scispace - formally typeset
Search or ask a question
Journal Article•DOI•

A multi-pattern compensation method to ensure even temperature in composite materials during microwave curing process

Jing Zhou1, Yingguang Li1, Nanya Li1, Shuting Liu1, Libing Cheng1, Shaochun Sui, James Gao2 •
Nanjing University of Aeronautics and Astronautics1, University of Greenwich2
01 Apr 2018-Composites Part A-applied Science and Manufacturing (Elsevier)-Vol. 107, pp 10-20
TL;DR: In this article, the authors reveal the one-to-one correspondence between heating patterns of composite parts and microwave curing system settings, and report a new concept to solve this problem by continuously monitoring and compensating the uneven temperature distribution in real-time.
Abstract: Microwave curing technologies have many advantages in manufacturing fiber reinforced polymer composite materials used in aerospace products, compared with traditional autoclave curing technologies. However, the uneven electromagnetic field of microwave in the cavity of the curing chamber results in uneven temperature on the surface of composite laminates during curing, which has been a major obstacle in industrial applications worldwide. Existing methods attempted to solve the problem by the random superposition of uneven electromagnetic fields, but the results were still not satisfactory to meet the high quality requirements of aerospace parts. This paper reveals the one-to-one correspondence between heating patterns of composite parts and microwave curing system settings, and reports a new concept to solve this problem by continuously monitoring and compensating the uneven temperature distribution in real-time. Experimental results from both fiber optical fluorescence sensors and infrared thermal imagers showed significant improvement in temperature uniformity compared with existing methods.

Summary (3 min read)

Jump to: [1. Introduction] – [2. Idea of the multi-pattern compensation method] – [HP (1)] – [3. Implementation of the multi-pattern compensation method] – [3.1 Strategy of HP database construction] – [3.2 Strategy of uneven temperature compensation] – [3.3 Strategy of power control] – [4. The experiment carried out] – [5. Results and discussions] – [5.1 Theoretical analyses of the experimental findings] – [5.2 Validation of the proposed multi-pattern compensating method] and [6. Conclusions]

1. Introduction

  • Fiber reinforced polymer composites with strong mechanical properties are increasingly used in aerospace products [1, 2].
  • The technology has a number of problems which restrict further improvement of product quality and manufacturing efficiency [4].
  • The second way is to use multiple microwave sources within the cavity since the resonant modes associated with different sources are able to overlap, which may further enhance the heating uniformity [23].
  • The purpose of the turning table is to reduce the effect of multiple hot spots by moving the object being heated through areas of high and low power fields alternately, so as to achieve uniformity in temperature of the food.
  • These methods cannot solve the problem from the scientific point of view, and the uneven temperature problem during microwave curing remains as a major challenge in the manufacturing of advanced composite materials [18, 19].

2. Idea of the multi-pattern compensation method

  • Through extensive experimental research, the authors found that there is a one-to-one correspondence between heating patterns (HPs) of composite parts and microwave curing system settings , as illustrated in Fig.1.
  • Corresponding theoretical analysis is presented in Section 5.1.
  • Here, HP are defined as the distribution law of the microwave power on the composite surface, which can be mathematically expressed as a matrix which contains the information of the microwave power and position.

HP (1)

  • Where mnP is the microwave power at a certain point on the composite surface.
  • The MCSS represents a couple of parameters regarding the resonant applicator, the microwave input and the composite part.
  • The position and number of microwave inputs were used as the control strategy of the MCSS, and can be expressed mathematically as a vector.
  • Hence, when a part (or a new one of the same) is heated for a new run, the HPs collected beforehand can be used as a useful database to adjust its uneven temperature distribution.
  • This is the idea of the multi-pattern compensation method.

3. Implementation of the multi-pattern compensation method

  • A process control system is developed to implement the multi-pattern compensation method.
  • As shown in Fig.3, the structure of the system can be divided into two parts.
  • One is aimed at improving the temperature uniformity of the composite part, and the other is to keep the average temperature following the setting temperature.
  • When the curing process is started, the temperature distribution of the part is monitored and analyzed in real time.
  • Once the HP is selected, the computer will rapidly adjust the switches of the magnetrons of the oven according to the related control strategy.

