It is well known that Rapid Prototyping (RP) and Rapid Tooling (RT) are fundamental technologies to reduce the time tomarket and consequently increase productivity and competitiveness of companies working in different industrial sectors.RT with epoxy resins is presently accepted as an established process of indirect rapid tooling. However, patents,processing difficulties and companies limitations disable a wider implementation of this technology.This paper presents the experimental results of a detailed work, conducted at INEGI, to manufacture moulds for plasticinjection, with tailored properties, using RP models and aluminium filled and fibres reinforced epoxy resins

F. Jorge Lino

Pedro V. Vasconcelos

R. J. Neto

English

Repositório Aberto da Universidade do Porto

INDIRECT RAPID TOOLING WITH ALUMINIUM AND MILLED FIBRE REINFORCED RESINS  F. Jorge Linoa, Pedro V. Vasconcelosb, R. J. Netoc  a FEUP - Faculdade de Engenharia da Universidade do Porto, DEMEGI – Departamento de Engenharia Mecânica e Gestão Industrial, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal b ESTG/ IPVC - Instituto Politécnico de Viana do Castelo, Ap. 574, 4900-908 Viana do Castelo, Portugal cINEGI - Instituto de Engenharia Mecânica e Gestão Industrial, Rua do Barroco, 174-214, 4465-591 Leça do Balio, Porto, Portugal  Abstract  It is well known that Rapid Prototyping (RP) and Rapid Tooling (RT) are fundamental technologies to reduce the time to market and consequently increase productivity and competitiveness of companies working in different industrial sectors. RT with epoxy resins is presently accepted as an established process of indirect rapid tooling. However, patents, processing difficulties and companies’ limitations disable a wider implementation of this technology. This paper presents the experimental results of a detailed work, conducted at INEGI, to manufacture moulds for plastic injection, with tailored properties, using RP models and aluminium filled and fibres reinforced epoxy resins.  Keywords: Rapid Tooling, Injection Moulding, Epoxy Resin Composites, Milled Fibres    1. Introduction  The rapid development and the easy accessibility to CAD programs associated to the Rapid Prototyping (RP) and Rapid Tooling (RT) technologies were fundamental to give a new impulse to the resin tooling. The Design and Product Development departments of companies use RT systems for the production of prototypes moulds in silicone, polyurethane and epoxy resins, just to mention the more commons. These prototype moulds allow the production of dozens to hundreds of parts for visual aids, geometric and dimensional analysis, and frequently thermoplastic functional prototypes. Particularly, for these last prototypes, epoxy based composites are used to manufacture the injection moulds for thermoplastics that can withstand the high pressures and temperatures of the injection cycle. Naturally, the expected life of these moulds lies between 100 and 1000 cycles and is significantly lower than the one obtained with the conventional metallic moulds. As the development of an industrial product rarely demands a number of parts higher than 200, it can be concluded that these technologies are very attractive and well adjusted for this specific application [1-4]. Fig. 1 shows two of these moulds that were used in the production of pre-series of an automatic teller machine and of a latch, respectively.    a)  b) Fig. 1. Epoxy based composite moulds for thermoplastics injection: a) terminal of an automatic teller machine; b) latch. The figure also shows the injected parts. The composite moulds based on high temperature epoxy resins, used in rapid tooling, exhibit an intermediate durability between the soft and the hard tooling. This is due to the combination of the high strength and good thermal stability of the epoxy resin, with the stiffness, hardness and good thermal conductivity of the metallic particles. This last characteristic reduces the thermal shock in the mould in each injection cycle, lowering the mould temperature and the injection cycle time. This work intends to contribute to the implementation of this rapid tooling technology as viable alternative for the production of prototypes and pre series with reduced costs and time-to-market, increasing companies’ competitiveness [5-7].  2. Experimental  The main parameters considered in the selection of the polymeric matrix were:   - Behaviour at high temperature;   - Viscosity and adhesive capacity;   - Low cost. After the epoxy system selection, it is advisable to perform some experiences and tests to improve the mixture formulation and the processing technique and, consequently, the general properties of the composite mould. The components concentrations and the curing cycle should be properly adjusted to optimise the composite properties.   After studying the parameters that control the selection of materials and their processing, and characterize the epoxy-based composites, aluminium filled composites (AF), with different aluminium particles concentrations, and hybrid composites composed by aluminium particles and milled glass fibres (AFG) were produced [8, 9]. Their respective microstructures are presented in Fig. 2, and show grey aluminium round particles and dark elongated glass fibres.  