Search results for "Delamination"

The effect of through-thickness compressive stress on mode II interlaminar fracture toughness

2017

Abstract The effect of through-thickness compressive stress on mode II interlaminar fracture toughness is investigated experimentally and replicated numerically. The modified Transverse Crack Tensile specimen recently proposed by the authors is used, together with an experimental device designed to apply a constant transverse compressive stress on the surface of the specimen. Experiments are conducted using IM7/8552 specimens for different compressive stresses, ranging from 0 to 100 MPa, covering all the practical applications commonly encountered in the aeronautical industry (e.g., tightened filled holes or bolted joints). It is shown that mode II interlaminar fracture toughness increases …

Bending-Induced Delamination of van der Waals Solids

2013

Although sheets of layered van der Waals solids offer great opportunities to custom-design nanomaterial properties, their weak interlayer adhesion challenges structural stability against mechanical deformation. Here, bending-induced delamination of multilayer sheets is investigated by molecular dynamics simulations, using graphene as an archetypal van der Waals solid. Simulations show that delamination of a graphene sheet occurs when its radius of curvature decreases roughly below $R_c=5.3\text{nm}\times (\text{number of layers})^{3/2}$ and that, as a rule, one-third of the layers get delaminated. These clear results are explained by a general and transparent model, a useful future referenc…

Numerical analysis of composite plates with multiple delaminations subjected to uniaxial buckling load

2006

Abstract In this paper the buckling and post-buckling behaviour of unidirectional and cross-ply composite laminated plates with multiple delaminations has been studied. Finite elements analyses have been performed, using a linear buckling model, based on the solution of the eigenvalues problem, and a non-linear one, based on an incremental-iterative method. With non-linear method large displacements have been taken into account and also contact constraints between sublaminates have been added to avoid their interpenetration. It has been found that both delamination length and position and stacking sequence of the plies influence the critical load of the plate; furthermore, linear and non-li…

Incremental Delamination Processes under Cyclic Loading

2012

Numerical simulation of fatigue-driven delamination using interface elements

2005

This paper presents a computational technique for the prediction of fatigue-driven delamination growth in composite materials. The interface element, which has been extensively applied to predict delamination growth due to static loading, has been modified to incorporate the effects of cyclic loading. Using a damage mechanics formulation, the constitutive law for the interface element has been extended by incorporating a modified version of a continuum fatigue damage model. The paper presents details of the fatigue degradation strategy and examples of the predicted fatigue delamination growth in mode I, mode II and mixed mode I/II are presented to demonstrate that the numerical model mimics…

Effet de l'orientation des fibres des plis adjacents sur la résistance au délaminage en mode I pur = Effect of the fibre's orientation of adjacent pl…

2009

National audience; Ce travail concerne l'étude de l'effet de l'orientation des fibres des plis adjacents à la fissure dans une éprouvette DCB (Double Cantilever Beam) sur la résistance au délaminage en mode I pur. Afin d'isoler l'influence de l'orientation l'étude porte sur des stratifiés particuliers ayant tous les mêmes matrices de comportement global A B D. Les résultats expérimentaux montrent une grande variation de résistance au délaminage GIC et des courbes R selon l'orientation des plis situés de part et d'autre du plan de fissure. Une modélisation par éléments finis permet de mettre en évidence l'importance de l'état de contraintes locales et donc de l'endommagement au voisinage du …

A Strain Sensing Structural Health Monitoring System for Delaminated Composite Structures

2012

Structural Health Monitoring (SHM) for composite materials is becoming a primary task due to their extended use in safety critical applications. Different methods, based on the use of piezoelectric transducers as well as of fiber optics, has been successfully proposed to detect and monitor damage in composite structural components with particular attention focused on delamination cracks.In the present paper a Structural Health Monitoring model, based on the use of piezoelectric sensors, already proposed by the authors for isotropic damaged components, is extended to delaminated composite structures. The dynamic behavior of the host damaged structure and the bonded piezoelectric sensors is m…

A Cohesive-frictional interface model subjected to mixed complex loading paths

2017

The paper presents a cohesive-frictional interface model based on surface damage mechanics. The proposed model is developed under the assumption that the fracture energies in mode I and in mode II are different values, as shown by several experimental evidences. At difference with the most spread available interface models, only one isotropic interface internalvariable is adopted for the constitutive model. The interface constitutive model is developed in a Thermodynamic consistent framework with an Helmholtz free energy potential and the fulfillment of the thermodynamic principles is obtained enforcing the Clausius-Duhem inequality. The damage/friction activation functions and dissipative …

Numerical analysis of delamination in through-thickness reinforced composite laminates

2009

Composite laminates show a high vulnerability to out-of-plane actions, responsible for localized damage between two adjacent laminae, i.e. delamination phenomenon. A recent technological solution to improve the strength of the composite laminates in the thickness direction consists in inserting through-thickness reinforcement. In this paper, the composite delamination is analyzed in the context of non-linear fracture mechanics by an original two-phase interface model able to describe the anisotropic elastic and post-elastic mechanical response given by the presence of the reinforcement fibres. The two phases (adhesive joint or matrix of the composite and the reinforcement) are characterized…

A DIC-based study of flexural behaviour of roving/mat/roving pultruded composites

2015

Abstract This paper reports a study of the flexural behaviour and resultant failure modes in E-glass/polyester pultruded composites. The digital image correlation (DIC) method is used to estimate the effect of fibre orientation on failure behaviour in thick beams, taking into account the presence of continuous filament mat layer (CFM) in the stacking sequence. In particular, the tests were carried out for specimens with off-axis angle of 0°, 7.5°, 15°, 30°, 45° and 90°. The crack initiation and the failure mechanisms depend on the mutual interaction between the stiffness properties of different areas in the stacking sequence. An influence index (I) was introduced to evaluate the magnitude o…