., University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 107 p. : ill. |
| Rights | University of Stellenbosch |
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