3.1 Strategy of HP database construction

  • Since the microwave power distribution on the composite surface is unmeasurable without disturbing the original microwave field, another physical quantity that is directly proportional to the microwave power has to be used to solve this problem.
  • As for the exothermic heat of cure reaction, it will influence the temperature distribution of the composite during microwave curing, but the temperature distribution is monitored in real-time by temperature sensors, and then a normal compensation process will be carried out.
  • As shown in Fig.4, if only one spot is considered during the compensation process, n HPs are needed to construct the HP database, making this spot, for example hot spot or cold spot, of these HPs spread over the whole surface of the composite part.
  • If not, it is better to make the control strategy programmed so that the computer can continuously execute multiple times in a single cycle for time saving.

3.2 Strategy of uneven temperature compensation

  • During the microwave curing process, the uneven temperature of the composite part is compensated based on the established HP database.
  • Only the hottest spot or the coldest spot was taken into account during one compensation step, considering the compensation accuracy and efficiency at the same time.
  • If max minT-T T-T³ (T , maxT and minT are the average, maximum and minimum of the measured temperature), the hottest spot on the part will be compensated preferentially.
  • Specifically, the computer will search the HP database very quickly for an appropriate HP which has the lowest heating rate at the corresponding position.
  • These monitoring and compensating steps are repeated until the composite part is completely cured.

3.3 Strategy of power control

  • The purpose of the power controller is to keep the measured average temperature tracking the setting temperature.
  • When the total microwave power is determined, the power variation will be equally distributed to the current microwave inputs.
  • When the power of these inputs is increased by pD simultaneously, the heating rate of each area will increase by C , but the HP of the composite (relationship between the heating rates in these areas) will not be changed.

4. The experiment carried out

  • A 2.45GHz, 20KW microwave curing system was designed and manufactured by the research team, as shown in Fig.7 (a).
  • The composite plate was first preheated by various control strategies to construct its HP database.
  • The preset threshold for compensation was set as 6°C, and the operating time of each HP is 8s.
  • The second experiment randomly changed the microwave power of all magnetrons of the oven to generate relative movement between the electromagnetic field and the composite plate, like the commonly used mode agitator or turntable.

5. Results and discussions

  • Based on the authors’ experimental findings, this paper presents a multi-pattern compensation method to realize the uniform in-plane temperature distribution of composite parts during microwave curing.
  • Then, the effectiveness of the proposed multi-pattern compensating method is investigated in detail.

5.1 Theoretical analyses of the experimental findings

  • Since the HP of a composite part is directly affected by the electromagnetic fields inside a microwave oven, the influence of MCSSs on the electromagnetic fields inside the microwave oven is systematically discussed in this section.
  • As shown in Fig.8 (e) and (f), the resonant frequency of the microwave cavity after perturbation can be computed as follows.
  • The 10lTE mode induced by each microwave input in the rectangular oven of where 10lA is an amplitude constant, b is the propagation constant of microwave.
  • Thus, the position and number of microwave inputs, as well as the power ratio between them have significant influence on the distribution of electromagnetic fields in the cavity.
  • This further confirms the authors’ experimental findings of the relationship between composite HPs and MCSSs.

5.2 Validation of the proposed multi-pattern compensating method

  • The temperature distribution on the composite surface under the traditional single pattern heating, random field variation heating and multi-pattern compensation heating was compared by the shown maximum, average and minimum temperature profiles (see Fig.9).
  • Sometimes good results can be obtained, and sometimes the situation is just the opposite.
  • The maximum temperature difference was only 11.2°C, which brings a reduction of about 67% and 58% compared with the traditional single pattern heating and random field variation heating.
  • As a consequence, the temperature distribution during the random field variation heating is more homogeneous than that in the single pattern heating.
  • Then, there was a small overshoot along with the rise of the composite temperature, but it was gradually adjusted back by the system.