The epoxy matrix system composition is indicated in table 1 [10]. The technical characteristics of the dispersed materials are presented in table 2, while table 3 indicates the composition of the three materials produced. The processing conditions, the dimensional changes occurring during the process, the mechanical and the wear resistance evolution with the temperature, and the thermal conductivity, were studied with detail, with the objective of producing moulds with optimised properties for thermoplastic injection. After being characterized in laboratory, the most promising composites moulds were tested in an industrial thermoplastic injection machine.    a)           100 µm   b) Fig. 2. Epoxy resin composites filled with: a) round aluminium particles (AF); b) aluminium and milled elongated glass fibres (AFG).   Table 1. Epoxy system composition. Epoxy system Araldite LY5210/Aradur HY2954 (Vantico-USA) Epoxy components ● TGDDM = N, N, N´, N´- tetraglycidyl – 4, 4´ - diaminodifenylmethane ● butahedioldiglycidyl ether Curing agent ●2, 2’-dimetil-4,4’-metilenobis (ciclohexilamine)  100 µ m  Table 2. Technical characteristics of the aluminium particles and of the milled glass fibres. Fibre type Manufacturer Dimensions Sizing Aluminium particle (>98.7% aluminium) Hexcel (France) P200 degree - Glass fibres PPG (USA) 215/11 µm (l/d)* Polyvinyl acetate with silane *l/d – fibre length / diameter.  Table 3. Designation and composition of the materials produced. Epoxy resin (A) Aluminium filled composite (AF) Hybrid Composite (AFG) A – 100% A – 59 % F – 41 % A – 57.5 % F – 38.5 % G – 4 % A – Epoxy resin; F - Fine aluminium particles; G – Glass milled fibres  3. Results  3.1 Laboratorial  Considering the specification of the epoxy systems and the particularities of the processing techniques for these types of composite materials, the following conclusions should be highlighted: Long pot-life resins (several hours) allow the use of more complex processing methods, ensuring the reduction of the micro and the macro porosity [11]. Fig. 3 describes the main steps used in this work that assured a very low level of porosity in the composites produced.  (a) (b)(c) (d)  Fig. 3. New resin processing method employed in this work that uses vacuum pouring: a) manual component mixture; b) first degassing; c) second degassing with agitation; d) vacuum pouring.  The gelation process of this resin system, occurring at a higher temperature (40ºC) than the room temperature, promotes a thermal expansion of the model that reduces its dimensional accuracy. This is particularly severe when a silicone model is used, because this material has a higher coefficient of thermal expansion than other types of RP models. - The post-cure at high temperature, necessary to guarantee the complete cure of the composite, leads to higher constraints, tensions and distortions than in less demanding resins.   - The complexity of the curing mechanism of these amino-glycidyl epoxy resins demands a high temperature and long thermal cycles to ensure their complete cure [12-14], representing a disadvantage in Rapid Tooling applications (more difficulties in controlling dimensions and distortions of the tools). Flexural tests show that aluminium particles addition improves significantly the elastic modulus. The addition of milled fibres to these composites contributes to a small increase on the flexural strength, as one can see in the graph of Fig. 4.  0 20 40 60 80AAFAFGFlexural strength (MPa) Elastic Modulus (GPa)Fig. 4. Flexural strength and elastic modulus of the A, AF and AFG materials.  Fig. 5 presents the dynamic mechanical thermal analysis (DMTA) results, showing that the addition of metallic particles improves the material stiffness, at both room temperature and high temperatures (more pronounced below 200ºC). At 200º C the elastic modulus is abruptly reduced due to the glass transition temperature. The graph only presents AF curve because AFG exhibits a similar behaviour.  0100020003000400050000 50 100 150 200 250 300Temperature (ºC)Elastic modulus (MPa)A AF Fig. 5. Elastic modulus as a function of temperature, for the neat resin (A) and aluminium filled epoxy (AF), obtained in DMTA tests.  The incorporation of high aluminium particles concentrations allows a significant reduction on the coefficient of thermal expansion (CTE) (Fig. 6), which is very important for controlling the dimensional variations occurring from the initial prototype to the final mould. These aluminium particles have also the advantage of increasing the thermal conductivity of the composite, relatively to the epoxy matrix, by about an order of magnitude. This is a very important factor because it reduces the injection cycle of the mould. The milled glass fibres, although well mixed in the AFG composite, have a small negative effect on the thermal conductivity, as one can see in Fig. 7.  0 2 4 6 8AAFAFGCoefficient of thermal expansion (CTE) x10-5 Fig. 6. AF and AFG composites exhibit lower CTE than the A epoxy resin.  Fig. 8 shows the specific wear rate results for the A, AF and AFG materials, at room temperature and at 160ºC, determined in a reciprocating tribometer. Details of this test can be obtained in reference [15]. The AFG hybrid composite exhibits a significantly better wear behaviour than the conventional AF composite. As expected, the temperature increase enhances considerably the wear rate, with drastic values for the AF composite.  0 0.5 1 1.5 2 2.5AAFAFGThermal conductivity (W.m-1.C-1) Fig. 7. Thermal conductivity of the three tested materials.  020406080100A AF AFGWs-Wear rate (10-5 mm3 /Nm)RT 160ºC Fig. 8. Specific wear rate of epoxy (A), epoxy with aluminium (AF) and epoxy with aluminium and fibres (AFG) systems at room temperature and at 160ºC, determined in the reciprocating tribometer.  