Research on VARTM Technology for fabricating Basalt fiber/vinyl ester

composites

Zuli Sun1, a, Mingen Guo2,b and Zhining Yu2,c 1Science and Engineering College of Chemistry and Biology, Yantai University, Yantai, China

2School of Mechatronic and automobile Engineering, Yantai University, Yantai, China

asunzuli98@163.com,

bguo_ming_en@163.com,

cznyyd@tom.com

Keywords: Basalt fiber/ vinyl ester composites, VARTM, injection strategy, air release additive.

Abstract. Basalt fiber has good sea water resistance, heat resistance and sound insulation. This shows

that, basalt fiber is ideal material for ship manufacturing. Because of the bad fiber permeability, using

VARTM process to produce large basalt fiber marine components still has deficiency. Taking basalt

fiber/vinyl resin composite shell as object, research was taken to find the method of improving resin

flow velocity and suitable resin injection strategy system in VARTM process. The results show that

air release additive contributes to the resin’s flow in preform body, and the tensile strength and

flexural strength of components increase with the increase of air release additive’s quantum when the

quantum less than 0.5%. The resin flow’s frontier of the components made by sequence injection

strategy is always keeping the same and its velocity is uniform, which makes its quality is better than

that made by embranchment injection strategy.

Introduction

VARTM (Vacuum Assisted Resin Transfer Molding) is a low cost composites molding technology,

which has a sharp decline compared with RTM (Resin Transfer Molding) by using single rigid mold.

And compared with hand lay-up molding technology, VARTM has advantages on environmental

protection and high quality components, which makes it more and more application in preparation of

ship shell, fan blade, and large composite components with added core and added reinforcing plate

[1]. The basic processes of VARTM were: laid dry state fiber reinforced material on the molding

surface of rigid mold to form preform body, covered the vacuum bag membrane upon preform body

as upper mode, sealed the rigid mold and vacuum bag membrane into closed cavity with adhesive

tape, vacuumed the cavity, while resin was injected into the cavity and infiltrated preform body under

the vacuum action, cured preform body under room temperature and vacuum pressure completely,

obtained composites component after demoulding [2].

Basalt fiber has better mechanical properties, better sea water resistance and sound insulation

compared with glass fiber, which is ideal raw material for ship manufacturing [3][ 4]. But because of

the bad permeability, using basalt fiber to produce large basalt fiber marine components with

VARTM process is still a rare thing [5]. Focused on VARTM process, took basalt fiber/vinyl resin

composites shell as object, researches were taken to find resin flow improving measures and resin

injection strategy system with less dry spot defects, quick mold filling and good infiltrating effect.

Experiments

Raw materials and processes. The raw materials used in experiments were shown in Table 1. In

which, basalt fiber fabric was 0°/90° and ±45° fabric, with density 400g/m2.

Experimental facility has been shown in Fig.1. Preform body was formed by layers according to

the sequence of 0°/90°, + 45° and -45°. Under the vacuum pressure drive, resin contained 1.2% curing

agent and 0.2% accelerating agent resin came into cavity. After mold filling process, continued to

keep room temperature and pressure to cure 24 hours.

Applied Mechanics and Materials Vols. 268-270 (2013) pp 19-22Online available since 2012/Dec/27 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMM.268-270.19

All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 141.213.236.110, University of Michigan Library, Media Union Library, Ann Arbor, United States of America-17/06/13,08:56:34)

Table 1 Raw materials

Name Basalt fiber

fabric

Vinyl ester Curing

agent

Accelerating

agent

Air release

additive

Specification B400 AME6000 M50 DY7-3 BYK -A560

Manufacturer CPIC Ashland Akzo

Nobel N.V

Wuxi

DYHG

BYK-Chemie

GmbH

Fig.1 Schematic view of vacuum assisted resin transfer molding process

Experimental methods. Enhance the resin fluidity. In order to enhance the resin flow velocity in

basalt preform body, resin with 0.5% quantum of air release additive was compared with resin

without air release additive. In order to assess the effect of air release additive on the composites

property, 0.0, 0.2, 0.3, 0.4, 0.5 and 0.6% quantum of air release additive were distributed into resin

separately, then tested the mechanical properties of component. Tensile strength and bending strength

were separately taken on universal material testing machine WDW-200 according to GB/T1447-2005

and GB/T1449-2005 standards. Composites component were prepared as length, width and thickness

1000∗700∗40 mm.

Resin injection strategy system. Sequence injection strategy and embranchment injection strategy

were tested in experiments. Schematic diagram of sequence injection strategy was shown in the left

side of Fig.2 (a). Schematic diagram of embranchment injection strategy was shown in the right side.

The implementation of sequence injection strategy was shown in Fig.2 (b). The pipes in sequence

injection strategy test were set parallel along with the length direction. When the resin flew a little

ahead of the second pipe, then closed the first pipe while opened the second pipe. While in

embranchment injection strategy a competent pipe was set along the length direction, branch pipes

were connected to the competent pipe and paralleled to each other. Resin flew in the competent pipe

and numbers of branch pipes at the same time.