6. Conclusions

  • Based on the authors’ experimental findings that there is a one-to-one correspondence between composite HPs and MCSSs, a multi-pattern compensation method was proposed to realize a homogeneous microwave curing process for advanced composite materials.
  • In order to ensure the feasibility of the multi-pattern compensation method, the theoretical analysis of the findings was investigated; the principle of this method was discussed; and the control strategy of this method is designed.
  • It was demonstrated to be a feasible plan through the comparison of resulting temperature difference between this and other two traditional microwave curing process.
  • Under the situation of only considering the hottest spot or the coldest spot during one compensation step, the maximum temperature difference of a short carbon fiber/epoxy composite plate was reduced by 67% and 58% compared with the traditional single pattern heating and random field variation heating process.
  • This technology can be potentially used in other microwave heating processes as well where a high temperature uniformity is required.

Did you find this useful? Give us your feedback

Figures (1)

Content maybe subject to copyright    Report

1
!
A multi-pattern compensation method to ensure even temperature
in composite materials during microwave curing process
Jing Zhou
a
, Yingguang Li*
,a
, Nanya Li
a
, Shuting Liu
a
, Libing Cheng
a
, Shaochun Sui
b
,
James Gao
c
a
College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics
and Astronautics, Nanjing, 210016, China
b
Chengdu Aircraft Industrial (Group) Co., Ltd., Chengdu, 610000, China
c
Faculty of Engineering and Science, University of Greenwich, Chatham Maritime,
Kent, ME4 4TB, UK
Abstract:
Microwave curing technologies have many advantages in manufacturing fiber
reinforced polymer composite materials used in aerospace products, compared with
traditional autoclave curing technologies. However, the uneven electromagnetic field of
microwave in the cavity of the curing chamber results in uneven temperature on the
surface of composite laminates during curing, which has been a major obstacle in
industrial applications worldwide. Existing methods attempted to solve the problem by
the random superposition of uneven electromagnetic fields, but the results were still not
satisfactory to meet the high quality requirements of aerospace parts. This paper reveals
the one-to-one correspondence between heating patterns of composite parts and
microwave curing system settings, and reports a new concept to solve this problem by
continuously monitoring and compensating the uneven temperature distribution in
real-time. Experimental results from both fiber optical fluorescence sensors and infrared
thermal imagers showed significant improvement in temperature uniformity compared
with existing methods.
Key words: A. Polymer-matrix composites (PMCs); D. Process monitoring; E. Out of
autoclave processing; E. Cure.
*Corresponding author at: College of Mechanical and Electrical Engineering, Nanjing
University of Aeronautics and Astronautics, Nanjing, 210016, China.
Tel.: +86 25 84895835; fax: +86 25 84895906.
E-mail address: liyingguang@nuaa.edu.cn (Yingguang Li).
2
!
1. Introduction
Fiber reinforced polymer composites with strong mechanical properties are
increasingly used in aerospace products [1, 2]. According to an investigation recently
carried out in collaboration with Chinese Aircraft Industrial (Group) Co., around 98%
composites used in the aerospace industry are fabricated using autoclave curing
technologies, where the material is placed in a chamber and heated by the circulating
airflow [3]. However, the technology has a number of problems which restrict further
improvement of product quality and manufacturing efficiency [4]. For aerospace
applications, the most important problem is the serious deformation of composites of
large size with varying thickness, due to the large temperature gradient in the thickness
direction. Other problems include long process cycles and high energy consumption [5].
For example, the annual output of the A350XWB will be 156 airplanes after 2018 [6],
thus 312 wings need to be manufactured. For some composite parts, only the curing
process may take up to 24 hours with a maximum energy consumption of 4070KW per
hour for an autoclave of size Ф5m×14m [7, 8], and the part deformation can be very
severe [9]. This cannot meet the increasing demands for large quantity of high
performance composites in modern aircrafts.
As an alternative to traditional autoclave curing technologies, microwave curing
technologies can reduce curing time and energy consumption, and also reduce the
temperature gradient within the composite material during curing. This is because
microwaves can heat the whole volume of the material at the same time [10], thus
greatly reducing the deformation of composite parts and improving the efficiency of the
curing process [11]. To date, a lot of research work had been conducted on microwave
curing of composites materials, including fundamental principles [12], curing kinetics
[13], fiber/matrix interfaces [14], reducing temperature gradient [15] and mechanical
properties [16, 17].
However, microwave curing technologies have not been widely applied in the
aerospace industry because of the difficulties in ensuring an even temperature on the
3
!
surface of composite laminates during curing [18, 19]. The uneven temperature
distribution is caused by the uneven resonance of the electromagnetic field in the cavity
of microwave ovens [20]. Resonance can be considered as the effect where waves are
incident from several directions at the same time. For any arbitrary point in the cavity,
the separate wave fields incident from different directions interfere each other, i.e., they
combine constructively and destructively in an alternating pattern, and form a standing