3.2 Industrial environment  AF and AFG moulds of a latch were placed in an industrial machine and polyacetal parts were injected in them. The moulds wear was measured by an indirect approach, through the determination of the dimensional differences measured in the injected parts, spaced by 50 parts in the injection cycles. The six dimensions that were controlled in each part are indicated in Fig. 9. The results obtained are presented in Table 4. After 50 injection cycles, AF mould reveals a small wear, while in the AFG mould no significant wear was detected (accuracy: 0.01 mm). The mould surface finishing was also analysed, after 90 injection cycles. The initial medium roughness of both moulds was 0.85µm and, after 90 injections, it was 1.41µm for the AF mould and only 0.94µm for the AFG mould (Tab. 5). These results also confirm that the AFG composite mould presents better physical integrity and erosive wear resistance than the AF composite, which is in accordance with the laboratorial results.   Fig. 9. Latch model dimensions used in the geometric control.  Table 4. Results of the dimensional control of the injected parts in the AF and AFG moulds, spaced by 50 injection cycles. Dimensions Reference A B C D E F AF difference (mm) 0.02 0.10 0.03 0.03 0.05 0.03 AFG difference (mm) 0 0 0 0 0 0.01  Table 5. Surface roughness of the studied moulds, after 90 injection cycles. Mould Roughness criteria, (µm)  Ra Rz Rmáx AF  1.41 11.37 13.83 AFG 0.94 6.84 7.96  SEM images of the two composites moulds surfaces (Fig. 10) also reveal a deeper excoriation in AF moulds, confirming the quantitative results.   a)  b) Fig. 10. SEM images of the moulding surfaces, revealing the degree of excoriation in the thermoplastic flow direction of the: a) AF and; b) AFG moulds. This mould shows a smoother surface.  4. Conclusions  Epoxy resin composites are suited for rapid tooling applications if adequate processing conditions and tailored concentrations of the different composite components are applied. In this paper it was shown that: - The thermal conductivity of the composites is related with the capacity of metallic loading allowed by the epoxy system. High metallic concentrations (40%) reduce the injection cycles and the thermal shock and increase the mould life. The addition of the metallic particles also improves the elastic modulus at low and high temperature and reduces the CTE; - Milled glass fibres, when added in small concentrations (4 %) to the epoxy aluminium filled composites improve substantially the composite abrasive and erosive wear resistance and consequently turn this type of composites particularly indicated for rapid tooling applications.  Acknowledgements  Financial support from FEDER through the project POCTI/EME/41199/2001, “Development of an Indirect Rapid Tooling Process Based in Polymeric Matrix Composites”, approved by the Fundação para a Ciência e Tecnologia (FCT) and POCTI. Partly funded by European Social Fund, public contest 4/5.3/PRODEP/2000, submitted by Escola Superior de Tecnologia e Gestão of Instituto Politécnico de Viana do Castelo.  References  [1] P. Vasconcelos, F. Jorge Lino, R. J. Neto. Advanced Materials Forum, 1st International Material Symposium, Coimbra, Portugal, Key Engineering Materials, Ed. by T. Vieira, Vol. 230-232, 169-172, 2002.  [2] P. Vasconcelos, F. Jorge Lino, R. J. Neto, O Fabrico Rápido de Ferramentas ao Serviço da Engenharia Concorrente, Tecnometal, 136, 17-21, 2001.   [3] F. Jorge Lino, F. Braga, M. Simão, R. J. Neto, T. P. Duarte, Protoclick – Prototipagem Rápida, Ed. by Protoclick, Porto, Portugal, 2001.  [4] C. K. Chua, K. F. Leong, C. S. Lim, Rapid Manufacturing: Principles and Applications, World Scientific Publishing Co. Pte Ltd., 2003.  [5] S. K. Bhattacharya, Metal-Filled Polymers, Marcel Dekker Inc., USA, 1986.   [6] U. Baraldi, C. Emmerchts, Low Cost Tooling for Injection Moulding, Proceedings of Composites Tooling III, Elsevier Science Ltd., 27-42, 1994.  [7] P. Vasconcelos, F. Jorge Lino, R. J. Neto, Fabrico Rápido de Ferramentas Utilizando Resinas Carregadas, Proceedings of 1as Jornadas Politécnicas de Engenharia Mecânica, Leiria, Portugal, 2001.  [8] P. Vasconcelos, F. Jorge Lino, R. J. Neto, P. Henrique, Advanced Materials Forum, Contribution of the Phase-Matrix Interface in the Behaviour of Aluminium Filled Epoxies, 1st International Material Symposium, Coimbra, Portugal, Key Engineering Materials, Ed. by T. Vieira, Vol. 230-232, 635-638, 2004.  [9] P. Vasconcelos, F. Jorge Lino, F.V. Hattum, R. J. Neto, Advanced Materials Forum, Mathematical Models for Particulate Filled and Milled Fibre Reinforced Composites, 1st International Material Symposium, Coimbra, Portugal, Key Engineering Materials, Ed. by T. Vieira, Vol. 230-232, 742-745, 2004.  [10] Vantico Ltd Publicity, Data Sheet, Matrix Systems for Aerospace Composites, 2001.   [11] P. Vasconcelos, F. Jorge Lino, R. J. Neto, Importance of the Vacuum in Rapid Tooling of Polymeric-Based Moulds, RPD 2004 – Rapid Product Development, Centimfe, Marinha Grande, Portugal, October 2004.   [12] L. Matejka, K. Dusek, Mechanism and Kinetics of Curing Epoxides Based on Diglycidylamine with Aromatic Amines. 1. The Reaction of Diglycidylaniline with Secondary Amines, Macromolecules 22, 2902 – 2911, 1989.  [13] L. Matejka, Amine Cured Epoxide Networks: Formation, Structure and Properties, Macromolecules 33, 3611 – 3619, 2000.   [14] B. A. Rozenberg, Kinetics, Thermodynamics and Mechanism of Reactions of Epoxy Oligomers with Amines, Adv. Polym. Sci., 75, 113-165, 1986.  [15] P. Vasconcelos, F. J. Lino, A. M. Baptista, R. Neto, Tribological Behaviour of Epoxy Based Composites for Rapid Tooling, accepted for publication in J. Wear, December (2004).   

