María Martín

Bio: María Martín is an academic researcher from Technical University of Madrid. The author has contributed to research in topics: Social class & Lamination (topology). The author has an hindex of 5, co-authored 10 publications receiving 88 citations.

Effect of processing parameters and void content on mechanical properties and NDI of thermoplastic composites

Abstract: Several consolidation cycles were performed to study the impact of processing parameters on void content, ultrasonic NDT and mechanical performance of CF/PEEK composites. A series of [+45/−45]4S laminates were manufactured by out-of-autoclave technologies including vacuum bag only, hot-press, and automatic lay-up with in-situ consolidation. A range of porosity between 0 and 19% of void content was assessed by varying the processing temperature from 340 to 500 °C and pressure from 0.25 to 1.5 MPa. Void content, shape and location were characterized by using C-scan, matrix digestion and 2D microscopy. Mechanical characterization including in-plane shear and interlaminar shear testing was performed. The results show a critical void content where properties start to decrease at a given drop-off rate. The results suggest that each processing technology should have its own quality control criteria. The proposed methodology is useful for engineering applications of thermoplastic composites and the creation of NDT acceptance criteria.

On the determination of thermal degradation effects and detection techniques for thermoplastic composites obtained by automatic lamination

Abstract: Automatic lay-up and in-situ consolidation with thermoplastic composite materials is a technology under research for its expected use in the profitable manufacturing of structural aeronautical parts. This study is devoted to analysing the possible effects of thermal degradation produced by this manufacturing technique. Rheological measurements showed that there is negligible degradation in PEEK for the temperatures reached during the process. Thermogravimetric analysis under linear heating and constant rate conditions show that thermal degradation is a complex process with a number of overlapping steps. A general kinetic equation that describes the degradation of the material with temperature has been proposed and validated. Attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed that there is no remarkable degradation. The use of a combination of in-situ and ex-situ experimental techniques, including kinetic modelling, not only provides reliable information about degradation but also allows setting optimal processing conditions.

Diferencias de género en los hábitos de actividad física de la población adulta en la Comunidad de Madrid

Abstract: La investigacion persigue contrastar la hipotesis de la existencia de dos diferentes culturas deportivas en las personas adultas, la femenina y la masculina, a traves del analisis de los niveles de practica (tipo de demanda), tipo de actividad practicada y sus caracteristicas (frecuencia semanal, gasto mensual, espacio de practica y modo de organizacion). La metodologia cuantitativa empleada ha consistido en la aplicacion de un cuestionario estructurado a una muestra aleatoria de las mujeres y varones mayores adultos entre 30 y 64 anos (n=340; 50.3% mujeres, 49.7% hombres) en la Comunidad de Madrid. Las conclusiones obtenidas revelan que un 45.3% de hombres y un 34.5% de mujeres practica deporte; ademas otro 15.5% de mujeres y 11.7% de hombres camina para hacer ejercicio. Aparecen diferencias de genero en las actividades practicadas (x2(10)=46.83; p.001; CC=.442), en el numero de horas de practica (t191=2.29; p.05; d=.33), en el gasto mensual (t148=3.16; p.001; d=.69) y en el modo de desplazamiento a la actividad (x2(7)=27.44; p0.001; CC=0.359) aunque la practica de actividades auto-organizadas es mayoritaria en ambos sexos (80.3% hombres, 63.7% mujeres), principalmente en solitario (62.7% hombres, 50.5% mujeres) y en espacios al aire libre (60.4% hombres, 46.6% mujeres).

Diferencias de género en los hábitos de actividad física de la población adulta en la Comunidad de Madrid Gender differences in the habits of physical activity of the adult population in the Community of Madrid

