Constitutive relation and stiffness degradation of cracked anisotropic composite laminates(II) —determination of resolved stiffness and investigation of stiffness degradation for cracked laminates

A new approach for the nondestructive determination of the elastic properties of composite laminates is presented. The approach represents an improvement of a recently published experimental methodology based on the Impulse Excitation Technique, which allows nondestructively assessing local elastic properties of composite laminates by isolating a region of interest through a proper clamping system. Different measures of the first resonant frequency are obtained by rotating the clamping system with respect to the material orientation. Here, in order to increase the robustness of the inverse problem, which determines the elastic properties from the measured resonant frequencies, information related to the modal shape is retained by considering the effect of an additional concentrated mass on the first resonant frequency. According to the modal shape and the position of the mass, different values of the first resonant frequency are obtained. Here, two positions of the additional mass, i.e., two values of the resonant frequency in addition to the unloaded frequency value, are considered for each material orientation. A Rayleigh–Ritz formulation based on higher order theory is adopted to compute the first resonant frequency of the clamped plate with concentrated mass. The elastic properties are finally determined through an optimization problem that minimizes the discrepancy on the frequency reference values. The proposed approach is validated on several materials taken from the literature. Finally, advantages and possible limitations are discussed.

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The determination of Mode III fracture toughness in thick composite laminates

Composites Science and Technology ◽

10.1016/0266-3538(96)00009-7 ◽

1996 ◽

Vol 56 (4) ◽

pp. 489-499 ◽

Cited By ~ 35

Author(s):

W.C. Liao ◽

C.T. Sun

Keyword(s):

Fracture Toughness ◽

Composite Laminates ◽

Mode Iii

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Determination of the Residual Stresses in Composite Laminate Using the Compliance Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.490-491.533 ◽

2005 ◽

Vol 490-491 ◽

pp. 533-538 ◽

Cited By ~ 1

Author(s):

Guillaume Montay ◽

Olivier Sicot ◽

X.L. Gong ◽

Abel Cherouat ◽

Jian Lu

Keyword(s):

Experimental Data ◽

Residual Stresses ◽

Composite Laminates ◽

Composite Laminate ◽

Constant Width ◽

Strain Gages ◽

New Methods ◽

Structure Surface ◽

Finite Elements Simulation

Residual stresses play an important role on the mechanical behavior of composite laminate. The development of new methods to determine the residual stresses gradient within the laminates is necessary. This article presents the adaptation of the compliance method in the case of composite laminates carbon/epoxy [02/902]s. The incremental drilling of a constant width groove allows for each increment to measure the strains (using strain gages) and displacements (using an optical device) of particularly points of the structure surface. These experimental data are compared with results given by a finite elements simulation. This comparison allows to raise the residual stresses in the composite laminate.

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Prediction of stiffness degradation in hygrothermal aged [θm/90n]S composite laminates with transverse cracking

Journal of Materials Processing Technology ◽

10.1016/j.jmatprotec.2007.08.002 ◽

2008 ◽

Vol 199 (1-3) ◽

pp. 199-205 ◽

Cited By ~ 14

Author(s):

E.A. Adda-bedia ◽

M. Bouazza ◽

A. Tounsi ◽

A. Benzair ◽

M. Maachou

Keyword(s):

Composite Laminates ◽

Stiffness Degradation ◽

Transverse Cracking

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NUMERICAL PREDICTION OF STIFFNESS DEGRADATION OF THIN-PLY CFRP LAMINATES UNDER FATIGUE LOADING

10.12783/asc36/35892 ◽

2021 ◽

Author(s):

RYOMA AOKI ◽

RYO HIGUCHI ◽

TOMOHIRO YOKOZEKI

Keyword(s):

Composite Laminates ◽

Damage Mechanics ◽

Crack Density ◽

Continuum Damage Mechanics ◽

Fatigue Loading ◽

Stiffness Degradation ◽

Cfrp Laminates ◽

Mechanics Model ◽

Element Simulation ◽

Proposed Model

This study aims to conduct a fatigue simulation for predicting the stiffness degradation of thin-ply composite laminates with several ply thicknesses. For the simulation, a fatigue evolution model of intra-laminar damage in thin-ply composite laminates considering the effect of ply thickness was proposed. The intra-laminar damage evolution was modeled using the continuum damage mechanics model and the static and fatigue evolution law were formulated by relating the transverse crack density to the damage variable. The finite element simulation using the proposed model was conducted to predict the stiffness degradation of the laminates as a function of the number of loading cycles. The simulation results show that the experimental data can be reproduced by using the proposed fatigue model.

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