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

The cost of manufacturing high quality composite components can be significantly reduced by using Out of Autoclave (OOA) processes if they can achieve final parts with a finish quality as high as that obtained using an autoclave process. Much research has been carried out recognising that regardless of the reinforcement fibre orientation, manufacturing of preimpregnated (prepregs) carbon components is much affected during its forming stage by fibre deformation and failure modes. This work sought to reduce wrinkling in the moulding of prepregs by introducing slip layers within the lay-up. Three types of slip layers were used: a dry fabric, a resin rich layer and a resin film. In order for the slip layers to be fully incorporated into the final laminate the resin content within the slip layer must be adjusted prior to crosslinking. In the case of dry fabric layer, additional resin must be introduced and in the case of a resin rich layer and resin film layer, excess resin has to be removed. The laminates used in the project were based on 2/2 twill and unidirectional carbon prepregs. These were manufactured by either Resin Infusion (RI) or Vacuum Bagging (VB). Resin adjustments were made at the same time. The 2/2 twill and unidirectional carbon prepregs were first characterised by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Thermal Analysis (DMTA) before RI and VB. Dry 2/2 twill and unidirectional carbon fabrics and/or Resin Film (for VB) or fabrics and Epoxy Resin (for RI) were introduced in several plybooks and then cured. Final parts were either made of 2/2 twill carbon or unidirectional carbon. The parts were used to investigate the relationship between individual plies during the consolidation of a plybook. The first characterisations were done on flat laminates. Also two moulds were manufactured and used to produce new parts for further characterisations. The first, an aluminium mould was machined using a Computer Numerical Control (CNC). The second mould was a fan blade, made using chopped strand mats. The final parts had 3, 4 or 6 plies. These parts were characterised using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Torsion testing. The results provide a first step towards understanding how the friction at a ply/ply level can be influenced by the "starving" or the "enriching" of resin in a plybook during its consolidation. The work showed that in OOA manufacturing, the friction at a ply/ply level can be controlled by introducing Resin Film, Dry or Resin Rich Fabrics in a prepreg plybook. It was demonstrated that introducing lubrication to control ply friction during forming can result in quality part as high as that obtained from a traditional composite forming process. As the final parts were made using a fixed die mould and a vacuum bag, most of the plies in the layups could deform individually and accommodate interply shear. Torsion testing on a number of a random selection of samples showed negligible effects on shear stresses, strengths and modulus within the parts were negligible. It is argued that the flexibility of the vacuum bag could have had an impact on the layups during forming. The plies could conform to the mould easier. This work has potential for other applications. For example in match die moulding, introducing wet lubrication could improve interply shear during forming and help in improving accuracy and geometrical conformity of final parts. Furthermore, developing techniques to control friction during forming in OOA can be attractive to industries which could not afford to invest in this OOA prepreg technology. OOA processing times have become very attractive to industries such as the sporting good, automotive, wind energy and transportation. These industries could explore the opportunity presented by the work in this EngD thesis.

La mise en œuvre des préimprégnés unidirectionnels à fibre de carbone et résine époxyde est une étape fondamentale pour la conception de pièces structurales aéronautiques. Elle influe directement sur la qualité de la pièce et notamment sur la quantité de défauts poreux qu’elle renferme. Ainsi, deux phénomènes de création de la porosité ont été identifiés expérimentalement : l’un mécanique, l’autre thermodynamique. Une fois créés, ces défauts peuvent être extraits hors de la pièce si le marouflage et le cycle de polymérisation favorisent cette évacuation gazeuse. Les effets sur la porosité de la température et de la pression imposées pendant la réticulation de la résine sont modélisés en prenant en compte les phénomènes thermo-diffuso-mécaniques entre la résine et la bulle de gaz. Un protocole expérimental reposant sur l’analyse d’image a été développé afin de quantifier le plus précisément possible le taux volumique de porosité, ainsi que leurs tailles et leurs localisations. / Long fiber reinforced epoxy matrix composite laminate manufacturing process is divided into several stages. The most critical one is the polymerization stage. If not optimized, defects in the bulk material such as voids can occur. The aim of this work is to investigate the void formation and evolution processes in order to improve the thermoset laminates quality in minimizing the void ratio. Two phenomena causing void formation have been identified. The first is the mechanical entrapment of gas bubbles between prepreg plies during the lay up. Second is a thermodynamical one. Solvents and humidity absorbed by the prepreg during its manufacturing can be evaporated by increasing the temperature. Then, it has been shown that the vaccum bag lay up permeability in combination with the vaccum pressure could favour the gas washing out. In parallel, thermo-mechanical and diffusion models are coupled to obtain an accurate void size prediction along temperature and pressure applied during the polymerisation. In fact, these two parameters induce variations of the gas bubble radius inside resin. The first experimental results seem to validate qualitatively the calculated void size behaviour. Indeed, hydrostatic pressure imposed during polymerization plays a very important role on gas bubble shrinkage. Finally, a new experimental setup using image analyses has been developed to measure as accurate as possible the volume void ratio. Under specific conditions, stereology allows to extrapolate 2D results to 3D ones. Void ratios obtained with this method are in good agreement with acid digestion results. Complementary morphometric studies on void shapes have given new information about the heterogeneous void distribution in the specimen and also on the statistical void size distribution versus polymerization conditions.

