Advanced composite material simulation

A computational methodology is presented for modeling the non-linear mechanical behavior of composite structures made of FRP (Fiber-Reinforced Polymers) laminates. The model is based on the appropriate combination of the constitutive models of compounding materials, considered to behave as isolated continua, together with additional “closure equations” that characterize the micro-mechanics of the composite from a morphological point of view. To this end, any appropriate constitutive model may be selected for each phase. Each component is modeled separately and the global response is obtained by assembling all contributions taking into account the interactions between components in a general phenomenological way. To model the behavior of a single uni-directional (UD) composite laminated, a Serial-Parallel continuum approach has been developed assuming that components behave as parallel materials in the fibers alignment direction and as serial materials in orthogonal directions. Taking into account the internal morphology of the composite material, it is devised a strategy for decoupling and coupling component phases. This methodology [Rastellini 2006], named "compounding of behavior", allows to take into consideration local non linear phenomenon in the compounding materials, like damage, plasticity, etc. in a coupled manner. It is based on the proper management of homogenous constitutive models, already available for each component. In this way, it is used all developments achieved in constitutive modeling for plain materials, what makes possible the transference of this technology to composites. A laminated theory complemented with the proposed UD model is employed to describe the mechanical behavior of multi-directional laminates. A specific solution strategy for the general non linear case is proposed. It provides quick local and global convergences, what makes the model suitable for large scale structures. The model brings answers on the non-linear behavior of composites, where classical micro-mechanics formulas are restricted to their linear elastic part. The methodology is validated through several numerical analyses and contrasted against experimental data and benchmark tests.Peer ReviewedPostprint (published version

Modelización numérica de la no-linealidad constitutiva de laminados compuestos

La respuesta mecánica de los materiales compuestos depende del comportamiento de los materiales componentes y de su micro‐estructura. Para mejorar y optimizar el diseño de piezas estructurales de materiales compuestos, la industria requiere herramientas informáticas que reproduzcan de manera apropiada el comportamiento de estos materiales incluso en el rango no lineal. Por tanto, es muy importante la investigación y desarrollo de modelos numéricos para compuestos  que tengan en cuenta la morfología o estructura del material de forma adecuada y eficiente, además de ser necesario contar con un entorno gráfico específico para este tipo de problemas que facilite la entrada de datos al código de cálculo y posteriormente permita visualizar los resultados deseados. El objetivo principal del presente trabajo es el desarrollo, formulación e implementación computacional, de un modelo numérico para el tratamiento de la no linealidad constitutiva de laminados reforzados con fibras, en el contexto de la mecánica de los medios continuos. Esta formulación plantea combinar (o componer) los comportamientos de materiales simples (homogéneos) con el objetivo de obtener la respuesta mecánica del material compuesto (heterogéneo). Para ello, propone una gestión adecuada de los modelos constitutivos (homogéneos), actualmente disponibles, de cada uno de los materiales componentes; aprovechándose de esta manera el gran desarrollo conseguido en el campo de la modelización constitutiva de materiales simples, y permitiendo la transferencia de toda esta tecnología al campo de los materiales compuestos. Teniendo en cuenta la estructura interna del material compuesto, se desarrolla una estrategia de desacoplamiento e interacción de estas fases; de una manera novedosa. Esta metodología, denominada “composición de comportamientos”, permite tener en cuenta muchos fenómenos locales de degradación que tienen lugar en las fases componentes, tales como plasticidad, daño, fatiga, envejecimiento, fluencia, etc., de una manera acoplada, lo cual también es novedoso en este tipo de enfoque. Las aplicaciones del presente trabajo se centran en los tres primeros fenómenos mencionados, dado que su combinación permite simular el comportamiento de una extensa variedad de materiales compuestos empleados en la industria. Se desarrolla el algoritmo de resolución del modelo propuesto que permite conseguir convergencia cuadrática, tanto local como global, de los problemas no‐ lineales al ser implementado como modelo constitutivo en un código de elementos finitos, proveyendo rapidez y precisión al análisis de estructuras de materiales compuestos en muchas aplicaciones industriales. La simulación del laminado se logra mediante la combinación del modelo propuesto con una teoría de laminado aplicada en cada punto de integración. Se emplean elementos 3D sólidos isoparamétricos para discretizar estructuras laminadas gruesas; mientras que para estudiar estructuras laminares de pequeño espesor, se desarrolla un elemento de lámina laminado en capas de material compuesto, sobre la base de un elemento de lámina más simple (Discrete Kirchoff Triangle). La validación del modelo muestra el cumplimiento de las ecuaciones de cierre (equilibrio de tensiones y compatibilidad de deformaciones entre componentes), tanto en la dirección de las fibras (comportamiento en paralelo) como en direcciones ortogonales (comportamiento en serie). Además, se ilustran diversas envolventes de fallo para lámina/laminados generadas con el modelo propuesto y se las compara con otros criterios de fallo global para compuestos y resultados experimentales disponibles en la literatura. La aplicabilidad del modelo se demuestra mediante simulaciones numéricas realizadas sobre geometrías de mayor complejidad para modelar la respuesta mecánica de piezas industriales. Los resultados numéricos contrastados con los experimentales indican la capacidad del modelo propuesto para describir el comportamiento no‐lineal de laminados reforzados con fibras en diferentes orientaciones sometidos a estados de carga multiaxial tanto estática como cíclica

