Publication: Análisis y modelización del comportamiento de placas de tejido carbono/epoxi ante impacto
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2021-06
Defense date
2021-09-24
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Abstract
La eficiencia energética representa un factor determinante a la hora de cumplir
los objetivos económicos y medioambientales marcados por los distintos sectores
industriales. En la industria del transporte, especialmente en la aeronáutica, el
cumplimiento de estos objetivos pasa por el desarrollo de estructuras optimizadas
en términos de peso y resistencia. En este aspecto, el uso de materiales compuestos
para el diseño de elementos estructurales ha demostrado ser una gran solución y
reto de diseño.
Los laminados de material compuesto (comúnmente empleados en la industria aeroespacial)
poseen unas excelentes propiedades mecánicas en el plano del laminado
pero una baja resistencia cuando son sometidos a impactos fuera del mismo. Experimentalmente,
se ha demostrado que impactos a baja velocidad de masas elevadas
pueden reducir de manera drástica las propiedades de estos laminados. Este factor
hace necesario el estudio del comportamiento y la resistencia de los laminados de
material compuesto sometidos a este tipo de impactos, teniendo en cuenta algunos
parámetros como el espesor o la secuencia de apilamiento de las láminas.
La presente tesis doctoral se centra en el estudio de impactos a baja velocidad
sobre laminados de tejido de obra de carbono con matriz epoxi. El estudio se ha
llevado a cabo analizando los daños provocados por este tipo de impactos sobre
distintas probetas de material compuesto, variando la energía de impacto y modificando el espesor y la secuencia de apilamiento de los laminados. Dentro de
este estudio, se ha profundizado en el efecto que provoca apilar de forma contigua
varias laminas con una misma orientación (ply clustering). Para llevar a cabo el
estudio se ha seguido una metodología combinada experimental y numérica.
Experimentalmente las probetas de material compuesto han sido sometidas a impactos
de baja velocidad empleando un torre de caída, capaz de proporcionar la
curva fuerza-tiempo y la velocidad del percutor en cada ensayo. Todos los ensayos
han sido grabados con dos cámaras de alta velocidad proporcionando la información necesaria para analizar el comportamiento de cada laminado durante el
proceso de impacto. Para completar el análisis, se ha empleado un sistema tridimensional
de correlación digital de imagen (3D DIC) permitiendo así evaluar el
campo de desplazamientos en tres dimensiones. Una vez impactadas, las probetas
han sido sometidas a una inspección por ultrasonidos (C-Scan) para analizar la
magnitud de los daños internos.
Numéricamente, se ha desarrollado una metodología para reproducir el comportamiento
de los laminados de tejido de fibra de carbono y matriz epoxi sometidos
a impactos de baja velocidad. Esta metodología ha sido validada comparando los
resultados numéricos y experimentales. Las simulaciones numéricas han sido realizadas
empleando el software comercial de elementos finitos Abaqus/Explicit v6.14.
El comportamiento del material compuesto ha sido implementado empleando un
modelo tridimensional de daño continuo capaz de reproducir los distintos mecanismos
de fallo intralaminares e interlaminares típicos de los materiales compuestos.
La metodología desarrollada ha permitido analizar el comportamiento de los laminados
de tejido de fibra de carbono y matriz epoxi sometidos a impactos de baja
velocidad. Se ha podido comprender la relación entre los distintos daños provocados
por cada impacto con los parámetros del laminado (espesor y secuencia de
apilamiento). Además, la validación numérica ha permitido constatar la capacidad
predictiva del modelo de material desarrollado. En conjunto, el trabajo realizado
ha permitido cuantificar y comprender la resistencia de los laminados de fibra de
carbono y matriz epoxi ante impactos de baja velocidad fuera del plano.