Abstract: La investigacion persigue contrastar la hipotesis de la existencia de dos diferentes culturas deportivas en las personas adultas, la femenina y la masculina, a traves del analisis de los niveles de practica (tipo de demanda), tipo de actividad practicada y sus caracteristicas (frecuencia semanal, gasto mensual, espacio de practica y modo de organizacion). La metodologia cuantitativa empleada ha consistido en la aplicacion de un cuestionario estructurado a una muestra aleatoria de las mujeres y varones mayores adultos entre 30 y 64 anos (n=340; 50.3% mujeres, 49.7% hombres) en la Comunidad de Madrid. Las conclusiones obtenidas revelan que un 45.3% de hombres y un 34.5% de mujeres practica deporte; ademas otro 15.5% de mujeres y 11.7% de hombres camina para hacer ejercicio. Aparecen diferencias de genero en las actividades practicadas (x2(10)=46.83; p<.001; CC=.442), en el numero de horas de practica (t191=2.29; p<.05; d=.33), en el gasto mensual (t148=3.16; p<.001; d=.69) y en el modo de desplazamiento a la actividad (x2(7)=27.44; p<0.001; CC=0.359) aunque la practica de actividades auto-organizadas es mayoritaria en ambos sexos (80.3% hombres, 63.7% mujeres), principalmente en solitario (62.7% hombres, 50.5% mujeres) y en espacios al aire libre (60.4% hombres, 46.6% mujeres). Palabras clave: habitos; actividad fisica; genero, adultos. R e s u m e n

Effect of processing parameters and void content on mechanical properties and NDI of thermoplastic composites

Abstract: Several consolidation cycles were performed to study the impact of processing parameters on void content, ultrasonic NDT and mechanical performance of CF/PEEK composites. A series of [+45/−45]4S laminates were manufactured by out-of-autoclave technologies including vacuum bag only, hot-press, and automatic lay-up with in-situ consolidation. A range of porosity between 0 and 19% of void content was assessed by varying the processing temperature from 340 to 500 °C and pressure from 0.25 to 1.5 MPa. Void content, shape and location were characterized by using C-scan, matrix digestion and 2D microscopy. Mechanical characterization including in-plane shear and interlaminar shear testing was performed. The results show a critical void content where properties start to decrease at a given drop-off rate. The results suggest that each processing technology should have its own quality control criteria. The proposed methodology is useful for engineering applications of thermoplastic composites and the creation of NDT acceptance criteria.

Advanced Thermoplastic Composite Manufacturing by In-Situ Consolidation: A Review

Abstract: This article provides an overview of the evolution of the in-situ consolidation (ISC) process over time. This evolution is intimately linked with the advancements in each of the steps of the ISC manufacturing process, is additive in nature, and is limited by the orthotropic nature of composite materials and the physicochemical behavior of the thermoplastic matrix. This review covers four key topics: (a) Thermal models—simulation tools are critical to understand a process with such large spatial gradients and fast changes. Heating systems once marked a turning point in the development of industrial ISC systems. Today, lasers are the most recent trend, and there are three key issues being studied: The absorption of energy of light by the material, the laser profile, and the laser focusing. Several approaches have been proposed for the distributed temperature measurements, given the strong temperature gradients. (b) Adhesion—this refers to two subsequent mechanisms. In the first place, the process of intimate contact is one by which two surfaces of thermoplastic pre-impregnated composite materials are brought into contact under pressure and temperature. This enables closure of the existing gaps between the two microscopic irregular surfaces. This process is then followed by the healing or diffusion of polymer molecules across the interface. (c) Crystallinity—mostly influenced by the cooling rate, and strongly affects the mechanical properties. (d) Degradation—this refers to the potential irreversible changes in the polymer structure caused by the high temperatures required for the process. Degradation can be avoided through adequate control of the process parameters. The end goal of the ISC manufacturing process is to achieve a high product quality with a high deposition rate through an industrial process competitive with the current manufacturing process for thermoset composites.

Defect Characteristics and Online Detection Techniques During Manufacturing of FRPs Using Automated Fiber Placement: A Review.

Abstract: Automated fiber placement (AFP) is an advanced manufacturing method for composites, which is especially suitable for large-scale composite components. However, some manufacturing defects inevitably appear in the AFP process, which can affect the mechanical properties of composites. This work aims to investigate the recent works on manufacturing defects and their online detection techniques during the AFP process. The main content focuses on the position defect in conventional and variable stiffness laminates, the relationship between the defects and the mechanical properties, defect control methods, the modeling method for a void defect, and online detection techniques. Following that, the contributions and limitations of the current studies are discussed. Finally, the prospects of future research concerning theoretical and practical engineering applications are pointed out.