Search results for "lamination"

A delamination test for structural wood adhesives used in thick joints

2001

A test method was developed for the measurement of delamination of structural wood adhesives applied in thick joints. Large differences were observed within a range of 8 commercial epoxy-based products.

Cohesive Model for the Simulation of Crack Initiation and Propagation in Mixed-Mode I/II in Composite Materials

2019

A cohesive element able to connect and simulate crack growth between independently modeled finite element subdomains with non-matching meshes is proposed and validated. The approach is based on penalty constraints and has several advantages over conventional FE techniques in disconnecting two regions of a model during crack growth. The most important is the ability to release portion of the interface that are smaller than the local finite element length. Thus, the growth of delamination is not limited to advancing by releasing nodes of the FE model, which is a limitation common to the methods found in the literature. Furthermore, it is possible to vary the penalty parameter within the cohes…

BE contact analysis of delamination cracks actively repaired trhough piezoelectric active patches

2009

BE analysis of delaminated Composite Structures repaired with Piezoelectric Active patches

2009

The main target of the present paper is the analysis of the fracture mechanics behavior of delaminated composite structures actively repaired through piezoelectric patches. The aim at issue has been achieved by using a boundary element code implemented to study piezoelectric solids, including, as limiting case, the applicability to linear elastic anisotropic materials. The assembled structures, made up of the damaged composite components and the piezoelectric patches, have been modelled through the multidomain technique. To take into account for the adhesive layer among the host structure and the active patch, an interface spring-model has been also implemented. The multidomain technique co…

Application of the 3-D boundary element method to delaminated composite structures

2013

A three-dimensional boundary element model for anisotropic solids is presented to study the fracture mechanics behavior of delaminated composite structures. The multi-domain technique is implemented to model the layered configurations and the cracks occurring at bi-material interface. The Modified Crack Closure Integral technique is implemented to characterize the fracture mechanics behavior of delaminations in terms of the total energy release rate and mode mix phase angles. Validating analyses, performed on different delaminated configurations, have shown the effectiveness of the proposed approach. Moreover, some original results are presented to investigate the effects of the stacking se…

3D boundary element analysis of delamination crack using the Modified Crack Closure Integral

2012

Structural Health Monitoring of delaminated composite structures by the Boundary Element method

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, strain memory alloys as well as of fibre 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 piez…

Tensile behaviour of anti-symmetric CFRP composite

2011

Abstract This paper addresses the response of a 17-ply anti-symmetric carbon/epoxy composite subjected to uniaxial tensile loading. Hashin ply damage model is adopted to describe the damage behaviour of the plies, whereas damage initiation and progression of the interfaces are characterised by mixed-mode cohesive damage model. Force-displacement curves obtained numerically and experimentally show good agreement. Results show that all laminae and interfaces experience the damage except laminae with 0o fibre. In addition, damage is concentrated at the tab and central regions of the tensile specimen. Edge delamination is observed in all interfaces.

Evolution Characteristics of Delamination Damage in CFRP Composites Under Transverse Loading

2012

The initiation and subsequent progression of delamination in CFRP composite laminates is examined using finite element method. A 12-ply CFRP composite, with a total thickness of 2.4 mm and anti-symmetric ply sequence is simulated under three-point bend test setup. Each unidirectional composite lamina is treated as an equivalent elastic and orthotropic panel. Interface behavior is defined using cohesive damage model. Complementary three-point bend test on the specimen is performed at crosshead speed of 2 mm/min. The measured load–deflection response at mid-span location compares well with predicted values. Interface delamination accounts for up to 46.7% reduction in flexural stiffness from t…

Numerical and Experimental Analysis of the Frictional Effects on 4ENF Delamination Tests Performed on Unidirectional CFRP

2015

Abstract Progressive delamination in composite materials under static or fatigue loading condition are, in many structures, one of the predominant cause of failure. In the paper, an accurate study of quasi-static delamination growth under mode II loading condition is conducted. Several experimental tests are performed on composite laminates consisting of unidirectional carbon/epoxy layers. Four-point end-notched flexure (4ENF) test is employed in order to characterize the mode II interlaminar fracture toughness. The R-curve is obtained by means of optical and numerical determination of crack tip position. The energy release rate and the crack length are calculated through experimental deter…