Environmental degradation using functionally graded material approach

Sevostianov, Igor; Sookay, N.K.; Klemperer, C.J. von; Verijenko, V.E.

doi:10.1016/j.compstruct.2003.09.014

Cited by 5 publications

(7 citation statements)

References 7 publications

(9 reference statements)

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“…Note that the three starting knot points are identical as for the three ending knot points. This constrains the B-spline surface to lie on the control points P ij when (i, j) ¼ (1, 1-6), (6,(1)(2)(3)(4)(5)(6), (1)(2)(3)(4)(5)(6)1) or (1)(2)(3)(4)(5)(6)6). The remaining interior control points, hence, do not lie on the B-spline surface.…”

Section: Quadratic Formulation Approachmentioning

confidence: 99%

“…Here a significant amount of epoxy was eroded out during repeated exposures to UV and high humidity. Sevostianov et al [3] have proposed a model to quantify laminate properties due to various extents of environmental damage as the damage tends to progress from the surface to the interior. More recently, Shin and Hahn [4] reported an 18% drop in modulus due to accelerated ageing which includes UV radiation, temperature and moisture.…”

Section: Introductionmentioning

confidence: 99%

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Estimating Surface Damage of Composite Panels with Inverse Analysis

Ramanujam

Nakamura

2007

Journal of Composite Materials

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When composite structures are exposed to harsh environmental conditions or impacted by foreign objects, their surfaces may degrade or damage. Damage evaluations of composite panels often demand expensive tools and time-consuming processes. The aim of this work is to introduce a versatile inverse analysis based method that requires less measurement efforts than those of conventional techniques. In this procedure, first, strains are measured on a surface opposite to damaged surface. Then, general functions relating damage conditions to strain fields are established. These functions reduce computational efforts required during the damage identification. With the measured strains and functions, an error objective function is minimized via iterations to estimate the damage extent. To verify the effectiveness of this proposed procedure, a detailed simulation study is performed with cross-ply composite laminates possessing various damage. The results show excellent matches between the estimated damage fields and the specified conditions imposed on the models. Following this promising outcome, the proof of concept study is extended to several real cross-ply composite panels that are damaged by either sand-blasting or environmental exposure. In the latter case, the composites were exposed to combined ultraviolet radiation and moisture absorption. On composite specimens, spatial variations of strain fields are measured with strip strain-gauges. Then they are used to identify surface damage distributions with either the quadratic formulation or the B-spline method. The latter approach is suitable when the functional change of strains due to damage is not smooth. The results estimated the variation of damage extent in each specimen. This feasibility study clearly supports the possibility of using strain sensor-network or optical method to quantify surface damage.

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Section: Quadratic Formulation Approachmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Estimating Surface Damage of Composite Panels with Inverse Analysis

Ramanujam

Nakamura

2007

Journal of Composite Materials

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“…The target users are the various groups who need to use UV data but do not have the time or experience to use some of the more complex radiative transfer models available. For example, in the building industry (28, 29) it is often necessary to determine the UV exposure a paint, material or finish is likely to receive over its lifetime (30, 31); for biology and health‐related issues knowledge of realistic UV exposure is important (32, 33). There is also the possibility of using the model to estimate the effect on UV of changes in the various input parameters for climatological studies or as a teaching aid.…”

Section: Introductionmentioning

confidence: 99%

A Web‐based Tool for UV lrradiance Data: Predictions for European and Southeast Asian Sites

Kift

Webb

Page

et al. 2006

Photochem & Photobiology

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There are a range of UV models available, but one needs significant pre-existing knowledge and experience in order to be able to use them. In this article a comparatively simple Web-based model developed for the SoDa (Integration and Exploitation of Networked Solar Radiation Databases for Environment Monitoring) project is presented. This is a clear-sky model with modifications for cloud effects. To determine if the model produces realistic UV data the output is compared with 1 year sets of hourly measurements at sites in the United Kingdom and Thailand. The accuracy of the output depends on the input, but reasonable results were obtained with the use of the default database inputs and improved when pyranometer instead of modeled data provided the global radiation input needed to estimate the UV. The average modeled values of UV for the UK site were found to be within 10% of measurements. For the tropical sites in Thailand the average modeled values were within 1120% of measurements for the four sites with the use of the default SoDa database values. These results improved when pyranometer data and TOMS ozone data from 2002 replaced the standard SoDa database values, reducing the error range for all four sites to less than 15%.