Advanced composite material simulation

A computational methodology is presented for modelling the material non-linear mechanical behaviour of composite structures made of FRP (Fibre-Reinforced Polymers) laminates. The model is based on the appropriate combination of the constitutive models of component materials, considered to behave as isolated continua, together with additional ‘closure equations’ that characterize the micromechanics of the composite from a morphological point of view. To this end, any appropriate constitutive model may be selected for each phase. Each component is modelled separately and the global response is obtained by assembling all contributions taking into account the interactions between components in a general phenomenological way. To model the behaviour of a single unidirectional (UD) composite lamina, a Serial-Parallel continuum approach has been developed assuming that components behave as parallel materials in the fibres alignment direction and as serial materials in orthogonal directions. Taking into account the internal morphology of the composite material, it is devised a strategy for decoupling and coupling component phases. This methodology [Rastellini 2006], named “compounding of behaviours”, allows to take into consideration local degradation phenomena (in the constituents materials), like plasticity, etc. in a coupled manner. It is based on the proper management of homogenous constitutive models, already available for each component. In this way, it is used all developments achieved in constitutive modelling of plain materials, what makes possible the transference of this technology to composites. A lamination theory complemented with the proposed UD model is employed to describe the mechanical behaviour of multidirectional laminates. A specific solution strategy for the general non linear case is proposed. It provides quick local and global convergences, what makes the model suitable for large scale structures. The model brings answers on the non-linear behaviour of composites, where classical micro-mechanics formulas are restricted to their linear elastic part. The methodology is validated through several numerical analyses and contrasted against experimental data and benchmark tests.Peer ReviewedPostprint (published version

Advanced composite material simulation

A computational methodology is presented for modeling the non-linear mechanical behavior of composite structures made of FRP (Fiber-Reinforced Polymers) laminates. The model is based on the appropriate combination of the constitutive models of compounding materials, considered to behave as isolated continua, together with additional “closure equations” that characterize the micro-mechanics of the composite from a morphological point of view. To this end, any appropriate constitutive model may be selected for each phase. Each component is modeled separately and the global response is obtained by assembling all contributions taking into account the interactions between components in a general phenomenological way. To model the behavior of a single uni-directional (UD) composite laminated, a Serial-Parallel continuum approach has been developed assuming that components behave as parallel materials in the fibers alignment direction and as serial materials in orthogonal directions. Taking into account the internal morphology of the composite material, it is devised a strategy for decoupling and coupling component phases. This methodology [Rastellini 2006], named "compounding of behavior", allows to take into consideration local non linear phenomenon in the compounding materials, like damage, plasticity, etc. in a coupled manner. It is based on the proper management of homogenous constitutive models, already available for each component. In this way, it is used all developments achieved in constitutive modeling for plain materials, what makes possible the transference of this technology to composites. A laminated theory complemented with the proposed UD model is employed to describe the mechanical behavior of multi-directional laminates. A specific solution strategy for the general non linear case is proposed. It provides quick local and global convergences, what makes the model suitable for large scale structures. The model brings answers on the non-linear behavior of composites, where classical micro-mechanics formulas are restricted to their linear elastic part. The methodology is validated through several numerical analyses and contrasted against experimental data and benchmark tests.Peer Reviewe

Advanced composite material simulation

A computational methodology is presented for modelling the material non-linear mechanical behaviour of composite structures made of FRP (Fibre-Reinforced Polymers) laminates. The model is based on the appropriate combination of the constitutive models of component materials, considered to behave as isolated continua, together with additional ‘closure equations’ that characterize the micromechanics of the composite from a morphological point of view. To this end, any appropriate constitutive model may be selected for each phase. Each component is modelled separately and the global response is obtained by assembling all contributions taking into account the interactions between components in a general phenomenological way. To model the behaviour of a single unidirectional (UD) composite lamina, a Serial-Parallel continuum approach has been developed assuming that components behave as parallel materials in the fibres alignment direction and as serial materials in orthogonal directions. Taking into account the internal morphology of the composite material, it is devised a strategy for decoupling and coupling component phases. This methodology [Rastellini 2006], named “compounding of behaviours”, allows to take into consideration local degradation phenomena (in the constituents materials), like plasticity, etc. in a coupled manner. It is based on the proper management of homogenous constitutive models, already available for each component. In this way, it is used all developments achieved in constitutive modelling of plain materials, what makes possible the transference of this technology to composites. A lamination theory complemented with the proposed UD model is employed to describe the mechanical behaviour of multidirectional laminates. A specific solution strategy for the general non linear case is proposed. It provides quick local and global convergences, what makes the model suitable for large scale structures. The model brings answers on the non-linear behaviour of composites, where classical micro-mechanics formulas are restricted to their linear elastic part. The methodology is validated through several numerical analyses and contrasted against experimental data and benchmark tests.Peer Reviewe