High-performance yarns such as aramid fibers are nowadays used to reinforce composite materials due to their advantageous physico-chemical properties and their low weight. They are also resistant to heat and fire. Para-aramid filament yarns (p-AFs) wound on a cylindrical dyeing package have been silvered successfully by means of a newly developed wetchemical filament yarn metallization process on a laboratory scale. The surface morphology of untreated and silvered p-AF was determined by means of scanning electron microscopy. The chemical structure of the surfaces (contents of carbon, oxygen, nitrogen and silver) was determined by means of energy-dispersive X-ray spectroscopy (EDX). The eliminated and newly formed groups of p-AF before and after silvering were detected by infrared spectroscopy (Fourier transform—attenuated total reflectance). After metallization, the silver layer thickness, the mass-related silver content and washing and rubbing fastness were assessed. Furthermore, textile-physical examinations concerning Young’s modulus, elongation at break and electrical conductivity were performed. Subsequently, the electrically conductive p-AFs were integrated in thermoset composite materials reinforced by glass fibers and para-aramid.

I dagsläget är de flesta broar i Sverige tillverkade med betong eller stål. Dessa broar är många gånger förknippade med stora kostnader som ofta beror på underhåll och reparation. FRP, som står för Fiber Reinforced Polymer, är ett relativt nytt material i bärande stommar men är ett väl etablerat material i förstärkningssammanhang. I Europa och i synnerhet Nederländerna finns det flertal broar byggda i FRP. Men på grund av brist på normer och regelverk att luta sig emot sker det sällan någon form av brokonstruktion med FRP i Sverige. Detta examensarbete syftar till att undersöka befintliga normer och studera hur materialet FRP används vid förstärkning och konstruktion av broar. Vidare syftar även arbetet till att undersöka egenskaperna hos FRP som byggmaterial och jämföra det med konventionella material som stål och betong. FRP, också benämnd fiberkomposit, är ett kompositmaterial som kan sammanställas på flera olika sätt. Genom olika material som kombineras och olika tillverkningsprocesser som används kan man på så sätt ge individuell utformning till materialet för dess användning. Fördelarna med FRP är många, men i allmänhet har det god styrka, god beständighet samtidigt som det har en låg vikt. Detta resulterar i att inom brokonstruktion så ger det strukturen en minskad egenvikt, vilket i sin tur underlättar en mängd olika saker. Detta arbete visar på att FRP-material har fördelaktiga egenskaper och kan i vissa situationer vara mer gynnsamt att använda än stål eller betong. Dock som tidigare påpekat saknas det specifika Eurokoder för detta material. Däremot är vi säkra på att introduktionen av en ny Eurokod samt med uppmuntran från myndigheter kommer användningen av FRP inom brokonstruktion utan tvekan öka. / At present, most bridges in Sweden are made with concrete or steel. These bridges are often associated with high costs, which often depend on maintenance and repair. FRP, which stands for Fiber Reinforced Polymer, is a relatively new material in load-bearing structures but is a well- established material in the context of reinforcement. In Europe and in particular the Netherlands, there are several bridges built in FRP. But due to a lack of norms and regulations to lean against, there is rarely any kind of FRP bridge construction in Sweden. The aim of this thesis is to examine existing norms and study how the material FRP is used in the reinforcement and construction of bridges. Furthermore, this thesis also aims to investigate the properties of FRP as building material and compare it with conventional materials such as steel and concrete. FRP, also called fiber-composite, is a composite material that can be assembled in several different ways. Through various materials that are combined and different manufacturing processes used, one can thus provide individual designs for the material. The benefits of FRP are many, but generally it has good strength, good durability while having a low weight. This results in that within bridge construction, it gives the structure a reduced self-weight, which in turn facilitates a variety of things. This thesis shows that FRP materials have advantageous properties and in some situations can be more favorable to use than steel or concrete. However, as previously pointed out, there are no specific Eurocodes for this material. However we are sure that the introduction of a new Eurocode and encouragement from authorities will undoubtedly increase the use of FRP in bridge construction.

