Residual stresses created during curing of a polymer matrix composite using a viscoelastic model

Zhang, Jiang Tao; Zhang, Mei; Li, Shuxin; Pavier, Martyn J; Smith, David J.

doi:10.1016/j.compscitech.2016.05.002

Cited by 57 publications

(32 citation statements)

References 25 publications

(25 reference statements)

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“…Over the years, several studies have reported that the appearance of residual stresses associated with the curing process of composite materials may affect the mechanical performance of composites [7][8][9][10]. According to Hosseini-Toudeshky and Mohammadi, it is important to note that these stresses are the result of the inhomogeneity of the material and its anisotropic behavior, which is evident from the differences that exist in Young's modulus values and the thermal expansion coefficient of the constituent materials of the composite [11].…”

Section: Structural Elements Made From Laminated Compositementioning

confidence: 99%

Influence of thermal residual stresses on the free vibration of reinforced laminates

Sánchez

Capote

Carrillo

2017

DYNA

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The use of laminated composite materials has increased in modern engineering, mainly in those projects that require an assurance of good strength and durability. It has been found that some properties of the material that ensure proper performance can be affected by the occurrence of residual stresses caused by the manufacturing process. In this paper, the influence of thermal residual stresses on the free vibration of reinforced plates is analyzed. For the experimental study, a square, reinforced, prepreg laminate was used. The laminate was reinforced using two different types of reinforcement: lateral and perimetral. The plates were prepared using two different techniques. The first group of laminates was prepared by curing the reinforcement at 177 °C. The second group of laminates was prepared by secondary bonding of the reinforcement to the laminate at room temperature (22 °C). A numerical model was elaborated for comparison with the experimental results. Accuracy was observed when comparing experimental and numerical results, showing that the presence of residual thermal stress affects the value of the natural frequencies of free vibration and the characteristic modal form of reinforced plates. Regardless of the type of reinforcement used, a notable increase in these values was observed, even when the element was simply supported.Keywords: Laminates; thermal stresses; free vibration; frequency; cure temperature.Influencia de las tensiones térmicas residuales en la vibración libre de laminados reforzados Resumen El uso de compuestos laminados se ha incrementado en la ingeniería moderna, fundamentalmente en proyectos en los cuales se requiere garantizar una adecuada resistencia y durabilidad. Se ha comprobado que algunas de las propiedades del material pueden ser afectadas por la aparición de tensiones residuales durante el proceso de manufactura. En este artículo, la influencia de las tensiones térmicas residuales en la vibración libre de compuestos laminados es analizada. Para el estudio experimental se empleó un laminado cuadrado de tipo pre-impregnado. El laminado fue reforzado usando dos tipos de refuerzos: laterales y perimetrales. Las placas fueron elaboradas usando dos diferentes técnicas: el primer tipo de laminados fue elaborado curando tanto la placa como los refuerzos a 177 °C de manera simultánea y posteriormente enfriados a la temperatura de servicio, mientras que para el segundo tipo de placas tanto las láminas como los refuerzos fueron preparados de forma independiente y pegados a temperatura de operación (22 °C). Un modelo numérico fue elaborado para comparar estos resultados con los resultados experimentales. Una buena precisión fue observada al comparar resultados numéricos y experimentales, mostrando que la presencia de tensiones térmicas residuales afecta el valor de las frecuencias naturales de vibración libre y la forma modal característica. Independientemente del tipo de refuerzo empleado, un notable incremento en estos valores fue observado, cuando el elemento se encuentra sim...

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Section: Structural Elements Made From Laminated Compositementioning

confidence: 99%

Influence of thermal residual stresses on the free vibration of reinforced laminates

Sánchez

Capote

Carrillo

2017

DYNA

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“…Due to the high differences in structure of fibres, the relaxation behaviour could be different and it is especially visible for woollen fibres, as the protein fibres have an even more complex physical and chemical structure. Therefore, it was found that the stress relaxation behaviour in long-lasting relaxation (more than 10,000 s) exhibits some difference from the behaviour in a short time relaxation [2,8,13,16,[23][24][25][26][27][28][29]32]. The stress relaxation in initial time of relaxation can …”

Section: Methodsmentioning

confidence: 99%

“…[27][28][29][30][31][32], various properties of relaxation, such as creep, inverse stress relaxation of various types of yarns and fibres (even such as carbon nanotube (CNT) yarns) were investigated. Zhang et al [27] showed that CNT yarns have a resistance against creep and stress relaxation. They found that the stress relaxed less than 15% when a two-ply nanotube yarn was held for 20 h at 6% strain, and the majority of the stress relaxation occurred within the first 20 min.…”