Fig.2 Schematic diagram of sequence and embranchment injection strategy

20 Materials, Mechanical Engineering and Manufacture

Results and discussion

The resin flow distance-time curve of the component’s bottom layer has been shown in Fig.3. The

flow velocity of resin with air release additive is 9% or so faster than that of resin without air release

additive. It shows that adding air release additive can decrease the operation time, in favor of

infiltrating the preform body before solidification, which can guarantee the quality of large

components molding. The effect of air release additive’s quantum on component’s tensile and

flexural strength has been shown in Fig.4. Adding air release additive can enhance resin’s tensile and

flexural strength, whose reason is that: air release additive can effectively eliminate the volatilized air

in resin and resident air in preform body, increasing the components’ density and the fiber content to

enhance components’ mechanical properties [6]. With the increase of air release additive’s quantum,

tensile and flexural strength also improve. When quantum of air release additive achieves 0.4% and

0.5%, flexural strength and tensile strength reaches apex respectively. Too much air release additive

adverse to the combination surface between resin and fiber, so as to decrease the flexural strength and

tensile strength.

Fig.3 Resin flow velocity contrast figure Fig.4 Air release additive’s effect on mechanical properties

Table 2 Statistics of dry spots and void contents

Name of

defects

Dry spots

[%]

Coefficient

of Variance

[%]

Resin

enrichment

[%]

Coefficient

of Variance

[%]

Void

contents

[%]

Coefficient

of Variance

[%]

Sequence

injection

3.2 8.8 2.5 7.5 1.6 9.2

Embranchment

injection

3.6 10.2 3.1 9.7 1.7 8.9

The experimental conditions of the resin injection strategy system test were: vacuum pressure

95kpa, environment humidity 60%, environment temperature 15℃, resin temperature 20℃.

Composites component was prepared as length, width and thickness 1000*700*40 mm. Sample areas

were uniformly distributed in the whole component. Each sample was 200*200 mm. Defect

assessment items were dry spot, resin enrichment and micro pore. The diameter of the micro defects

was defined as 1 mm or less. The percentage of defect areas in total areas was tested. Image

processing technology was used to analysis and do statistics on micro pore defects based on image

obtained from optical microscope. The average results of defects assessment has been shown in Table

2. The results show that defects by sequence injection strategy are less than those by embranchment

injection strategy. The reason is that: during sequence injection strategy, the frontier of resin flow is

always keeping the same and its velocity is uniform, which can inhibit defect formation. During

embranchment injection strategy, the resin flow frontiers will appear butt state, which is easy to form

the air package, and easy to make macro and micro flow mismatching [7]. Dry spot is shown in Fig.5

(a) and micro pore is shown in Fig.5 (b).

Applied Mechanics and Materials Vols. 268-270 21

Fig.5 Dry spots and void contents in composites

Summary

VARTM process has obviously influence on composite components. Through experiments, some

conclusions have been researched:

For large basalt composite components, those made by sequence injection strategy have better

quality than those made by embranchment injection strategy. The resin flow’s frontier of sequence

injection strategy is always keeping the same and its velocity is uniform. During embranchment

injection strategy, the resin flow frontiers will appear butt state, which is easy to form the air package,

and hard to match macro and micro flow.

Resin with air release additive has a faster flow velocity than that without air release additive in

preform body.

Quantum of air release additive has influence on component’s tensile strength and flexural

strength. The tensile strength and flexural strength of components increase with the increase of air

release additive quantum when the quantum less than 0.5%. But tensile strength and flexural strength

will decrease when the quantum more than 0.5%.

Acknowledgements

This work was financially supported by the National High Technology Research and Development

Program("863"Program) of China (2007AA03A229).

References

[1] W.D. Brouwer, E.C.F.C. van Herpt, M. Labordus.Vacuum injection moulding for large structural

applications . Composites: Part A 34 (2003) 551–558.

[2] W. LI, J. KREHL, J.W. GILLESPIE. Process and Performance Evaluation of the

Vacuum-Assisted rocess. Journal of composite materials, 2004, 38:1803-1814.

[3] H. Genlai, S. Zhijie, W. Mingchao, Z. Zuoguang. experimental research on mechanical properties

of basaltfiber and composites. fiber reinforced plastics/composites. 2006(1), p. 24-27.

[4] G. Yantao, J. Xiwen. Research on Molding Process of Basalt Fiber Boat in VARTM Process. fiber

composites. 2009, (2): 32-35.

[5] C. Houyang, L. Wei, L. Yongkang. Study on Permeability of Basalt Fiber Reinforcements in

VARTM. fiber composites. 2007, 24 (2):51-53.

[6] Z. Hongyan, W. Baochang, Z. Dongxing,L. Dihong, C. Yuyong. Effect of void on the interlaminar

shear fatigue of carbon fiber/ epoxy composite laminates. Acta Materiae Compositae Sinica.

Vol.27(6), p. 32-37.

[7] C.H. Park, J. Bréard, A. Saouab, W.I. Lee.Unified saturation and micro-macro voids method in

Liquid Composite Molding. Int J Mater Form (2008) Suppl1:937–940.

22 Materials, Mechanical Engineering and Manufacture

Materials, Mechanical Engineering and Manufacture 10.4028/www.scientific.net/AMM.268-270 Research on VARTM Technology for Fabricating Basalt Fiber/Vinyl Ester Composites 10.4028/www.scientific.net/AMM.268-270.19