Use of lightweight materials is an important part of reduction of fuel consumption by commercial aircraft. A considerable number of structural aircraft parts are therefore built of thin layers of epoxy pre-impregnated carbon fibres stacked to laminates. Manufacturing these by hand is costly and different methods of automation have therefore been developed. One cost-effective way of manufacturing is Automated Tape Lay-up of flat stacks followed by a Hot Drape Forming operation. A well-known problem in the industry within forming is fibre wrinkling, which can cause a serious strength knock down. The focus of this thesis has therefore been on understanding how and why wrinkles develop during forming of multi-layer stacks and, based on this, investigate different methods for process and material improvements. The work presented initially investigates the dependency between stacking sequence and wrinkle development. It is shown that wrinkle free forming can be obtained by changing the fibre stacking order. In the following investigation it is shown that the wrinkles cannot be entirely eliminated by local stiffening of the critical layers. In a, related study it is shown that different kinds of wrinkles develops during forming; wrinkles may be either due to global buckling of the entire lay-up or local compression of single layers. Global buckling is due to excessive material. Local compression occurs as the material shear during forming. The work presented leads to an understanding of the importance of making the beneficial neighbouring fibre layers interact during forming. One way to connect neighbouring layers is to tailor the interlayer properties. A study is presented that shows how local manipulation of interlayer properties may steer the multi-layered material into a different deformation mechanisms. The manipulation in this thesis is performed using Multi Wall Carbon Nano Tubes, thermoplastic veils or consolidation of thermoplastic toughener particle interlayers. / <p>QC 20160425</p>

<p> To reduce cost of structural composites the development of more efficient manufacturing methods is of great interest. Sheet forming of thermoset prepreg, also known as hot drape forming, has been a promising manufacturing method for decades. An automatic tape layer (ATL) can be used to perform the lay-up in an efficient way. The flatly stacked unidirectional prepreg forms a sheet to be formed over a given mould. Knowledge about the materials forming behaviour is important to reach the required shape without flaws, such as wrinkles.</p><p>An experimental approach is developed to investigate the intra- (within the layer) and interply deformation. The intraply deformation properties are registered by the use of a bias-extension test and a digital image correlation (DIC) equipment. To measure the interlaminar (between the layers) friction in the prepreg/prepreg interface a specialized rig is designed and built.</p><p>The two tested materials are Cycom^® HTA/977-2 from Cytec and HexPly® T700/M21 from Hexel, which are examples of the second and third generation of carbon fibre/epoxy prepreg. Where M21 includes craze stoppers in form of thermoplastic particles, the 977-2 has the same function but in melted stage. These particles seem to influence both the intraply deformation modes and increase the level of friction between layers.</p><p>The results from the bias-extension test was compared with the theory of pin-jointed net (PJN) and it was found that M21 behaves accordingly. The measured rotation for 977-2 is less than the theoretical, this due to slippage. The rate of deformation seems to have an influence not only on the load level, but also in the mode of deformation. Both for the interlaminar and intraply deformation the resistance to motion were much larger for M21 than 977-2.</p> / KEKS (kostnadseffektiva kompositer)

The positions of high stress concentration in a bicycle frame structure made in composite materials and a way to strengthen them were investigated via SolidWorks and ANSYS, 3D picture plotting software, and numerical simulation software, respectively. The capability of productivity will be improved indirectly due to the shortening of the time in the process of customers¡¦ order, research, development and mass production. In experiment, prepreg tape (TOHO UT500 carbon fiber/AD. Group matrix) which were produced by AD. Group were made into laminates by hot-pressing machine. The material constants of the laminate and the stress-strain diagram were obtained according to the stander of ASTM D3039. The received material constants are E11 =151.55 GPa and E22 = 7.654 GPa, respectively. In simulation, the experimental data E11 and E22 were used in the numerical analysis, and obtained the stress and deformation fields of the bicycle frame structure and the front fork were plotted based on the standards provided by AD. Group. Reinforcements were made according to the positions of stress concentration in the diagrams. The results of improvements of the front fork after reinforcement include¡G the deformation of normal rigidity was improved to 9.45mm from 12.89mm, and the lateral deformation was significantly improved to 0.97mm from 13mm. Other improvements of the frame structure after reinforcement contain the deformation: dual-side rigidity was improved to 6.6mm from 11.7mm, and the deformation of single-side rigidity was improved to 12.5mm. The rigidity of the head lug was 0.46mm and there is no need to reinforce it because it was meets requirements. Keywords: Numerical analysis, bicycle frame, prepreg, stress concentration.