Section: Methodsmentioning

confidence: 99%

Behaviour of Long-Lasting Stress Relaxation of Various Types of Yarns

Laureckienė

Milašius

2017

Autex Research Journal

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The main goal of this researcher is estimating of the possibility of long-lasting (even until 200,000 s) stress relaxation by empirical investigation, which was performed for a few thousands of seconds. The empirical investigations of longlasting stress relaxation of different types of yarns (multifilament polyester, cotton and woollen) at different levels of elongation, i.e. at 3%, 5%, 7% and 10%, were carried out. The method of long-lasting relaxation behaviour prediction by the break-point of relaxation rate as well as the linear dependence of second part of relaxation were used. It was found that the behaviour of relaxation can be described using time logarithmic scale by two straight lines, and the value of stress relaxation in long time period could be estimated by the second line. The break-point of relaxation rate of all kinds of yarns occurs in the area of 100-200 s after relaxations started. The obtained results showed that the place of relaxation break-point depends on the level of elongation but does not depend on the type of yarns.

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“…Significant cost reduction is possible if only the constituent materials are fully characterized and the composite properties are predicted using multi-scale models.At small strains, creep, relaxation, and strain rate dependence of polymer resins are well described by viscoelastic models of the generalized Maxwell type [23,14,15,16]. This kind of model was used by several authors to simulate the generation of residual stresses in composites with both thermosetting and thermoplastic polymer matrices [24,25,26,20,27]. In all these works, the time-temperature superposition principle used, as it was shown to describe well the temperature dependence of the viscoelastic behavior of polymers [14,15,16,28].…”

mentioning

confidence: 99%

“…In all these works, the time-temperature superposition principle used, as it was shown to describe well the temperature dependence of the viscoelastic behavior of polymers [14,15,16,28]. The influence of the degree of cure was introduced in some works as an explicit dependence of the relaxation times on degree of cure [14,16,27], but it can also be modeled through a cure dependent T g used as reference temperature in the time-temperature superposition principle [15,25,28,29].In the present study we focus on composites with 3D woven reinforcements [30,31,32]. This type of composites became an interesting option for industrial applications since the development of modern looms capable of weaving complex reinforcement structures [30,31].…”

mentioning

confidence: 99%

Multi-scale modeling of the viscoelastic behavior of 3D woven composites

Hirsekorn

Marcin

Godon

2018

Composites Part A: Applied Science and Manufacturing

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A method is presented to predict numerically the homogenized viscoelastic behavior of 3D woven composites using only its constituents' behavior. It is based on elastic homogenizations applied to the Laplace-Carson transform of the time-dependent viscoelastic behavior of the constituents. Two scale chages are necessary: from micro-to meso-scale to obtain the homogenized behavior of the consolidated yarns, and from mesoto macro-scale. The temperature and cure dependent viscoelastic behavior of the matrix is identified from experimental data, using the time-temperature superposition principle with the cure dependent glass transition temperature as reference temperature. The meso-scale representative unit cell of the composite is extracted from X-ray microtomography images. The homogenized viscoelastic behavior is used to calculate the evolution of the apparent moduli of the composite with temperature between −50 • C and 200 • C. The results are in good agreement with experimental data over the temperature range where the matrix behavior was properly identified.While the mechanical behavior of carbon or glass fibers is linear elastic in a good approximation and almost independent of temperature, at least below the glass transition temperature (T g ) of typical thermosetting polymers (usually not exceeding about 200 • C), the mechanical behavior of the polymer matrix depends strongly on temperature and on the degree of cure [14,15,16,17,18,12]. Moreover, it is time dependent, i.e., creep and relaxation phenomena are observed, which may have a significant impact on the residual stresses and the final shape of composite parts [13,19,20,21]. As a consequence, residual stresses can be reduced by adapting the cure cycle such that relaxation phenomena are intensified [13,22].Since in the aeronautical industry highly precise part shapes are required, it is currently common practice to adapt the mold shape several times until the composite part fits the shape tolerances. This procedure of designing a composite part is very expensive, but can be greatly optimized if precise modeling tools are available that predict the generation of residual stresses and the final shape of composites with complex reinforcements, such as three-dimensional (3D) interlock weavings. To improve the accuracy of currently available modeling tools, it is necessary to take into account creep and relaxation and their dependence on temperature and degree of cure during the modeling of the curing and cooling process. The experimental characterization of a composite material required to determine the model parameters is complex and expensive, as 3D strain rate, temperature, and cure dependent mechanical behaviors have to be measured. Furthermore, these properties have to be re-identified, each time the reinforcement architecture is changed. Significant cost reduction is possible if only the constituent materials are fully characterized and the composite properties are predicted using multi-scale models.At small strains, creep, relaxation, and strain rate d...

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Residual stresses created during curing of a polymer matrix composite using a viscoelastic model

Cited by 57 publications

References 25 publications

Influence of thermal residual stresses on the free vibration of reinforced laminates

Influence of thermal residual stresses on the free vibration of reinforced laminates

Behaviour of Long-Lasting Stress Relaxation of Various Types of Yarns

Multi-scale modeling of the viscoelastic behavior of 3D woven composites

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