wave during the superimposition [21]. Over time ‘hot spots’ and ‘cold spots’ (relative to
the hot spots), corresponding to antinodes and nodes of the standing wave will
inevitably appear on the surface of composite materials, leading to the uneven in-plane
temperature distribution. Because composite materials are basically laminated plate
structures, the uneven temperature distribution on their surfaces has a significant impact
on their curing performance, which can directly contribute to severe warpage and even
local ablation or under-treatment.
In order to solve the uneven temperature problem, different ways had been
attempted in the past which can be classified into four categories. The first one is to
focus on the design of the shape and size of the microwave cavity [22]. For example, the
uniformity of the microwave field can be improved by increasing the size of the cavity.
This is because the number of resonant modes (the distribution state of the
electromagnetic field) within a microwave applicator increases rapidly as the size of the
cavity increases, and sometimes the different resonant modes within the applicator are
possible to have complementary effects. The second way is to use multiple microwave
sources within the cavity since the resonant modes associated with different sources are
able to overlap, which may further enhance the heating uniformity [23]. The third way
is to generate a relative movement between the material and the electromagnetic field
[24]. An example can be found in a microwave oven at home which is often equipped
with a turning table that rotates the plate with food during operation. The purpose of the
turning table is to reduce the effect of multiple hot spots by moving the object being
heated through areas of high and low power fields alternately, so as to achieve
uniformity in temperature of the food. The fourth way is to adopt variable-frequency
4
!
microwave systems for materials processing, which can generate many different
resonant modes by repeatedly applying different microwave frequencies thus achieving
uniformity of power within the microwave cavity [25, 26].
The above existing methods have, to different extents, improved the uniformity of
microwave heating by random superposition of the uneven electromagnetic field within
the microwave cavity. However, these methods cannot solve the problem from the
scientific point of view, and the uneven temperature problem during microwave curing
remains as a major challenge in the manufacturing of advanced composite materials [18,
19]. This paper reveals the relationship between heating patterns of composite parts and
microwave curing system settings. On this basis, a multi-pattern compensation method
is proposed to achieve better uniformity of temperature on the surface of composite
laminates during microwave curing. This method, through monitoring the uneven
temperature distribution and applying appropriate compensating HPs in real-time, can
significantly improve the homogeneity of the temperature field of composite parts
during curing.
2. Idea of the multi-pattern compensation method
Through extensive experimental research, the authors found that there is a
one-to-one correspondence between heating patterns (HPs) of composite parts and
microwave curing system settings (MCSSs), as illustrated in Fig.1. Corresponding
theoretical analysis is presented in Section 5.1. Here, HP are defined as the distribution
law of the microwave power on the composite surface, which can be mathematically
expressed as a matrix which contains the information of the microwave power and
position.
11 12 1
21 22 2
12
n
n
mm mn
PP P
PP P
PP P
éù
êú
êú
=
êú
êú
ëû
HP
(1)
where
mn
P
is the microwave power at a certain point on the composite surface. The
5
!
MCSS represents a couple of parameters regarding the resonant applicator, the
microwave input and the composite part. Among them, parameters of the composite part
(material, ply, shape, size and position) and the microwave equipment (shape, size,
filling medium of the applicator, and frequency of the microwave input) can be regarded
as constants and are difficult to be adjusted during curing, when a certain composite part
and a certain industrial microwave oven (often with multiple microwave magnetrons)
are selected. Fortunately, the position and the number of microwave inputs, as well as
the power ratio between them can be easily controlled by adjusting the switches of
various magnetrons of the oven as an electronic process. In this paper, the position and
number of microwave inputs were used as the control strategy of the MCSS, and can be
expressed mathematically as a vector.
[ ]
12
,,
l
dd d
=MCSS
(2)
where
l
d
is the switch state of the lth microwave input, which is a binary number and
can be valued at 0 or 1. As mentioned above, the heating pattern of the composite can be
controlled by adjusting the control strategy of the MCSS.
( )
f =MCSS HP
(3)
According to the above analysis, the HP of the object being heated will not change
as long as the related MCSS remains constant. Hence, when a part (or a new one of the
same) is heated for a new run, the HPs collected beforehand can be used as a useful
database to adjust its uneven temperature distribution. More specifically, when a certain
temperature distribution is monitored, a HP with a complementary heating preference
would be most beneficial to realize a uniform in-plane temperature distribution,
especially when the high/low power sections of the HP are cold/hot spots for the current
temperature distribution (see Fig.2). This is the idea of the multi-pattern compensation
method. It overcomes the limitation of random superposition principle in traditional
method, and use complementary HPs to ensure even curing temperature during the
whole curing process.
Citations
More filters
Journal Article•DOI•
Indirect Microwave Curing Process Design for Manufacturing Thick Multidirectional Carbon Fiber Reinforced Thermoset Composite Materials