Achieving light weight armor design has become an important engineering challenge in the last three decades. As weapons becoming highly sophisticated, so does the ammunition, potential targets have to be well protected against such threats. In order to provide mobility, light and effective armor protection materials should be used. In this thesis, numerical simulation of the silicon carbide armor backed by KevlarTM composite and orthogonally impacted by 7.62mm armor piercing (AP) projectile at an initial velocity of 850 m/s is analyzed by using AUTODYN hydrocode. As a first step, ceramic material behavior under impact conditions is validated numerically by comparing the numerical simulation result with the test result which is obtained from the literature. Then, different numerical simulations are performed by changing the backing material thickness, i.e. 2, 4, 6 and 8mm, while the thickness of the ceramic is held constant, i.e. 8mm. At the end of the simulations, optimum ceramic/composite thickness ratio is sought. The results of the simulations showed that for the backing thickness values of 4, 6 and 8mm, the projectile could not perforate the armor system. On the contrary, the projectile could penetrate and perforate the armor system for the backing thickness value of 2mm and it has still some residual velocity. From these results, it is inferred that the optimum ceramic/composite thickness ratio is equal to about 2 for the silicon carbide and kevlar configuration.

This thesis reports on a design study, conducted for an advanced composite helmet shell for helicopter pilots. The helmet shell is expected to provide a level of protection against low velocity impacts with its weight criteria. Therefore, ergonomy, light weight, and the ability to withstand low velocity impact became the main issues for this study. For this purpose, an experimental program has been developed including low velocity impact tests on specimens. The drop height, drop weight, specimen stacking sequences and size were constant parameters. Test specimens were produced using the plate size of 220x220 mm having different thicknesses. Specimen materials were aramid, carbon, and a hybrid form of these two. Thus, the parameters of the study were specimen thickness and the material types. The impact tests are carried out on a specially designed test rig. The design decisions are made in accordance with the results of the experiments. In compliance with the lightweight and manufacturing criteria, the hybrid specimen was selected helmet shell. For the purpose of ergonomy a geometric design was also conducted from headfrom sizes of Turkish Army by using 3D design software. After specifying the composite material, manufactured helmet shell was tested in another test rig according to the ANSI Z90.1.1992. For the requirement of the acceleration level 300g, the helmet shell design was found to be successful at seven different and critical impact points.

Flammable solvents contained in liquid electrolytes pose a serious safety risk when used in lithium batteries. Oxide ceramic electrolytes are a safer alternative, but suffer from inadequate mechanical properties and ionic conductivity. Thin electrolyte layers resolve the issue of conductance, but accentuate the detrimental mechanical properties of oxide ceramics. The presented work has investigated oxide ceramic electrolyte reinforcement in composite electrolytes for all-solid-state batteries. Fabricating oxide ceramic electrolytes with engineered microstructure enabled development of a reinforced composite. This approach is based on the formation of 3D- porous ceramics via stereolithography printing of polymer templates from designed cubic, gyroid, diamond and bijel architectures. The microstructural parameters of templates were analysed and modified using computational techniques. Infiltration of the prepared 3D-porous electrolyte with polymeric-fibre reinforcement created the reinforced composite electrolyte. The prepared ceramic composite showed excellent reproduction of the template microstructure, good retention of ionic conductivity and enhanced mechanical properties. The final composite was composed of NASICON-type Li_1.6Al_0.6Ge_1.4(PO₄)₃ oxide ceramic electrolyte and epoxy and aramid fibre reinforcement. The gyroid architecture was computationally determined as having the optimal stress transfer efficiency between two phases. The printed gyroid polymer template gave excellent pore microstructure reproduction in ceramic that had 3D-interconnected porosity, high relative density and the most uniform thickness distribution. The ceramic matrix porosity allowed for complete infiltration of reinforcement by aramid and epoxy forming the fibre-reinforced ceramic matrix composite. The interpenetrating composite microstructure with ceramic and epoxy gave a flexural strength increase of 45.65 MPa compared to the ceramic. Unfortunately, the infiltration procedure of aramid-epoxy reinforcement did not realise the full tensile strength potential of aramid fibres.

