Design, manufacture and evaluation of partially-cured composite materials
- Autores: Vanesa Martínez Serrano
- Directores de la Tesis: Carlos González Martínez (dir. tes.)
- Lectura: En la Universidad Carlos III de Madrid ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Jon Mikel Molina Aldareguia (presid.), Álvaro Ridruejo (secret.), Claudio Saul Lopes (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia e Ingeniería de Materiales por la Universidad Carlos III de Madrid
- Materias:
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- Resumen
Typically, the manufacture of high-performance composite materials by autoclave with the use of prepregs and with the joint application of high pressures and temperatures, thus reducing the porosity of the material guaranteeing good mechanical properties. However, this manufacturing system involves long production times and large investments in equipment, resulting in increased demand for alternative manufacturing systems. This thesis shows the experimental procedures to develop a processing route for the manufacture of partially-cured composite materials capable of being post-cured and consolidated with their traditional fresh counterparts with the aim of producing integrated structures one-shot, thus reducing costs and time. Partially-cured materials were manufactured from dry carbon fabrics and epoxy resin using the Vacuum assisted Resin Transfer Moulding (VaRTM) process. The glass transition temperature, Tg, of the partially-cured material must be within two limits. On the one hand, the glass transition temperature should be high enough to keep the sticky and deformity within an acceptable range. On the other hand, the glass transition temperature should be sufficiently low to provide a good adaptability of the composite material in the later post-cure cycle. The homogeneity of the mould temperature was crucial to reach the specific degrees of curing needed for subsequent integration. For this purpose, two moulds were designed, one flat and the other in T-shape, both equipped with a number of independent resistances to allow a detailed control of the temperature of the composite material. The exothermic reaction of the epoxy resin was controlled according to the specific curing cycle. The curing cycle was determined on the basis of some tests carried out on samples taken from the partially-cured material using Differential Scanning Calorimetry (DSC) and Mechanical-Dynamic Analysis (DMA). Following this procedure, it will be possible to manufacture final materials in a standard (for example, support) way with a homogeneous degree of curing. The manufactured materials were stored cold as is the case with the standard prepregs before subsequent integration with fresh and cured prepregs skins. Ensuring an adequate degree of curing is the key to this work, as well as ensuring that the partially-cured material was able to adapt to the different geometries of the skin maintaining the geometry of the manufactured material and without effect from the resin bleeding of the material partially-cured. With this our objective of producing integrated structures one-shot, thus reducing costs and time in the autoclave manufacturing process was fulfilled.