The Master’s thesis deals with the design and production of a composite chassis of the new formula Dragon X. The carbon prepreg used for manufacturing of the monocoque was to be operated at high temperatures. Therefore, this thesis deals with the application of composites structures in the high temperature environment. The thesis addresses the torsional stiffness problematics and it was not only physically tested, but also simulated by FEM analysis and the results were compared.

The first part of the diploma thesis with name „Evaluation of dynamic damage of composite structure“ focuses on designing device for impact experiments and suitable laminate samples made from prepregs. The conditions and problems of impact tests are also demonstrated here. The second part of the thesis deals with non-destructive control of damaged specimens based on thermography. This is mainly the extent of defects in the impaired area and the evaluation of results using the pulse infrared thermography method. Finally, the relative deviation in the crack size comparison between the visual method and thermographic are compared. Consequently, the residual strength of the damaged samples against undamaged specimens are compared using bending tests.

In Its first half this master's thesis describes composite materials with carbon fiber reinforced plastics being the main focus point. An overview of production technologies follows. The major objective of the second part of this master's thesis is to design and manufacture a simplified model of an optical device using prepregs.

<p>In this doctoral thesis work, the impacts of alternative constituent material’s impact on low-cost prepreg manufacturing for high volume applications will be considered. Unidirectional prepregs offer the potential for significant increase of specific-properties and thereby weight savings. Hence the automotive industry is seeking to utilize composite components in their design, in order to meet new fuel economy ratings and global emissions targets imposed by governments. New resin formulations to achieve 3-minute cycle times or low-cost carbon fiber manufacturing have been created to address the needs of the automotive and other cost-sensitive industries, however these innovations have led to challenges in the composites manufacturing process. Quality control issues may include variations in resin saturation of the fiber bed, consolidation, porosity, and fiber volume fraction. These quality issues arise in the part forming step or from the initial resin infiltration during prepregging.</p> <p> </p> <p>Some low-cost carbon fiber has a kidney-bean shaped cross-section which has implications on the compaction and permeability of the fiber bed. The kidney-bean shaped fibers were shown in this work to follow a different compaction trend compared to circular fibers. Furthermore, these fibers required an order of magnitude larger force to compact than circular fibers to achieve similar fiber volume fraction, which had implications on the infiltration and consolidation step. A shape correction factor based on the fiber cross-sectional aspect ratio was proposed to extend the existing compaction model to fibers with irregular cross-sectional shapes. Additionally, permeability simulations were performed on the kidney-bean shaped carbon fiber in various fiber packing unit cells. Since the kidney-bean shaped fiber had some degree of asymmetry, there are two valid hexagonal packing arrangements. At a minimum, the hexagonal packed unit cell orientation caused a 17% reduction in permeability for the same unit cell and fiber volume fraction between the <u>+</u>90° and 0° orientations. In the most extreme case, a 47% reduction in the permeability was observed between the <u>+</u>90° and 0° orientations. Depending on the fiber orientation, comparable permeabilities to circular fibers were attained or up to a 74% reduction in permeability. This means a selection of low-cost carbon fiber could cause the infiltration time to be up to 3.86 longer than for a traditional carbon fiber.</p> <p> </p> <p>The low-cost carbon fiber was paired with a rapid cure epoxy resin which contained internal mold-release to further improve part cycle times to 3-minutes and reduce part costs. The effect of polar and non-polar internal mold-release was studied for its potential influence on cure kinetics. The polar internal mold-release caused a 20 second delay in the 3-minute part cycle, which increased the cycle time by 10% and would therefore influence part production schedules. This prepreg system was reported to have prepreg quality issues related to solids filtering during infiltration. A hot-melt prepregging process was modeled for S-wrap and nip-roller configurations. The S-wrap process was found to better suited for prepregging multi-phase resins since lower pressures were used. Additionally, a general rule was established when working with multi-phase resins was established, particle diameters should not exceed fiber radii.</p> <p> </p> <p>The general design principles from the thermoset hot-melt prepregging were used to develop a thermoplastic prepreg tape line. Thermoplastic composites lend themselves to efficient manufacturing processes such as hybrid overmolding which is suitable for the automotive industry. polyamide-66/Kevlar^® prepreg tapes were manufactured at various line tensions. Neat, rubber toughened, and glass bead filled polyamide-66 based resins were considered. The neat polyamide-66 resin provided a baseline and was able to consistently saturate the fiber bed up to 400µm regardless of manufacturing conditions. The addition of rubber particles did reduce the infiltration distances from the base resin by 20% with significant a significant 50% reduction when the fiber volume fraction reached 0.70. While the addition of glass particles significantly reduced the infiltration distances by up to 70% across all manufacturing conditions. The reduction in flow distance resulted in poor infiltration in thicker fiber beds.</p>