Indirect rapid tooling with aluminium and milled fibre reinforced resins

Open Repository of the University of Porto

INDIRECT RAPID TOOLING WITH ALUMINIUM AND MILLED FIBRE 
REINFORCED RESINS 
 
F. Jorge Linoa, Pedro V. Vasconcelosb, R. J. Netoc 
 
a FEUP - Faculdade de Engenharia da Universidade do Porto, DEMEGI – Departamento de Engenharia Mecânica e Gestão 
Industrial, Rua Dr. Roberto Frias, 4200-465 Porto, 
Portugal 
b
 ESTG/ IPVC - Instituto Politécnico de Viana do Castelo, Ap. 574, 4900-908 Viana do 
Castelo, Portugal 
cINEGI - Instituto de Engenharia Mecânica e Gestão Industrial, Rua do Barroco, 174-214, 4465-591 Leça do Balio, 
Porto, Portugal 
 
Abstract 
 
It is well known that Rapid Prototyping (RP) and Rapid Tooling (RT) are fundamental technologies to reduce the time to 
market and consequently increase productivity and competitiveness of companies working in different industrial sectors. 
RT with epoxy resins is presently accepted as an established process of indirect rapid tooling. However, patents, 
processing difficulties and companies’ limitations disable a wider implementation of this technology. 
This paper presents the experimental results of a detailed work, conducted at INEGI, to manufacture moulds for plastic 
injection, with tailored properties, using RP models and aluminium filled and fibres reinforced epoxy resins. 
 
