Search results for " composite materials"

Longitudinal Flexure as a Method for Determining the Flexural Strength of Composite Materials

2004

A method is presented for determining the flexural strength of composites from tests on pinned specimens in axial compression. This scheme is close to the so-called Euler buckling model, but the load is applied eccentrically, and the bar is bent practically from the beginning of loading. An analytical model is proposed for calculating the flexural stress in longitudinal flexure of a thin bar in the case of large displacements. The problem is solved in elliptic integrals of the first and second kinds. The analytical model shows an excellent agreement with experiments. The results obtained are compared with experimental tension data. A device is also designed for testing composite bars in lon…

Quantifiable analysis of the failure of advanced carbon fibre composite structures leading to improved safety factors

2022

Abstract The increasing use of advanced composite materials means that they must now be considered as major materials for a wide variety of structures some of which will be in service for decades. There is therefore an important need to be able to quantify damage accumulation leading to failure in these materials particularly as they are often used in extreme situations for which failure must be avoided. This review shows how damage accumulation in many major composite structures is dominated by fibre failure but that the viscoelastic nature of the matrix induces time effects including delayed failure. It is shown that damage accumulation can be quantitatively modelled using a multi-scale a…

Manufacture of marine composite sandwich structures

2016

Abstract The aim of this chapter is to present the main processes of manufacture of composite sandwich structures used in marine applications. In the introduction, sandwich structure classification and properties and advantages/disadvantages in their uses are presented. In the second and third section, the main used technologies to made sandwich are, respectively, described and compared. Then, the goodness of these techniques is evidenced with the discussion of some experimental results obtained by the authors in their studies. The last section concludes with a thorough list of the future trends.

VIRTUAL ELEMENT METHOD FOR COMPUTATIONAL HOMOGENIZATIONS OF UNIDIRECTIONAL FIBER-REINFORCED COMPOSITE MATERIALS

2019

The Virtual Element Method (VEM) is a generalization of the Finite Element Method (FEM) for the treatment of general polygonal/polyhedral mesh elements. Despite its recent introduction, VEM has been applied to several problems in structural mechanics. Due to such capability of dealing with mesh elements of general shape and of naturally addressing the presence of hanging nodes, the VEM ensures a noticeable simplification in the data preparation stage of the analysis, allowing implementing a mesh generation process over complex multi-domain geometries in a fully automated way. Moreover, for the lowest order VEM used in this contribution,no numerical integration is required to compute the sys…

Ionizing radiation induced curing of epoxy resin for advanced composites matrices

2005

Abstract The radiation curing of an epoxy monomer in the presence of an iodonium salt, as photo initiator, is studied. Systems with different concentrations of photo initiators have been polymerized via both gamma rays and e-beam, at various dose rates. The aim of this work is to investigate how the photo initiator concentration and the irradiation dose rate affect the temperature of the systems during curing and how the different thermal histories influence the dynamic mechanical thermal properties of the obtained materials.

The influence of the processing temperature on gamma curing of epoxy resins for the production of advanced composites

2007

Abstract Gamma radiation curing of an epoxy monomer, in the presence of an iodonium salt, as initiator, is studied. Systems have been polymerized at the same irradiation dose and dose rate and at different processing temperatures. The experimental results show that all the irradiated materials exhibit a latent reactivity, undergoing toward an increase of crosslinking density if they are thermally cured after irradiation. The results indicate that the processing temperature affects both the crosslinking density after irradiation and the sensibility to the post-irradiation thermal treatment.

Adhesive inter-laminar and cohesive inner-layer damage mechanisms for composite materials

2009

Virtual Element based formulations for computational materials micro-mechanics and homogenization

2021

In this thesis, a computational framework for microstructural modelling of transverse behaviour of heterogeneous materials is presented. The context of this research is part of the broad and active field of Computational Micromechanics, which has emerged as an effective tool both to understand the influence of complex microstructure on the macro-mechanical response of engineering materials and to tailor-design innovative materials for specific applications through a proper modification of their microstructure. While the classical continuum approximation does not account for microstructural details within the material, computational micromechanics allows detailed modelling of a heterogeneous…

Analisi quantitativa dell'effetto termoelastico in materiali compositi CFRP

2008

ELEMENTO D’INTERFACCIA PER LA SIMULAZIONE DI PROCESSI DI DANNEGGIAMENTO IN MODO MISTO I/II NEI MATERIALI COMPOSITI E NELLE GIUNZIONI ADESIVE

2018

E’ stato sviluppato un elemento coesivo in grado di connettere e simulare la crescita delle cricche tra sottodomini di elementi finiti modellati in modo indipendente con mesh incompatibili. L'approccio si basa su funzioni di penalità e presenta numerosi vantaggi rispetto alle tecniche FEM convenzionali nelle simulazioni di delaminazione. Il più importante è la possibilità di rilasciare una porzione dell'interfaccia più piccola della lunghezza degli elementi finiti locali. Pertanto la delaminazione non avanza solamente rilasciando i nodi del modello FEM, una limitazione comune a molti metodi trovati in letteratura. È stato anche sviluppato un nuovo approccio per modellare la crescita delle c…