Since its beginnings, the aerospace industry has been interested in lowering the weight of aircraft. Moving from performance and economic drivers to environmental design parameters, the weight has continuously been a major focus for this industry. A possible option to reduce weight is to use lighter materials such as fibre reinforced polymer composites (FRPC). This type of material has the potential to be used into cold or moderate high-temperature sections of aero-engines. One major obstacle that hinders composite insertion into aero-engines is the lack of predictive models. In recent years, there has been increasing interest in multiscale modelling as a possible approach to reliably predict composite behaviour. This modelling refers to the simulation of a material’s behaviour through multiple scales, passing on information from one scale to another. The purpose of the present work is to use a commercially available software tool (Altair Multiscale Designer™) to virtually characterize an FRPC made from a non-crimp fabric reinforcement based on its individual constituent properties. The studied composite was a carbon fibre and epoxy system developed by GKN Aerospace. In order to achieve this, a well-characterized unidirectional (UD) carbon fibre prepreg composite was used to calibrate the software. After calibration and verification, different repetitive unit cells were created to capture the non-crimp fabric (NCF) architecture where the effect of fibre waviness was studied. The calibration step allowed for fairly accurate and acceptable results when testing unidirectional or ±45 laminates with different tested UD prepreg material systems. The higher deviation from experimental values was up to 20% with these laminates’ configurations. When simulating more complex layups, such as quasi-isotropic ones, the simulations resulted in over-predicting up to 40% of the composite strength in comparison to experimental data. The study of NCF composites appeared to be more complicated than anticipated. Their complex architecture exhibits complicated failure modes, which could not be captured by the software tool. Large inaccuracy up to 100% were observed between simulation and experimental values of the laminate strengths. In spite of its limitations, the study of NCF composites allowed for a deeper understanding of the software functionalities and findings on the fibre waviness impact onto the predicted stiffness, while the strength of the laminate did not show dependency with the fibre waviness.