Nos últimos anos o conhecimento do comportamento de estruturas de concreto armado reforçadas com materiais compósitos aumentou significativamente, devido aos esforços em pesquisa induzidos pelo crescente interesse da indústria da construção.Todavia, precisam ser mais bem investigadas questões relativas à ligação concreto-reforço, assim como a durabilidade e a resposta ao longo do tempo de estruturas reforçadas. Buscando colaborar neste sentido, o objetivo principal desta tese foi estudar os mecanismos de falha prematura, devido ao carregamento cíclico ao efeito da concentração de tensão no compósito na região de fissuração do concreto. O comportamento da ligação foi estudado simulando experimentalmente situações de fissuração por flexão e cisalhamento, separadamente. Os resultados não confirmaram a hipótese de que os deslocamentos diferenciais na borda de uma fissura geram esforços de cisalhamento que provocam primeiramente a ruptura do compósito, indicando que o principal problema pode ser deformações localizadas. Confirmaram, porém, a importância de ancoragens adicionais e indicaram que o comprimento de ancoragem necessário nos compósitos não é muito elevado, aproximadamente 200mm. Já a influência do carregamento cíclico foi estudada em dois grupos de vigas, de tamanho reduzido e em escala real, submetidas a diferentes níveis de variação da tensão (20% a 70%) e tensão mínima (10% a 40%), no intuito de obter informações do comportamento à fadiga em diversas circunstâncias. Compósitos formados com fibras de vidro e aramida foram testados como alternativas de menor custo, além do carbono. Os resultados mostraram que o comportamento à fadiga dos diferentes compósitos varia, com vantagem para o PRF de carbono. A falha por fadiga é governada pela fratura das barras de aço, mas a presença do reforço aumenta a vida útil, não só reduzindo a tensão na armadura mas também retardando a falha. A presença do reforço, especialmente quando são usadas diversas camadas de fibras, parece contribuir para o retardamento da falha por fadiga, devido ao controle do processo de fissuração. Os resultados permitiram criar modelos de regressão linear para previsão da resistência à fadiga, para vigas reforçadas e não reforçadas, que se ajustaram bem aos dados de vários pesquisadores em comparação a outros modelos. O modelo proposto indica que quando são aplicadas tensões altas, a falha por fadiga pode ocorrer primeiramente no compósito ou na interface. Estudos adicionais, para caracterizar o comportamento à fadiga de estruturas reforçadas com PRF quando as tensões ou variações no reforço são elevadas e para confirmar se o limite à fadiga dos PRF realmente se localiza em torno de uma variação de tensão de 200MPa, valor superior ao recomendado pelo ACI 215R (150MPa). / Knowledge about the behavior of RC structures strengthened with fiber reinforced polymers has significantly increased in the last few years, due to a strong research effort induced by a growing interest from practitioners. Nonetheless, there are still some important issues regarding the behavior of these materials that require attention, such as characterization of premature failure mechanisms, durability requirements and long time response under load. The main objective of this study was to analyze failure mechanisms related to fatigue due to cyclic loads and tension concentration in the composite in regions of cover concrete cracking. The bonding behavior in regions where the cover concrete was cracked was studied by experimental simulation of flexural and shear cracking, separately. The results did not confirm the initial hypothesis that crack tip differential displacements induce shear stresses that produce early composite failure, indicating that the main problem was probably due to localized tensile strain. The data collected, however, highlighted the importance of using additional anchorage laces and suggested that the effective anchorage length of a PRF is approximately 200mm. The effects of cyclic loads was investigated in real scale and reduced size beams, subjected to different levels of stress variation (20% to 70%) and distinct values of minimum stress (10% to 40%), in order to gather information about behavior under various circumstances. Glass and aramid fiber composites were tested as lower cost reinforcement alternatives. The results showed that the fatigue behavior of different composites varies, with CFRP having the best performance. Failure is normally controlled by the fatigue of the steel bars, but the presence of the reinforcement reduces the stress levels in the steel and increases fatigue service life considerably. The presence of the reinforcement, especially when multi-layered, also seems to delay the fatigue failure due to cracking control. Regression models were developed to predict the fatigue service life of strengthened beams that had a better fit to experimental data collected in this work and by other researchers than other models tested. The model suggests that when high stresses are applied, fatigue might occur first in the composite or the bonding interface. Additional work is required to confirm the indication that the fatigue limit of strengthened beams is associated with a stress level of 200MPa in the rebar, higher than the recommended value (150 MPa) used in the ACI design guideline 215R.