Keywords: Rapid Tooling, Injection Moulding, Epoxy Resin Composites, Milled Fibres 
 
 
 
1. Introduction 
 
The rapid development and the easy accessibility 
to CAD programs associated to the Rapid Prototyping 
(RP) and Rapid Tooling (RT) technologies were 
fundamental to give a new impulse to the resin 
tooling. The Design and Product Development 
departments of companies use RT systems for the 
production of prototypes moulds in silicone, 
polyurethane and epoxy resins, just to mention the 
more commons. These prototype moulds allow the 
production of dozens to hundreds of parts for visual 
aids, geometric and dimensional analysis, and 
frequently thermoplastic functional prototypes. 
Particularly, for these last prototypes, epoxy based 
composites are used to manufacture the injection 
moulds for thermoplastics that can withstand the high 
pressures and temperatures of the injection cycle. 
Naturally, the expected life of these moulds lies 
between 100 and 1000 cycles and is significantly 
lower than the one obtained with the conventional 
metallic moulds. As the development of an industrial 
product rarely demands a number of parts higher than 
200, it can be concluded that these technologies are 
very attractive and well adjusted for this specific 
application [1-4]. Fig. 1 shows two of these moulds 
that were used in the production of pre-series of an 
automatic teller machine and of a latch, respectively.  
 
 
a) 
 
b) 
Fig. 1. Epoxy based composite moulds for thermoplastics 
injection: a) terminal of an automatic teller machine; b) 
latch. The figure also shows the injected parts. 
The composite moulds based on high temperature 
epoxy resins, used in rapid tooling, exhibit an 
intermediate durability between the soft and the hard 
tooling. This is due to the combination of the high 
strength and good thermal stability of the epoxy resin, 
with the stiffness, hardness and good thermal 
conductivity of the metallic particles. This last 
characteristic reduces the thermal shock in the mould 
in each injection cycle, lowering the mould 
temperature and the injection cycle time. This work 
intends to contribute to the implementation of this 
rapid tooling technology as viable alternative for the 
production of prototypes and pre series with reduced 
costs and time-to-market, increasing companies’ 
competitiveness [5-7]. 
 
2. Experimental 
 
The main parameters considered in the selection of 
the polymeric matrix were:   
- Behaviour at high temperature;   
- Viscosity and adhesive capacity;   
- Low cost. 
After the epoxy system selection, it is advisable to 
perform some experiences and tests to improve the 
mixture formulation and the processing technique and, 
consequently, the general properties of the composite 
mould. The components concentrations and the curing 
cycle should be properly adjusted to optimise the 
composite properties.   
After studying the parameters that control the 
selection of materials and their processing, and 
characterize the epoxy-based composites, aluminium 
filled composites (AF), with different aluminium 
particles concentrations, and hybrid composites 
composed by aluminium particles and milled glass 
fibres (AFG) were produced [8, 9]. Their respective 
microstructures are presented in Fig. 2, and show grey 
aluminium round particles and dark elongated glass 
fibres.  
The epoxy matrix system composition is indicated 
in table 1 [10]. The technical characteristics of the 
dispersed materials are presented in table 2, while 
table 3 indicates the composition of the three materials 
produced. 
The processing conditions, the dimensional 
changes occurring during the process, the mechanical 
and the wear resistance evolution with the 
temperature, and the thermal conductivity, were 
studied with detail, with the objective of producing 
moulds with optimised properties for thermoplastic 
injection. 
After being characterized in laboratory, the most 
promising composites moulds were tested in an 
industrial thermoplastic injection machine. 
 
 
 
a) 
 
 
    
    100 µm  
 
b) 
Fig. 2. Epoxy resin composites filled with: a) round 
aluminium particles (AF); b) aluminium and milled 
elongated glass fibres (AFG). 
 