Universiẗat, Diss., 2005--Stuttgart.

To reduce cost of structural composites the development of more efficient manufacturing methods is of great interest. Sheet forming of thermoset prepreg, also known as hot drape forming, has been a promising manufacturing method for decades. An automatic tape layer (ATL) can be used to perform the lay-up in an efficient way. The flatly stacked unidirectional prepreg forms a sheet to be formed over a given mould. Knowledge about the materials forming behaviour is important to reach the required shape without flaws, such as wrinkles. An experimental approach is developed to investigate the intra- (within the layer) and interply deformation. The intraply deformation properties are registered by the use of a bias-extension test and a digital image correlation (DIC) equipment. To measure the interlaminar (between the layers) friction in the prepreg/prepreg interface a specialized rig is designed and built. The two tested materials are Cycom® HTA/977-2 from Cytec and HexPly® T700/M21 from Hexel, which are examples of the second and third generation of carbon fibre/epoxy prepreg. Where M21 includes craze stoppers in form of thermoplastic particles, the 977-2 has the same function but in melted stage. These particles seem to influence both the intraply deformation modes and increase the level of friction between layers. The results from the bias-extension test was compared with the theory of pin-jointed net (PJN) and it was found that M21 behaves accordingly. The measured rotation for 977-2 is less than the theoretical, this due to slippage. The rate of deformation seems to have an influence not only on the load level, but also in the mode of deformation. Both for the interlaminar and intraply deformation the resistance to motion were much larger for M21 than 977-2. / KEKS (kostnadseffektiva kompositer)

No description available.

abstract: This study investigates the fabrication and mechanical properties of semicontinuous, hemp fiber reinforced thermoset composites. This research determines if off-the-shelf refined woven hemp fabric is suitable as composite reinforcement using resin pre-impregnated method. Industrial hemp was chosen for its low cost, low resource input as a crop, supply chain from raw product to refined textile and biodegradability potential. Detail is placed on specimen fabrication considerations. Lab testing of tension and compression is conducted and optimization considerations are examined. The resulting composite is limited in mechanical properties as tested. This research shows it is possible to use woven hemp reinforcement in pre-impregnated processed composites, but optimization in mechanical properties is required to make the process commercially practical outside niche markets. / Dissertation/Thesis / M.S.Tech Engineering 2012

The subject of this master’s thesis is manufacturing design and production of CFRP swingarm prototype for off-road motorcycle. Theoretical part describes conventional types of swingarm, provides basic introduction to composites and manufacturing technologies. Practical part describes production steps, assembly jigs and assembly process. The last part of thesis deals with measuring stiffness properties using photogrammetry system TRITOP.

In the diploma thesis there was made an attempt to compare the samples of carbon fiber composite materials (carbon). The teoretical part presents knowledge of the composition of composite material. Next, there is described the production and possible use of carbon composite materials in various technological branches. In the practical part the thesis focuses on the testing of composite materials made of carbon fiber with different orientation and weights of fibers. There is performed a tensile test and simultaneous monitoring of the course of the tensile test by acoustic emission. Finally, the statistical processing of the measured values occurs.

Undersökning har gjorts av möjligheten att återvinna uttjänta lakan från textilserviceföretaget Textilia till tillverkning av prepreg. Då dessa lakan, till skillnad mot mycket annat textilavfall, utgör en kontinuerlig resurs av relativt konsekvent kvalitet, finns stora möjligheter att tillverka en produkt av detta. Detta skulle även innebära att förbränning av lakan undviks samt att ett bättre utnyttjande av resurser åstadkoms. Stapelfiber av bi-komponent i polyester har tillförts väven genom nålning, samma typ av nålning som används vid non-woven-tillverkning. Genom att nålarna har fört bikomponentfibrer ner genom lakansväven har en mekanisk bindning skapats mellan väv och bi-komponent. Väven blir således en bärare av bi-komponenten och dessa har sedan värmepressats ihop till ett kompositmaterial. Dock orsakar nålningen brott i vävens trådsystem. Tester har genomförts för undersökning av mekaniska egenskaper hos ensam väv och färdig komposit. Ett tydligt resultat var att nålning signifikant försämrade vävens dragstyrka men hos färdig komposit gjorde nålning endast mindre påverkan på mekaniska egenskaper. Med förändringar i nålningsdjup och nålningsdensitet tros försvagning av väv bli lägre och färdig komposit påverkas än mindre. / Program: Textilingenjörsutbildningen