Nos últimos anos o conhecimento do comportamento de estruturas de concreto armado reforçadas com materiais compósitos aumentou significativamente, devido aos esforços em pesquisa induzidos pelo crescente interesse da indústria da construção.Todavia, precisam ser mais bem investigadas questões relativas à ligação concreto-reforço, assim como a durabilidade e a resposta ao longo do tempo de estruturas reforçadas. Buscando colaborar neste sentido, o objetivo principal desta tese foi estudar os mecanismos de falha prematura, devido ao carregamento cíclico ao efeito da concentração de tensão no compósito na região de fissuração do concreto. O comportamento da ligação foi estudado simulando experimentalmente situações de fissuração por flexão e cisalhamento, separadamente. Os resultados não confirmaram a hipótese de que os deslocamentos diferenciais na borda de uma fissura geram esforços de cisalhamento que provocam primeiramente a ruptura do compósito, indicando que o principal problema pode ser deformações localizadas. Confirmaram, porém, a importância de ancoragens adicionais e indicaram que o comprimento de ancoragem necessário nos compósitos não é muito elevado, aproximadamente 200mm. Já a influência do carregamento cíclico foi estudada em dois grupos de vigas, de tamanho reduzido e em escala real, submetidas a diferentes níveis de variação da tensão (20% a 70%) e tensão mínima (10% a 40%), no intuito de obter informações do comportamento à fadiga em diversas circunstâncias. Compósitos formados com fibras de vidro e aramida foram testados como alternativas de menor custo, além do carbono. Os resultados mostraram que o comportamento à fadiga dos diferentes compósitos varia, com vantagem para o PRF de carbono. A falha por fadiga é governada pela fratura das barras de aço, mas a presença do reforço aumenta a vida útil, não só reduzindo a tensão na armadura mas também retardando a falha. A presença do reforço, especialmente quando são usadas diversas camadas de fibras, parece contribuir para o retardamento da falha por fadiga, devido ao controle do processo de fissuração. Os resultados permitiram criar modelos de regressão linear para previsão da resistência à fadiga, para vigas reforçadas e não reforçadas, que se ajustaram bem aos dados de vários pesquisadores em comparação a outros modelos. O modelo proposto indica que quando são aplicadas tensões altas, a falha por fadiga pode ocorrer primeiramente no compósito ou na interface. Estudos adicionais, para caracterizar o comportamento à fadiga de estruturas reforçadas com PRF quando as tensões ou variações no reforço são elevadas e para confirmar se o limite à fadiga dos PRF realmente se localiza em torno de uma variação de tensão de 200MPa, valor superior ao recomendado pelo ACI 215R (150MPa). / Knowledge about the behavior of RC structures strengthened with fiber reinforced polymers has significantly increased in the last few years, due to a strong research effort induced by a growing interest from practitioners. Nonetheless, there are still some important issues regarding the behavior of these materials that require attention, such as characterization of premature failure mechanisms, durability requirements and long time response under load. The main objective of this study was to analyze failure mechanisms related to fatigue due to cyclic loads and tension concentration in the composite in regions of cover concrete cracking. The bonding behavior in regions where the cover concrete was cracked was studied by experimental simulation of flexural and shear cracking, separately. The results did not confirm the initial hypothesis that crack tip differential displacements induce shear stresses that produce early composite failure, indicating that the main problem was probably due to localized tensile strain. The data collected, however, highlighted the importance of using additional anchorage laces and suggested that the effective anchorage length of a PRF is approximately 200mm. The effects of cyclic loads was investigated in real scale and reduced size beams, subjected to different levels of stress variation (20% to 70%) and distinct values of minimum stress (10% to 40%), in order to gather information about behavior under various circumstances. Glass and aramid fiber composites were tested as lower cost reinforcement alternatives. The results showed that the fatigue behavior of different composites varies, with CFRP having the best performance. Failure is normally controlled by the fatigue of the steel bars, but the presence of the reinforcement reduces the stress levels in the steel and increases fatigue service life considerably. The presence of the reinforcement, especially when multi-layered, also seems to delay the fatigue failure due to cracking control. Regression models were developed to predict the fatigue service life of strengthened beams that had a better fit to experimental data collected in this work and by other researchers than other models tested. The model suggests that when high stresses are applied, fatigue might occur first in the composite or the bonding interface. Additional work is required to confirm the indication that the fatigue limit of strengthened beams is associated with a stress level of 200MPa in the rebar, higher than the recommended value (150 MPa) used in the ACI design guideline 215R.