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“…This is because in practical applications, the environmental resistance of a laminate is determined by that of its barrier coat, made of a resin rich layer. It is also observed, in general, that the degradation mechanism of FRP initiates in the matrix and primarily affects the matrix dominated properties [14,[16][17]. Therefore, the investigation focuses on the matrix as the latter appears to be the most sensitive part of the composite laminate structure.…”

Section: Introductionmentioning

confidence: 99%

“…This is because it is demonstrated experimentally that the degradation of the mechanical strength of materials used in aviation varies in a layered way after exposure to a natural environment [13]. The degradation process can be considered as a progressing damaged front that moves from the outer surface through the laminate [14]. A gradient is generated through the laminate thickness and because of such a gradient effects on mechanical strength depend strongly on the laminate thickness [13,15].…”

Section: Introductionmentioning

confidence: 99%

Prediction of thermal strains in fibre reinforced plastic matrix by discretisation of the temperature exposure history

Ngoy

2016

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. Prediction of environmental effects on fibre reinforced plastics habitually is made difficult due to the complex variability of the natural service environment. This paper suggests a method to predict thermal strain distribution over the material lifetime by discretisation of the exposure history. Laboratory results show a high correlation between predicted and experimentally measured strain distribution IntroductionDue to the need for energy efficient materials, there has been a considerable increase of interest in light and green materials such as fibre reinforced plastics (FRP) in the aerospace industry. However, environmental effects have shown to be a hindrance to extensive use of FRP. A reliable method to quantify and predict environmental effects on FRP is required for safe and efficient use of these materials.Stresses resulting from environmental factors such as cycling temperature and humidity have been recognised as one of the most deleterious effect on FRP materials [1]. Hygrothermal stresses are known to be the cause for crack initiation and cause the material to become brittle or to deform [2,3]. They can approach or exceed the design load and acceptable material limits [4].A number of works on the modelling of environmental stress effect on FRP material have been reported [5][6][7][8][9][10][11][12]. These reports deal mostly with the characterisation of the effect of temperature and humidity on the stress state of composite laminates. In this regard, models and computation algorithms of various performance levels have been made available. However, most of the time complication results from the material heterogeneity and the complex variability of the environment. In addition, only the effect of the physical degradation is taken into account explicitly, while the material undergoes a chemical degradation also.This analysis focuses on the determination of environmental stresses without involving the resulting modification on the stress state of the material. Attention is on the prediction of a long-term effect, comprehensively taking into account the physical and the chemical degradation, as well as the viscoelastic, time-dependent effect. In the present paper, the thermal strain history is predicted based on the knowledge of temperature exposure. In a subsequent paper, strains will be used to compute stresses taking into account the time dependent relaxation and environmental degradation.For the purpose of this paper, only a one-dimensional problem in plate laminate is considered. This is because it is demonstrated experimentally that the degradation of the mechanical strength of materials used in aviation varies in a layered way after exposure to a natural environment [13]. The degradation process can be considered as a progressing damaged front that moves from the outer

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Environmental degradation using functionally graded material approach

Cited by 5 publications

References 7 publications

Estimating Surface Damage of Composite Panels with Inverse Analysis

Estimating Surface Damage of Composite Panels with Inverse Analysis

A Web‐based Tool for UV lrradiance Data: Predictions for European and Southeast Asian Sites

Prediction of thermal strains in fibre reinforced plastic matrix by discretisation of the temperature exposure history

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