[...]

Jing Zhou1, Yingguang Li1, Libing Cheng1, Linglin Zhang1•
Nanjing University of Aeronautics and Astronautics1
01 Apr 2019-Applied Composite Materials
TL;DR: In this paper, a multiphysics model was constructed to reflect the composite curing behavior in a cost-effective manner, which agreed well with the experimental results, and a new indirect microwave curing cycle was designed, and relevant process parameters were determined.
Abstract: Recently, indirect microwave curing technology was developed to process multidirectional carbon fiber reinforced composite materials with high efficient and energy saving purpose. The aim of this paper is to solve the problem of large mid-plane heat generation in manufacturing this kind of materials with large thickness. The difference between the traditional thermal curing and indirect microwave curing processes was analyzed. A Multiphysics model was constructed to reflect the composite curing behavior in a cost-effective manner, which agreed well with the experimental results. On this basis, a new indirect microwave curing cycle was designed, and relevant process parameters were determined. Compared with the manufacturer’s recommended cycle, the degree of mid-plane heat generation was greatly relieved, and a reduction of 34.6% in composite residual strains was achieved. Moreover, the curing cycle was reduced by 38%, while the interlaminar shear strength of the composite was improved by 1.38 times. Corresponding reinforcement mechanisms were explored through the observation of composite cross-sections with optical microscopes.

16 citations

Journal Article•DOI•
Online learning based intelligent temperature control during polymer composites microwave curing process

[...]

Zhou Jing1, Li Yingguang1, Di Li1, Youyi Wen•
Nanjing University of Aeronautics and Astronautics1
15 Aug 2019-Chemical Engineering Journal
TL;DR: In this article, neural networks were used to learn the dynamic temperature behaviors of the composite under various microwave control strategies during curing, which continuously provided accurate solutions to the uneven temperature distribution monitored in real time by active compensation.

15 citations

Journal Article•DOI•
Microwave processing of carbon fibre polymer composites: a review:

[...]

Joel Galos1•
RMIT University1
01 Mar 2021-Polymers & Polymer Composites
TL;DR: Microwave processing of carbon fiber-reinforced polymer (CFRP) composites is gaining increasing attention as an alternative to conventional thermal processing techniques as mentioned in this paper, which has the potential to re...
Abstract: Microwave processing of carbon fibre-reinforced polymer (CFRP) composites is gaining increasing attention as an alternative to conventional thermal processing techniques. It has the potential to re...

12 citations

Additional excerpts

  • ...The variation in dielectric properties throughout the curing process can be exploited via in situ monitoring of the cure to optimize the use of microwaves during processing.(10,17) To this end, Zhang et al....

    [...]

Journal Article•DOI•
Micro-flow sensor for continuous resin fluidity monitoring between fibers

[...]