Energy eficiency represents a determining factor when it comes to meeting the economic and environmental objectives set by the different industrial sectors. In the transport industry, especially in aeronautics, the fulfillment of these objectives requires the development of optimized structures in terms of weight and resistance. In this regard, the use of composite materials for the design of structural elements has proven to be a great solution and design challenge. Composite laminates (commonly used in the aerospace industry) have excellent mechanical properties in the plane of the laminate but low resistance when subjected to out of plane impacts. Experimentally, it has been shown that low velocity impacts from high masses can drastically reduce the properties of these laminates. This factor makes it necessary to study the behavior and resistance of composite material laminates subjected to this type of impact, considering some parameters such as the plate thickness or the stacking sequence. In the present PhD Theis, it has been analyzed the behavior of carbon/epoxy laminates subjected to low velocity impacts. The study has been carried out by analyzing the damage caused by this type of impacts on different composite plates, varying the impact energy and modifying the thickness and stacking sequence of the laminates. Within this study, the effect of stacking several plies with the same orientation (ply clustering) has been studied. To fulfill this objective, a combined experimental and numerical methodology has been followed. Experimentally, the composite plates have been subjected to low velocity impacts using a drop tower, capable of providing the force-time curves and theimpactor velocity in each test. All the tests have been recorded with two high-speed cameras providing the necessary information to analyze the behavior of each laminate during the impact process. To complete the analysis, a three-dimensional digital image correlation system (3D DIC) was used to analyze the three dimensional displacement of the plates. Once impacted, the specimens have been subjected to an ultrasound inspection (C-Scan) to analyze the internal damages. A numerical methodology has been developed to reproduce the behavior of carbon/ epoxy fabric laminates subjected to low velocity impacts. This methodology has been validated by comparing the numerical and experimental results. The numerical simulations have been carried out using the commercial finite element software Abaqus / Explicit v6.14. The behavior of the composite material has been implemented using a three-dimensional model of continuous damage capable of reproducing the different intralaminar and interlaminar failure mechanisms typical of composite plates. The methodology developed has made it possible to analyze the behavior of carbon/ epoxy fabric laminates subjected to low velocity impacts. It has been possible to understand the relationship between the different damages caused by each impact with the laminate parameters (thickness and stacking sequence). In addition, the numerical validation has allowed to verify the predictive capacity of the developed material model. Together, the work carried out has made it possible to quantify and understand the resistance of carbon/epoxy fabric laminates subjected to low velocity impacts.
Energy eficiency represents a determining factor when it comes to meeting the economic and environmental objectives set by the different industrial sectors. In the transport industry, especially in aeronautics, the fulfillment of these objectives requires the development of optimized structures in terms of weight and resistance. In this regard, the use of composite materials for the design of structural elements has proven to be a great solution and design challenge. Composite laminates (commonly used in the aerospace industry) have excellent mechanical properties in the plane of the laminate but low resistance when subjected to out of plane impacts. Experimentally, it has been shown that low velocity impacts from high masses can drastically reduce the properties of these laminates. This factor makes it necessary to study the behavior and resistance of composite material laminates subjected to this type of impact, considering some parameters such as the plate thickness or the stacking sequence. In the present PhD Theis, it has been analyzed the behavior of carbon/epoxy laminates subjected to low velocity impacts. The study has been carried out by analyzing the damage caused by this type of impacts on different composite plates, varying the impact energy and modifying the thickness and stacking sequence of the laminates. Within this study, the effect of stacking several plies with the same orientation (ply clustering) has been studied. To fulfill this objective, a combined experimental and numerical methodology has been followed. Experimentally, the composite plates have been subjected to low velocity impacts using a drop tower, capable of providing the force-time curves and theimpactor velocity in each test. All the tests have been recorded with two high-speed cameras providing the necessary information to analyze the behavior of each laminate during the impact process. To complete the analysis, a three-dimensional digital image correlation system (3D DIC) was used to analyze the three dimensional displacement of the plates. Once impacted, the specimens have been subjected to an ultrasound inspection (C-Scan) to analyze the internal damages. A numerical methodology has been developed to reproduce the behavior of carbon/ epoxy fabric laminates subjected to low velocity impacts. This methodology has been validated by comparing the numerical and experimental results. The numerical simulations have been carried out using the commercial finite element software Abaqus / Explicit v6.14. The behavior of the composite material has been implemented using a three-dimensional model of continuous damage capable of reproducing the different intralaminar and interlaminar failure mechanisms typical of composite plates. The methodology developed has made it possible to analyze the behavior of carbon/ epoxy fabric laminates subjected to low velocity impacts. It has been possible to understand the relationship between the different damages caused by each impact with the laminate parameters (thickness and stacking sequence). In addition, the numerical validation has allowed to verify the predictive capacity of the developed material model. Together, the work carried out has made it possible to quantify and understand the resistance of carbon/epoxy fabric laminates subjected to low velocity impacts.
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Keywords
Epoxy, Laminados carbono/epoxi, Materiales compuestos con refuerzo de fibra de carbono, Resistencia de materiales, Ensayo de impacto, Resistencia frente a impacto, ABAQUS/Explicit, Industria aeroespacial