Nos últimos anos o conhecimento do comportamento de estruturas de concreto armado reforçadas com materiais compósitos aumentou significativamente, devido aos esforços em pesquisa induzidos pelo crescente interesse da indústria da construção.Todavia, precisam ser mais bem investigadas questões relativas à ligação concreto-reforço, assim como a durabilidade e a resposta ao longo do tempo de estruturas reforçadas. Buscando colaborar neste sentido, o objetivo principal desta tese foi estudar os mecanismos de falha prematura, devido ao carregamento cíclico ao efeito da concentração de tensão no compósito na região de fissuração do concreto. O comportamento da ligação foi estudado simulando experimentalmente situações de fissuração por flexão e cisalhamento, separadamente. Os resultados não confirmaram a hipótese de que os deslocamentos diferenciais na borda de uma fissura geram esforços de cisalhamento que provocam primeiramente a ruptura do compósito, indicando que o principal problema pode ser deformações localizadas. Confirmaram, porém, a importância de ancoragens adicionais e indicaram que o comprimento de ancoragem necessário nos compósitos não é muito elevado, aproximadamente 200mm. Já a influência do carregamento cíclico foi estudada em dois grupos de vigas, de tamanho reduzido e em escala real, submetidas a diferentes níveis de variação da tensão (20% a 70%) e tensão mínima (10% a 40%), no intuito de obter informações do comportamento à fadiga em diversas circunstâncias. Compósitos formados com fibras de vidro e aramida foram testados como alternativas de menor custo, além do carbono. Os resultados mostraram que o comportamento à fadiga dos diferentes compósitos varia, com vantagem para o PRF de carbono. A falha por fadiga é governada pela fratura das barras de aço, mas a presença do reforço aumenta a vida útil, não só reduzindo a tensão na armadura mas também retardando a falha. A presença do reforço, especialmente quando são usadas diversas camadas de fibras, parece contribuir para o retardamento da falha por fadiga, devido ao controle do processo de fissuração. Os resultados permitiram criar modelos de regressão linear para previsão da resistência à fadiga, para vigas reforçadas e não reforçadas, que se ajustaram bem aos dados de vários pesquisadores em comparação a outros modelos. O modelo proposto indica que quando são aplicadas tensões altas, a falha por fadiga pode ocorrer primeiramente no compósito ou na interface. Estudos adicionais, para caracterizar o comportamento à fadiga de estruturas reforçadas com PRF quando as tensões ou variações no reforço são elevadas e para confirmar se o limite à fadiga dos PRF realmente se localiza em torno de uma variação de tensão de 200MPa, valor superior ao recomendado pelo ACI 215R (150MPa). / Knowledge about the behavior of RC structures strengthened with fiber reinforced polymers has significantly increased in the last few years, due to a strong research effort induced by a growing interest from practitioners. Nonetheless, there are still some important issues regarding the behavior of these materials that require attention, such as characterization of premature failure mechanisms, durability requirements and long time response under load. The main objective of this study was to analyze failure mechanisms related to fatigue due to cyclic loads and tension concentration in the composite in regions of cover concrete cracking. The bonding behavior in regions where the cover concrete was cracked was studied by experimental simulation of flexural and shear cracking, separately. The results did not confirm the initial hypothesis that crack tip differential displacements induce shear stresses that produce early composite failure, indicating that the main problem was probably due to localized tensile strain. The data collected, however, highlighted the importance of using additional anchorage laces and suggested that the effective anchorage length of a PRF is approximately 200mm. The effects of cyclic loads was investigated in real scale and reduced size beams, subjected to different levels of stress variation (20% to 70%) and distinct values of minimum stress (10% to 40%), in order to gather information about behavior under various circumstances. Glass and aramid fiber composites were tested as lower cost reinforcement alternatives. The results showed that the fatigue behavior of different composites varies, with CFRP having the best performance. Failure is normally controlled by the fatigue of the steel bars, but the presence of the reinforcement reduces the stress levels in the steel and increases fatigue service life considerably. The presence of the reinforcement, especially when multi-layered, also seems to delay the fatigue failure due to cracking control. Regression models were developed to predict the fatigue service life of strengthened beams that had a better fit to experimental data collected in this work and by other researchers than other models tested. The model suggests that when high stresses are applied, fatigue might occur first in the composite or the bonding interface. Additional work is required to confirm the indication that the fatigue limit of strengthened beams is associated with a stress level of 200MPa in the rebar, higher than the recommended value (150 MPa) used in the ACI design guideline 215R.