Yongxi He1, Yingguang Li1, Xiaozhong Hao1, Jing Zhou1, Shuting Liu1 •
Nanjing University of Aeronautics and Astronautics1
01 Mar 2019-Sensors and Actuators B-chemical
TL;DR: In this article, a step-changing difference of capillary pressure was proposed for the micro-flow measurement between reinforced fibers in fiber reinforced polymer (FRP) composites, and a highly sensitive and calibration-free microflow sensor was designed by simply introducing an optical fiber with super-infiltration polyimide coating along the reinforced fibers.
Abstract: The resin micro-flow between fibers influences bubble evacuation and fiber impregnation during the processing of fiber reinforced polymer (FRP) composites. The trapped bubbles and unimpregnated regions within a laminate will develop into voids after the processing, which will impair the structural performance severely. In this study, a new sensing principle of the step-changing difference of capillary pressure was proposed for the micro-flow measurement between reinforced fibers in FRP composites. A highly sensitive and calibration-free micro-flow sensor was designed by simply introducing an optical fiber with super-infiltration polyimide coating along the reinforced fibers. The FRP composite around the optical fiber was regarded as part of the sensing structure. The key resin flow states between fibers were first detected continuously during composite processing.

10 citations

Journal Article•DOI•
Analysis and control of cured deformation of fiber-reinforced thermosetting composites: a review

[...]

Jiaoyuan Lian1, Zhongbin Xu1, Xiaodong Ruan1•
Zhejiang University1
01 May 2019-Journal of Zhejiang University Science
TL;DR: In this article, the authors discuss the latest achievements relating to cured deformation mechanisms, prediction models, and control strategies in fiber-reinforced material fields, and propose five main control strategies: die surface compensation, process optimization, structural optimization, tool part contact optimization, and development of other methods.
Abstract: Fiber-reinforced thermosetting composites are of great significance in aerospace, marine, automotive, wind power, and civil engineering fields. They have outstanding advantages and can reduce weight and enhance performance, especially by replacing steel pieces. However, nonreversible cured deformation is an obstacle to the rapid development of these composite components. Studies in this field typically focus on the numerical prediction of the effects of cured deformation on composite components, which helps engineers design and modify the mold to compensate for deformation. In this review we discuss the latest achievements relating to cured deformation mechanisms, prediction models, and control strategies in fiber-reinforced material fields. In particular, different intrinsic and extrinsic factors that affect cured deformation are summarized and five main control strategies are proposed: die surface compensation, process optimization, structural optimization, tool-part contact optimization, and development of other methods. In addition, the effects of these factors on controlling deformation are compared. Unlike previous studies, this study integrates control strategies and the main mechanisms involved to achieve a more comprehensive view of cured deformation in thermosetting composites.

10 citations

References
More filters
Journal Article•DOI•
Microwave processing: fundamentals and applications

[...]

Erik T. Thostenson1, Tsu-Wei Chou1•
University of Delaware1
01 Sep 1999-Composites Part A-applied Science and Manufacturing
TL;DR: In this paper, the fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article, and a knowledge of electromagnetic theories and dielectrics is essential to optimize the processing of materials through microwave heating.
Abstract: In microwave processing, energy is supplied by an electromagnetic field directly to the material. This results in rapid heating throughout the material thickness with reduced thermal gradients. Volumetric heating can also reduce processing times and save energy. The microwave field and the dielectric response of a material govern its ability to heat with microwave energy. A knowledge of electromagnetic theory and dielectric response is essential to optimize the processing of materials through microwave heating. The fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article.

1,296 citations

Journal Article•DOI•
Interfacial Microstructure and Properties of Carbon Fiber Composites Modified with Graphene Oxide

[...]

