is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in: https://sam.ensam.eu Handle IDa b s t r a c tDrilling of composite material structure is a widely used process in aeronautical assembly due to its best manufacturing value (ratio quality/cost). However, delamination which can be generated at the hole exit is still a problem and is directly related to the drill axial force, the composite material mechanical characteristics and the load distribution along the cutting and chisel edges. This paper analyzes the distribution of the load along the drill edges and points out a triangular distribution associated to an additional load located at the centre of the drill. This additional load depends strongly on the feed rate. An orthotropic analytical model is then proposed in order to determine the delamination critical thrust during drilling for different combined loadings. This new model is compared with the existing ones in the literature and with experimental results. This analysis highlights that delamination occurs in a mixed mode and not in mode I only. The use of the B-K criterion for the determination of the equivalent critical energy release rate G C and a cutting edge combined loading (triangular distribution associated to an additional load) allow a close correlation between experimental measurements and the prediction of this new model.

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. AbstractThe indentation response of glasses can be classified under three headings: normal, anomalous and intermediate, depending on the deformation mechanism and the cracking response. Silica glass, as a typical anomalous glass, deforms primarily by densification and has a strong tendency to form cone cracks that can accompany median, radial and lateral cracks when indented with a Vickers tip. This is due to its propensity to deform elastically by resisting plastic flow. Several investigations of this anomalous behavior can be found in the literature. The present paper serves to corroborate these results numerically using the discrete element method. A new pressuredensification model is developed in this work that allows for a quantitative estimate of the densification under very high pressure. This model is applied to simulate the Vickers indentation response of silica glass under various indentation forces using the discrete element method first, and then a discrete-continuum coupling method with large simulation domains to suppress the side effects and reduce the computational time. This coupling involves the discrete element method (DEM) and the constrained natural element method (CNEM). The numerical results obtained in this work compare favorably with past experimental results.

International audienceIn this article, the Discrete Element Method (DEM) is taking advantage for the damage modeling of a composite material. At this stage of work, a Representative Elementary Volume (REV) of an unidirectional composite material modeled in 3D is considered to prove the relevance of the approach. The interest to introduce the Discrete Elements (DE) on the scale of constituents (fiber and matrix) is to be able to report local mechanisms of degradation such as the matrix micro-fissuring, the fiber/matrix debonding and the break of fiber, appropriate to this type of material. The short-term objective is to use this DEM modeling to treat locally the damages induced by an impact loading associated with a conventional Finite Element modeling beyond the damaged zone. First, the geometrical modelings of the fiber and the matrix are presented. The phase of calibration of the DE model intrinsic parameters governing the fiber and matrix behavior and the fiber/matrix interface is afterward retailed. At this stage, each constituent is assumed to be brittle elastic. Then, simulations of longitudinal and transversal tensions but also of in plane and out of plane shearing are performed on the REV using DEM. The results are discussed and compared with those known for the literature. The capacity of the present DEM to capture the crack paths is particularly highlighted

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. a b s t r a c tThe coupling between two dissimilar numerical methods presents a major challenge, especially in case of discrete-continuum coupling. The Arlequin approach provides a flexible framework and presents several advantages in comparison to alternative approaches. Many studies have analyzed, in statics, the ingredients of this approach in 1D configurations under several particular conditions. The present study extends the Arlequin parameter studies to incorporate a dynamic behavior using 3D models. Based on these studies, a new 3D coupling method adapted for dynamic simulations is developed. This method couples two 3D codes: DEM-based code and CNEM-based code. The 3D coupling method was applied to several reference dynamics tests. Good results are obtained using this method, compared with the analytical and numerical results of both DEM and CNEM.

This paper presents a 3D simulation of damages and cracks growth in composite material using Discrete Element Method (DEM). Fiber/matrix debonding and ply to ply delamination, cracks matrix, rupture of fibers are addressed. Matrix and fiber are supposed to be brittle materials and follow a linear fracture model. Cohesive contact laws are implemented to model interfaces behavior for both debonding (fiber/ matrix) and delamination (ply/ply). Piecewise linear elastic laws usually used in cohesive zone models are retained in this work. A Double Cantiliver Beam (DCB) test is first experimented using the present DEM with Cohesive Contact Models (CCM). Then, based on De Borst's works [1], a single fiber composite under transverse traction is modeled to study debonding and matrix cracks propagations depending on the matrix and the fiber/matrix interface strengths ratio. A bi-disperse medium for matrix and fiber is specifically elaborated to reduce the discrete elements number. The analysis is extended to a so-called multi-fibers composite specimen, also called Statistical Elementary Volume (SEV), made of several fibers embedded in the matrix. Finally, the results are compared with DeBorst's works and qualitatively discussed.

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This paper deals with a new triangular finite element to analyze the behaviour of multilayered shells. This element is based on a refined kinematical model and uses both conforming finite element method and higher-order approximations. Including a nonlinear distribution with respect to the normal co-ordinate for the transverse shear stresses and continuity requirements between layers for both transverse shear stresses and displacements, this model does not require any shear correction factors. Moreover, it allows to satisfy the boundary conditions at the top and bottom surfaces of the shell. Various strain expressions available for shells are discussed. Although the program is able to calculate arbitrary shell shapes, present shell element performances are evaluated here in comparison with available analytical tests issued from literature. The present finite element shown very good responses on the classical shell test: pinched cylinder, pinched hemispherical shell, Scordelis-Lo roof. Finally, results in linear static, free vibrations and transient dynamic response for multilayered shells show the efficiency of this new shell finite element.

This work deals with the problem of characterising the elastic properties of a composite material at both mesoscopic (ply-level) and microscopic (constitutive phases-level) scales. This goal is attained by means of an adequate multi-scale identification strategy (MSIS) which aims at identifying the constitutive properties, at each relevant scale, by exploiting the information restrained in the macroscopic dynamic response of the composite. In this background, the multi-scale identification problem is split into two interdependent sub-problems which are stated, at both levels, as constrained minimisation problems. At the first level the goal is the characterisation of the lamina properties by minimising the distance between the numerical and the reference harmonic responses of the composite. The second level problem aims at identifying the elastic properties of both fibre and matrix by minimising the distance between the effective elastic properties evaluated through a homogenisation process and those provided by the first-level inverse problem. The MSIS is based on a special global hybrid optimisation tool and on the strain energy homogenisation method of periodic media. Its effectiveness is proven through a meaningful benchmark. 12 ν f 23 G f 12 [MPa] E m [MPa] ν m 276000.0 17300.0 0.250 0.428 11240.0 4140.0 0.350