 
Table 1. Epoxy system composition. 
Epoxy system Araldite LY5210/Aradur HY2954 (Vantico-USA) 
Epoxy components ● TGDDM = N, N, N´, N´- tetraglycidyl – 4, 4´ 
- diaminodifenylmethane ● butahedioldiglycidyl ether 
Curing agent ●2, 2’-dimetil-4,4’-metilenobis (ciclohexilamine) 
 
100 µ m 
 Table 2. Technical characteristics of the aluminium particles and of the milled glass fibres. 
Fibre type Manufacturer Dimensions Sizing 
Aluminium particle 
(>98.7% aluminium) 
Hexcel (France) P200 degree - 
Glass fibres PPG (USA) 215/11 µm (l/d)* Polyvinyl acetate with silane 
*l/d – fibre length / diameter. 
 
Table 3. Designation and composition of the materials 
produced. 
Epoxy 
resin 
(A) 
Aluminium 
filled composite 
(AF) 
Hybrid 
Composite 
(AFG) 
A – 100% A – 59 % 
F – 41 % 
A – 57.5 % 
F – 38.5 % 
G – 4 % 
A – Epoxy resin; F - Fine aluminium particles; 
G – Glass milled fibres 
 
3. Results 
 
3.1 Laboratorial 
 
Considering the specification of the epoxy systems 
and the particularities of the processing techniques for 
these types of composite materials, the following 
conclusions should be highlighted: 
Long pot-life resins (several hours) allow the use 
of more complex processing methods, ensuring the 
reduction of the micro and the macro porosity [11]. 
Fig. 3 describes the main steps used in this work that 
assured a very low level of porosity in the composites 
produced. 
 
(a) (b)
(c) (d)
 
 
Fig. 3. New resin processing method employed in this work 
that uses vacuum pouring: a) manual component mixture; 
b) first degassing; c) second degassing with agitation; d) 
vacuum pouring. 
 
The gelation process of this resin system, occurring 
at a higher temperature (40ºC) than the room 
temperature, promotes a thermal expansion of the 
model that reduces its dimensional accuracy. This is 
particularly severe when a silicone model is used, 
because this material has a higher coefficient of 
thermal expansion than other types of RP models. 
- The post-cure at high temperature, necessary to 
guarantee the complete cure of the composite, leads to 
higher constraints, tensions and distortions than in less 
demanding resins.   
- The complexity of the curing mechanism of these 
amino-glycidyl epoxy resins demands a high 
temperature and long thermal cycles to ensure their 
complete cure [12-14], representing a disadvantage in 
Rapid Tooling applications (more difficulties in 
controlling dimensions and distortions of the tools). 
Flexural tests show that aluminium particles 
addition improves significantly the elastic modulus. 
The addition of milled fibres to these composites 
contributes to a small increase on the flexural 
strength, as one can see in the graph of Fig. 4. 
 
0 20 40 60 80
A
AF
AFG
Flexural strength (MPa) Elastic Modulus (GPa)
Fig. 4. Flexural strength and elastic modulus of the A, AF 
and AFG materials. 
 
Fig. 5 presents the dynamic mechanical thermal 
analysis (DMTA) results, showing that the addition of 
metallic particles improves the material stiffness, at 
both room temperature and high temperatures (more 
pronounced below 200ºC). At 200º C the elastic 
modulus is abruptly reduced due to the glass transition 
temperature. The graph only presents AF curve 
because AFG exhibits a similar behaviour. 
 
0
1000
2000
3000
4000
5000
0 50 100 150 200 250 300
Temperature (ºC)
El
a
st
ic
 
m
o
du
lu
s 
(M
Pa
)
A AF
 
Fig. 5. Elastic modulus as a function of temperature, for the 
neat resin (A) and aluminium filled epoxy (AF), obtained in 
DMTA tests. 
 
The incorporation of high aluminium particles 
concentrations allows a significant reduction on the 
coefficient of thermal expansion (CTE) (Fig. 6), 
which is very important for controlling the 
dimensional variations occurring from the initial 
prototype to the final mould. These aluminium 
particles have also the advantage of increasing the 
thermal conductivity of the composite, relatively to 
the epoxy matrix, by about an order of magnitude. 
This is a very important factor because it reduces the 
injection cycle of the mould. The milled glass fibres, 
although well mixed in the AFG composite, have a 
small negative effect on the thermal conductivity, as 
one can see in Fig. 7. 
 
