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Item type:Publication, Access status: without files , The influence of residual stresses implicated via cure volume shrinkage on CF/VEUH-composites(2006-01); ; ; This paper presents a thermal finite element analysis (FEA) of a unidirectional carbon fibre reinforced vinylester urethane hybrid matrix system. The evolution of the thermal residual stresses due to the mismatch in the coefficient of thermal expansion (CTE) of the single components in the cooling phase have been investigated. Additionally, the cure volume shrinkage was implemented into the FE-model. The model allows the transition of the homogeneous unidirectional composite material properties on a microscopic spot, where the properties of the fibres and the matrix can be considered separately. It could be shown, that the cure volume shrinkage (CVS) has a dramatic effect on the fibre/matrix interface region due to radial compression stresses along the fibre. Further, this may lead to microcracking or fibre/matrix debonding before any kind of load is applied to the material.Publicationtype: Journal Article12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Design and fabrication of an on-line consolidation facility for thermoplastic compositesAn experimental apparatus that utilizes continuous fiber reinforced thermoplastics to wind rings and short tubes has been developed. Termed an on-line consolidation facility, preimpregnated tow is consolidated while the ring is being wound. The three most important parameters for the consolidation process are time, temperature, and pressure, and the facility is designed to establish their optimum combination. Therefore, each component of the apparatus provides maximum flexibility and variability in terms of these parameters. This article describes the basic concept of the process and then shows how the concept can be realized. The technique for heating the impregnated tow utilizes infrared radiation. However, additional heat sources are used to provide optimum temperature control at the nip point. Finally, several types of preimpregnated tow are used to produce samples that prove the feasibility of the process and establish acceptable ranges on the parameters.Publicationtype: Journal Article237 705 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Interlaminar Fracture Energy of Laminates Made of Thermoplastic Impregnated Fiber BundlesInterlaminar mode I- and II-fracture energy measurements (in terms of the strain energy release rate) were carried out with different laminates of a glass fiber/thermoplastic PA 12- and aramid fiber/PA 12-composite system. Specimens were prepared from fiber bundles interspersed with polymer powder and a polymer sheath around them. The results, obtained from two different test procedures and data reduction methods, reflect a good interlaminar fracture toughness of the different laminates. This can be attributed to the large damage zone size due to the tough matrix and a big amount of fiber bridging, which is highlighted by micrographs achieved with SEM-analysis.Publicationtype: Journal Article234 477 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Fracture toughness of short fiber/thermoplastic matrix composites, compared on the basis of different test methods(1988-01-01); ; ; A variety of thermoplastic matrices, including Polyethersulfone (PES), Polyoxymethylene (POM), and toughness modified Polyethylenterephthalate (PET), and their short glass fiber reinforced composites have been tested with respect to their impact resistance. Test methods applied, all characterize in some respects the "toughness" of these materials. It turns out, however, that the ranking order of their toughnesses varies quite remarkably, depending on the particular testing procedure. In a fracture mechanics test with compact tension specimens, the fracture toughness of Polyethersulfone, for instance, is very low compared to the other thermoplastics and to their short fiber reinforced versions. This is due to the very sharp notches used in this kind of toughness test, and due to the high notch sensitivity of PES. In a falling dart test with a CEAST® modular falling weight device, and the use of unnotched plates, PES proves to be, on the other hand, much better than all the other competitive materials. The results are discussed with respect to the content of infor mation of the individual tests on the "toughness" profile of the different polymers and com posite materials studied.Publicationtype: Journal Article254 421