Xiaoqing Zhang1, Xinyu Fan1, Chun Yan1, Hongzhou Li1, Yingdan Zhu1, Li Xiaotuo1, Yu Liping1 •
Chinese Academy of Sciences1
13 Mar 2012-ACS Applied Materials & Interfaces
TL;DR: An alternative method for improving the interfacial and tensile properties of carbon fiber composites by controlling the fiber-matrix interface was developed and such multiscale reinforced composites show great potential with their improved mechanical performance to be likely applied in the aerospace and automotive industries.
Abstract: The performance of carbon fiber-reinforced composites is dependent to a great extent on the properties of fiber–matrix interface. To improve the interfacial properties in carbon fiber/epoxy composites, we directly introduced graphene oxide (GO) sheets dispersed in the fiber sizing onto the surface of individual carbon fibers. The applied graphite oxide, which could be exfoliated to single-layer GO sheets, was verified by atomic force microscope (AFM). The surface topography of modified carbon fibers and the distribution of GO sheets in the interfacial region of carbon fibers were detected by scanning electron microscopy (SEM). The interfacial properties between carbon fiber and matrix were investigated by microbond test and three-point short beam shear test. The tensile properties of unidirectional (UD) composites were investigated in accordance with ASTM standards. The results of the tests reveal an improved interfacial and tensile properties in GO-modified carbon fiber composites. Furthermore, significa...

561 citations

"A multi-pattern compensation method..." refers background in this paper

  • ...Fiber reinforced polymer composites with strong mechanical properties are increasingly used in aerospace products [1, 2]....

    [...]

Journal Article•DOI•
Microwave–material interaction phenomena: Heating mechanisms, challenges and opportunities in material processing

[...]

Radha Raman Mishra1, Apurbba Kumar Sharma1•
Indian Institute of Technology Roorkee1
01 Feb 2016-Composites Part A-applied Science and Manufacturing
TL;DR: In this paper, most of the significant phenomena that cause heating during microwave-material interaction and heat transfer during microwave energy absorption in materials are discussed. But, the mechanisms associated with the processing are less understood; popular mechanisms such as dipolar heating and conduction heating have been mostly explored.
Abstract: Efforts to use microwaves in material processing are gradually increasing. However, the phenomena associated with the processing are less understood; popular mechanisms such as dipolar heating and conduction heating have been mostly explored. The current paper reviews most of the significant phenomena that cause heating during microwave–material interaction and heat transfer during microwave energy absorption in materials. Mechanisms involved during interaction of microwave with characteristically different materials – metals, non-metals and composites (metal matrix composites, ceramic matrix composites and polymer matrix composites) have been discussed using suitable illustrations. It was observed that while microwave heating of metal based materials is due to the magnetic field based loss effects, dipolar loss and conduction loss are the phenomena associated with the electric field effects in microwave heating of non-metals. Challenges in processing of advanced materials, particularly composites have been identified from the available literature; further research directions with possible benefits have been highlighted.

502 citations

DOI•
An integrated model of the development of process-induced deformation in autoclave processing of composite structures

[...]