The objective of this research was to explore and demonstrate the production andperformance of fiber-reinforced polymer (FRP) rebar manufactured on a continuous threedimensionalbraiding machine for use as reinforcement in concrete structures. Differentconfigurations of fiberglass/epoxy composite cylindrical rebar rods were manufactured,embedded in concrete, and tested in axial tension to identify the relationships betweenmanufacturing parameters and tensile pull-out strength of the rebar. The strength of the bondbetween concrete and FRP rebar was investigated using the pull-out test detailed by ACI 440.3R-12. The rebar was a No. 4 size and produced by combining multiple tows of fiberglass/epoxyprepreg to form the core of cylindrical rods which were consolidated using spirally-woundaramid consolidation fibers. The manufactured rebar was cured at 121°C (250°F) as specified bythe material manufacturer, TCR Composites. Preliminary research performed on carbon/epoxyrebar guided the process of developing a test matrix based on multiple variables. Primaryvariables investigated included the nature of the consolidation fiber material (dry vs prepreg),and the use of sand coating as a secondary process. The rebar samples were cast in 200 mm x200 mm x 200 mm (8.0 in x 8.0 in x 8.0 in) concrete cubes to investigate bond strength. A testfixture was designed and fabricated for use on a universal tensile testing machine. Standard 12.7mm (0.5 in) diameter steel rebar and a commercially comparable fiberglass rebar were alsotested to provide baseline values. Measurements were collected at both the free and loaded endsof the rebar with free-end results being a more accurate presentation of rebar bond stress.Results showed that the bond strength was 6-13% higher for the free-end for rebarconsolidated with a dry tow compared to prepreg tow consolidated rebar. When sand was added,dry tow consolidated sand-coated samples showed higher bond stress in the range of 15-26% forthe free-end than samples consolidated with a dry tow but excluded sand coating. Samplesconsolidated with prepreg tow and coated with sand showed higher bond stress in the range of43-58% for the free-end compared to prepreg tow no-sand coating samples. Overall, for therebar manufactured on the 3-D braiding machine, the prepreg tow consolidated rebar samplesrecorded the highest bond strength values with a maximum average bond stress value of 15.2MPa (2.26 ksi). The dry tow sand consolidated rebar recorded a maximum average bond stressvalue of 11.4 MPa (1.65 ksi). The rebar purchased from American Fiberglass Rebar recorded amaximum average bond stress of 12.0 MPa (1.74 ksi) while the maximum average bond stress ofsteel rebar was 13.1 MPa (1.90 ksi). Results demonstrated that quality composite rebar can bemanufactured using the 3-D braiding machine and that consolidating the rebar with a prepregtow and coating the surface with sand resulted in a rebar which bonded well with concretecompared to commercialized FRP and steel rebar.

The objective of this research was to explore and demonstrate the production andperformance of fiber-reinforced polymer (FRP) rebar manufactured on a continuous threedimensionalbraiding machine for use as reinforcement in concrete structures. Differentconfigurations of fiberglass/epoxy composite cylindrical rebar rods were manufactured,embedded in concrete, and tested in axial tension to identify the relationships betweenmanufacturing parameters and tensile pull-out strength of the rebar. The strength of the bondbetween concrete and FRP rebar was investigated using the pull-out test detailed by ACI 440.3R-12. The rebar was a No. 4 size and produced by combining multiple tows of fiberglass/epoxyprepreg to form the core of cylindrical rods which were consolidated using spirally-woundaramid consolidation fibers. The manufactured rebar was cured at 121C (250F) as specified bythe material manufacturer, TCR Composites. Preliminary research performed on carbon/epoxyrebar guided the process of developing a test matrix based on multiple variables. Primaryvariables investigated included the nature of the consolidation fiber material (dry vs prepreg),and the use of sand coating as a secondary process. The rebar samples were cast in 200 mm x200 mm x 200 mm (8.0 in x 8.0 in x 8.0 in) concrete cubes to investigate bond strength. A testfixture was designed and fabricated for use on a universal tensile testing machine. Standard 12.7mm (0.5 in) diameter steel rebar and a commercially comparable fiberglass rebar were alsotested to provide baseline values. Measurements were collected at both the free and loaded endsof the rebar with free-end results being a more accurate presentation of rebar bond stress.Results showed that the bond strength was 6-13% higher for the free-end for rebarconsolidated with a dry tow compared to prepreg tow consolidated rebar. When sand was added,dry tow consolidated sand-coated samples showed higher bond stress in the range of 15-26% forthe free-end than samples consolidated with a dry tow but excluded sand coating. Samplesconsolidated with prepreg tow and coated with sand showed higher bond stress in the range of43-58% for the free-end compared to prepreg tow no-sand coating samples. Overall, for therebar manufactured on the 3-D braiding machine, the prepreg tow consolidated rebar samplesrecorded the highest bond strength values with a maximum average bond stress value of 15.2MPa (2.26 ksi). The dry tow sand consolidated rebar recorded a maximum average bond stressvalue of 11.4 MPa (1.65 ksi). The rebar purchased from American Fiberglass Rebar recorded amaximum average bond stress of 12.0 MPa (1.74 ksi) while the maximum average bond stress ofsteel rebar was 13.1 MPa (1.90 ksi). Results demonstrated that quality composite rebar can bemanufactured using the 3-D braiding machine and that consolidating the rebar with a prepregtow and coating the surface with sand resulted in a rebar which bonded well with concretecompared to commercialized FRP and steel rebar.