Manufacturing more reliable and lighter body armour using the fabrics with high-performance fibres is the development trend of ballistic protection device. However,increasing the reliability of the body armour normally needs to increase weight. Thisinvestigation aims to develop better ballistic performance of body armour withoutaffecting weight. Inter-yarn friction in quasi-static state in fabrics constructed for bodyarmour is one of the important factors affecting ballistic performance. This researchfocuses on increasing inter-yarn friction by surface modification methods for superiorballistic protection of woven fabrics. Finite element (FE) simulation is employed toanalyse the effects of inter-yarn friction on ballistic performance theoretically. BothAPPCVD and sol-gel methods are used to achieve the purpose of practically increasinginter-yarn friction. Ballistic experiments are conducted to evaluate ballistic performanceof the fabrics with different levels of inter-yarn friction after treatments. Through both numerical and experimental investigation, it is confirmed that increasinginter-yarn friction in quasi-static state can improve ballistic performance of fabrics. Theoverall energy absorption will be increased with the increase of inter-yarn frictionbecause higher inter-yarn friction generates higher resistance to the projectile, makesfabric structure more stable, leads to more involvement of the secondary yarns andincreases both KE and FDE percentages. Moreover, higher levels of inter-yarn frictionwill flatten the trauma and make the fabric response more globalised owing to the lesstransverse deflection ability. However, over high inter-yarn friction is counterproductivebecause of stress concentration on the primary yarns. For the surface modification, one of the aramid yarns, Twaron® yarn and one of theUHMWPE yarns, Dyneema® yarn, and their fabric products are used as the substrates. SEM analyses are used to characterise the morphology changes. Both FTIR and EDXanalyses are conducted to identify the coated substance. Based on coefficients of friction test and yarn pull-out test, the APPCVD treatment and sol-gel treatment have been proved as two effective ways to increase inter-yarn friction and at the same time the tensile properties of the yarns and the weight are almost unaffected. Moreover, sol-gel treatment has been established as an effective method for improvingballistic performance without significant weight increase, where the energy absorption ofthe Dyneema® fabric can be increased by 6.74%, and the trauma depth can be decreased by16.99% for Twaron® fabric panel and by10.73% for Dyneema® fabric panel.

Unidirectional carbon fiber and fiberglass epoxy composite elements consolidated with aramid sleeves were radially impacted at 5 J (3.7 ft-lbs) and 10 J (7.4 ft-lbs), tested under compression, and compared to undamaged control specimens. These structural elements represent local members of open three-dimensional composite lattice structures (e.g., based on isogrid or IsoTruss® technologies). Advanced three-dimensional braiding techniques were used to continuously fabricate these specimens. The unidirectional core specimens, 8 mm (5/16 in) in diameter, were manufactured with various sleeve patterns. Bi-directional braided sleeves and unidirectional spiral sleeves ranged from a nominal full to half coverage. These specimens were tested for compression strength after impact. This research used an unsupported length of 50.8 mm (2.0 in) specimens to ensure a strength-controlled compression failure. Compression strength of undamaged unidirectional carbon fiber and fiberglass epoxy composites is virtually unaffected by sleeve type and sleeve coverage. Fiberglass/epoxy configurations exhibited approximately 1/2 and 2/3 reduction in compression strength relative to undamaged configurations after impact with 5 J (3.7 ft-lbs) and 10 J (7.4 ft-lbs), respectively. Increasing aramid sleeve coverage and/or increasing the interweaving of an aramid sleeve (i.e., braid vs. spiral) increases the damage tolerance of fiberglass/epoxy composite elements. Damaged carbon/epoxy composites exhibited an approximate decrease in strength of 70% and 75% after 5 J and 10 J of impact, respectively, relative to undamaged configurations. The results verify that an aramid sleeve, regardless of type (braid or spiral), facilitates consolidation of the carbon fiber and fiberglass epoxy core. Not surprisingly, full coverage configurations exhibit greater compression strength after impact than half coverage configurations.