Andrew Allen Johnston1•
University of British Columbia1
01 Jan 1997
TL;DR: Sommaire et al. as mentioned in this paper developed a two-dimensional finite element model for prediction of process-induced deformation and integration of this model with analyses for heat transfer and resin cure and resin flow allows analysis of all major identified deformation sources.
Abstract: Manufacture of large composite structures presents a number o f challenges, one of the most critical o f which is prediction and control of process-induced deformation. Traditional empirical techniques for tooling and process cycle development are particularly unsuitable for large parts, especially when development costs and process variability are key issues. Thus, there is a critical need to supplement current techniques with a science-based manufacturing approach. In the present work, a two-dimensional finite element model for prediction of process-induced deformation has been developed. Integration of this model with analyses for heat transfer and resin cure and resin flow allows analysis of all major identified deformation sources. A 'virtual autoclave' concept is employed in which autoclave control algorithms and autoclave response are simulated to predict structure boundary conditions during processing. Characterization of a carbon fibre/epoxy composite is performed and models developed to describe material behaviour during processing. A n examination of autoclave heat transfer is also performed and a model developed for the observed effect of pressure on heat transfer rates. Using these data as inputs, the process model is demonstrated through application to three case studies of varying complexity. In each, model predictions are compared to experimental results and the predicted sensitivity o f processing outcomes to process parameter variation is examined. A good match between model predictions and experimental results was obtained in most cases. The developed model is expected to perform two complementary roles. First, the ability to analyse structures of practical size and complexity makes the model a potentially useful process-development tool for the industrial composites processor. Also, the integration of analyses for all major deformation sources allows examination of parameter interaction, potentially driving fundamental research into deformation mechanisms and the development of improved material behavioural models. Sommaire La fabrication de larges structures en composites comporte de nombreux defis dont l'un des plus critiques est la determination et le controle de la deformation induite durant le procede de fabrication. Dans une optique de reduction des couts de fabrication et des variations de qualite, les methodes empiriques traditionnellement utilisees pour la determination du cycle de cure et la conception de l'outillage sont particulierement inefficaces dans le cas de pieces aux dimensions importantes. Ainsi, il est necessaire de complementer les methodes actuelles par une approche scientifique aux problemes de production. Dans ce travail, un modele d'elements finis en deux dimensions calculant les deformations induites durant la fabrication a ete developpe. Ce modele permet l'analyse des principaux phenomenes contribuant aux deformations en combinant les effets du transfert de chaleur, de la polymerisation de la resine et de l'ecoulement de la resine. Un concept de "l'autoclave virtuel", dans lequel les algorythmes de controle de l'autoclave et la reponse de l'autoclave sont simules, est inclus afin de predire plus precisement les conditions frontieres de la piece durant la fabrication. Un composite fibre de carbone-epoxy est caracterise et des modeles decrivant son comportement au cours de la polymerisation sont developpes. Les caracteristiques du transfert de chaleur de l'autoclave sont determinees et un modele reliant Feffet de la pression sur le coefficient de transfert de chaleur de l'autoclave est developpe. En utilisant ces donnees, la performance du modele d'elements finis est demontree a travers trois cas ayant differents degres de complexite. Pour chacun des cas, les predictions du modele sont comparees aux resultats experimentaux. Sommaire L'effet de la variation des entrees du modele sur la stabilite des parametres du procede est egalement etudie. En general, les resultats experimentaux et numeriques concordent bien. Le modele developpe repond a deux besoins complementaires. D'une part, il est un outil pratique pour le manufacturier de pieces en composites, car il permet d'analyser des structures aux formes complexes et de grandes dimensions. D'autre part, il permet d'analyser l'interaction des parametres, car il integre les principaux mecanismes qui induisent des deformations. Ceci permettra d'encourager la progression de la recherche fondamentale sur les mecanismes causant les deformations et de developper de meilleurs modeles decrivant le comportement du materiau.

219 citations

"A multi-pattern compensation method..." refers background in this paper

  • ...For some composite parts, only the curing process may take up to 24 hours with a maximum energy consumption of 4070KW per hour for an autoclave of size Ф5m×14m [7, 8], and the part deformation can be very severe [9]....

    [...]

Journal Article•DOI•
Comparison of the mechanical and physical properties of a carbon fibre epoxy composite manufactured by resin transfer moulding using conventional and microwave heating

[...]

D A Papargyris1, Richard J. Day1, Alan Nesbitt1, D Bakavos1•
University of Manchester1
01 Jun 2008-Composites Science and Technology
TL;DR: In this paper, microwave heating was incorporated into the resin transfer molding technique, and a 50% cure cycle time reduction was achieved by using carbon fiber/epoxy composites.

131 citations

Related Papers (5)
Online learning based intelligent temperature control during polymer composites microwave curing process

[...]

15 Aug 2019-Chemical Engineering Journal
Zhou Jing, Li Yingguang, Di Li, Youyi Wen 
Microwave curing of carbon–epoxy composites: Penetration depth and material characterisation

[...]

01 Aug 2015-Composites Part A-applied Science and Manufacturing
M. Kwak, Paul Robinson, Alexander Bismarck, R. Wise 
Microwave processing: fundamentals and applications

[...]

01 Sep 1999-Composites Part A-applied Science and Manufacturing
Erik T. Thostenson, Tsu-Wei Chou
Analysis and optimization of temperature distribution in carbon fiber reinforced composite materials during microwave curing process

[...]

01 Mar 2014-Journal of Materials Processing Technology
Nanya Li, Yingguang Li, Xiang Hang, James Gao 
Microwave–material interaction phenomena: Heating mechanisms, challenges and opportunities in material processing

[...]

01 Feb 2016-Composites Part A-applied Science and Manufacturing
Radha Raman Mishra, Apurbba Kumar Sharma