Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Thermoplastic composites (TPCs) have shown significant advantages over thermosetting
composites. They have only been put into use recently and global knowledge in TPCs is
often proprietary, therefore a study into the application, processing and properties is of
importance. The aim of the study is to contribute knowledge in TPCs for South African
industry and academic institutions.
This thesis studies continuous fibre reinforced thermoplastics (CFRTPs), focussing on the
autoclave processing of commingled CFRTPs. A literature study provided background
knowledge to CFRTPs regarding processing techniques and mechanics.
Flexural testing and impact testing were performed on a variety of CFRTPs and
thermosetting composites (TSCs). These tests were performed to further understand
CFRTPs as well as to compare CFRTPs and TSCs. The flexural testing revealed that
CFRTPs have comparable strength and stiffness to the TSCs that were tested. They also
revealed that pre-consolidated sheets showed better and more consistent properties than
sheets made from commingled fabric. The impact testing revealed that the tested CFRTPs
and TSCs had similar impact resistance even though thermoplastic composites are
supposed to be more impact resistant. The tests also showed that thick unreinforced
thermoplastics had much higher impact resistance than the reinforced materials.
Manufacturing experiments were performed to establish sound processing methods of
CFRTPs. It was realised here that the high temperatures required to process the materials
require specific processing consumables and tooling. The experiments began by
processing flat panels in a convection oven with vacuum bagging techniques. They then
progressed to autoclave processing of parts with complex geometry.
An airline seat backrest was chosen as the case study in the application of CFRTPs. This
application requires structural strength and stiffness and also has strict fire, smoke, toxicity
and heat release (FSTH) requirements. Its geometry was sufficiently complex to
demonstrate the use of commingled CFRTP material. Backrests were made from both
CFRTPs and TSCs so that a comparison could be made between the two types.
The backrest was modelled using finite element methods (FEM) to determine an adequate
lay-up. This lay-up was then used for both the CFRTP and TSC backrests to ensure
similarity between the backrests of both materials. LPET (modified polyethylene
terephthalate) was the chosen thermoplastic matrix as it was more attainable than PPS
(polyphenylene sulphide) CFRTPs. The backrests of both materials were manufactured in
an autoclave with a vacuum bag method and then assembled using adhesives and bonding
jigs. Testing revealed that the stiffness and mass of the CFRTP backrests were very similar
to the epoxy backrests. This implies that commingled CFRTPs can replace the use of
TSCs in similar applications.
A basic cost comparison was also performed to compare the manufacture of CFRTP
backrests to TSC backrests.
Further work is needed to optimise processing time of these materials to make them more
competitive with TSCs. The processing time of commingled materials will probably never
be as quick as that of press formed pre-consolidated sheets. Their ability to be formed into
more complex parts does however make their use advantageous. / AFRIKAANSE OPSOMMING: Termoplastiese saamgestelde materiale (Engels: thermoplastic composites (TPCs)) toon
beduidende voordele bo termoverhardbare saamgestelde materiale. Hulle word eers sedert
onlangs benut en algemene kennis in TPCs is dikwels patentregtelik, dus is ’n studie van
die aanwending, prosessering en eienskappe daarvan van belang. Die doel van hierdie
studie is om ’n bydrae te lewer tot die kennis van TPCs vir die Suid-Afrikaanse industrie
en akademiese instellings.
Hierdie tesis ondersoek kontinue veselversterkte termoplastieke (Engels: continuous fibre
reinforced thermoplastics (CFRTPs)) en fokus op die outoklaafprosessering van vermengde
(Engels: commingled) CFRTPs. ’n Literatuurstudie het die agtergrondkennis rakende die
prosesseringstegnieke en meganika van CFRTPs verskaf.
Buigtoetsing en impaktoetsing is op ’n verskeidenheid CFRTPs en termoverhardbare
saamgestelde materiale (Engels: thermosetting composites (TSCs)) uitgevoer. Hierdie
toetse is uitgevoer om CFRTPs beter te verstaan asook om CFRTPs en TSCs te vergelyk.
Die buigtoetsing het onthul dat CFRTPs ooreenstemmende sterkte en styfheid het as die
TSCs wat getoets is. Dit het ook getoon dat vooraf-gekonsolideerde plate beter en meer
konsekwente eienskappe getoon het as plate wat van vermengde materiaal gemaak is. Die
impaktoetsing het onthul dat die CFRTPs en TSCs wat getoets is soortgelyke
impakweerstand gehad het, selfs al is termoplastiese saamgestelde materiale veronderstel
om meer impakweerstand te toon. Die toetse het ook getoon dat dik onversterkte
termoplastieke veel hoër impakweerstand gehad het as die versterkte materiale.
Vervaardigingseksperimente is uitgevoer om betroubare prosesseringsmetodes vir CFRTPs
vas te stel. Daar is besef dat die hoër temperature wat vereis word om die materiale te
prosesseer ook spesifieke prosesseringsverbruiksware en -gereedskap benodig. Die
eksperimente het begin met die prosessering van reguit panele in ’n konveksie-oond met
vakuumsaktegnieke. Daar is toe aanbeweeg na die outoklaafprosessering van onderdele
met komplekse geometrie.
Die rugleuning van ’n vliegtuigsitplek is gekies as die gevallestudie in die gebruik van
CFRTPs. Hierdie toepassing vereis strukturele sterkte en styfheid en is ook onderhewig
aan streng vereistes t.o.v. brand, rook, toksisiteit en hittevrystellimg (Engels FSTH). Die
geometrie daarvan was kompleks genoeg om die gebruik van vermengde CFRTP-materiaal
te demonstreer. Rugleunings is gemaak van beide CFRTPs en TSCs sodat ’n vergelyking
tussen die twee tipes gemaak kon word.
Die rugleuning is gemodelleer deur eindige element metodes (EEM) te gebruik om ’n
aanvaarbare oplegging te bepaal. Hierdie oplegging is toe gebruik vir beide die CFRTP en
TSC rugleunings om die gelykvormigheid tussen die rugleunings van beide materiale te
verseker. LPET (Engels: modified polyethylene terephthalate) was die gekose
termoplastiese matriks aangesien dit meer verkrygbaar was as PPS (Engels: polyphenylene
sulphide) CFRTPs. Die rugleunings van beide materiale is vervaardig in ’n outoklaaf met
’n vakuumsakmetode en toe geintegreer deur die gebruik van kleefstowwe en setmate.
Toetsing het getoon dat die styfheid en massa van die CFRTP rugleunings baie soortgelyk
was aan die epoksie rugleunings. Dit impliseer dat vermengde CFRTP die plek van TSCs
in soortgelyke gebruike kan inneem.
’n Basiese kostevergelyking is ook gedoen om die vervaardiging van CFRTP-rugleunings
teenoor TSC-rugleunings te vergelyk.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2132 |
| Date | 12 1900 |
| Creators | Mattheyse, Richard |
| Contributors | Van der Westhuizen, K., Van Rijswijk, Kjelt, 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 | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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