0 2 4 6 8
A
AF
AFG
Coefficient of thermal expansion (CTE) x10-5
 
Fig. 6. AF and AFG composites exhibit lower CTE than the 
A epoxy resin. 
 
Fig. 8 shows the specific wear rate results for the 
A, AF and AFG materials, at room temperature and at 
160ºC, determined in a reciprocating tribometer. 
Details of this test can be obtained in reference [15]. 
The AFG hybrid composite exhibits a significantly 
better wear behaviour than the conventional AF 
composite. As expected, the temperature increase 
enhances considerably the wear rate, with drastic 
values for the AF composite. 
 
0 0.5 1 1.5 2 2.5
A
AF
AFG
Thermal conductivity (W.m-1.C-1)
 
Fig. 7. Thermal conductivity of the three tested materials. 
 
0
20
40
60
80
100
A AF AFGW
s-
W
ea
r 
ra
te
 
(10
-
5 m
m
3 /N
m
)
RT 160ºC
 
Fig. 8. Specific wear rate of epoxy (A), epoxy with 
aluminium (AF) and epoxy with aluminium and fibres 
(AFG) systems at room temperature and at 160ºC, 
determined in the reciprocating tribometer. 
 
3.2 Industrial environment 
 
AF and AFG moulds of a latch were placed in an 
industrial machine and polyacetal parts were injected 
in them. The moulds wear was measured by an 
indirect approach, through the determination of the 
dimensional differences measured in the injected 
parts, spaced by 50 parts in the injection cycles. The 
six dimensions that were controlled in each part are 
indicated in Fig. 9. The results obtained are presented 
in Table 4. 
After 50 injection cycles, AF mould reveals a 
small wear, while in the AFG mould no significant 
wear was detected (accuracy: 0.01 mm). 
The mould surface finishing was also analysed, 
after 90 injection cycles. The initial medium 
roughness of both moulds was 0.85µm and, after 90 
injections, it was 1.41µm for the AF mould and only 
0.94µm for the AFG mould (Tab. 5). These results 
also confirm that the AFG composite mould presents 
better physical integrity and erosive wear resistance 
than the AF composite, which is in accordance with 
the laboratorial results. 
 
 
Fig. 9. Latch model dimensions used in the geometric 
control. 
 
Table 4. Results of the dimensional control of the injected 
parts in the AF and AFG moulds, spaced by 50 injection 
cycles. 
Dimensions 
Reference 
A B C D E F 
AF difference 
(mm) 
0.02 0.10 0.03 0.03 0.05 0.03 
AFG difference 
(mm) 
0 0 0 0 0 0.01 
 
Table 5. Surface roughness of the studied moulds, after 90 
injection cycles. 
Mould Roughness criteria, (µm) 
 Ra Rz Rmáx 
AF  1.41 11.37 13.83 
AFG 0.94 6.84 7.96 
 
SEM images of the two composites moulds 
surfaces (Fig. 10) also reveal a deeper excoriation in 
AF moulds, confirming the quantitative results. 
 
 
a) 
 
b) 
Fig. 10. SEM images of the moulding surfaces, revealing 
the degree of excoriation in the thermoplastic flow direction 
of the: a) AF and; b) AFG moulds. This mould shows a 
smoother surface. 
 
4. Conclusions 
 
Epoxy resin composites are suited for rapid tooling 
applications if adequate processing conditions and 
tailored concentrations of the different composite 
components are applied. 
In this paper it was shown that: 
- The thermal conductivity of the composites is 
related with the capacity of metallic loading allowed 
by the epoxy system. High metallic concentrations 
(40%) reduce the injection cycles and the thermal 
shock and increase the mould life. The addition of the 
metallic particles also improves the elastic modulus at 
low and high temperature and reduces the CTE; 
- Milled glass fibres, when added in small 
concentrations (4 %) to the epoxy aluminium filled 
composites improve substantially the composite 
abrasive and erosive wear resistance and consequently 
turn this type of composites particularly indicated for 
rapid tooling applications. 
 
Acknowledgements 
 
Financial support from FEDER through the project 
POCTI/EME/41199/2001, “Development of an 
Indirect Rapid Tooling Process Based in Polymeric 
Matrix Composites”, approved by the Fundação para a 
Ciência e Tecnologia (FCT) and POCTI. 
Partly funded by European Social Fund, public 
contest 4/5.3/PRODEP/2000, submitted by Escola 
Superior de Tecnologia e Gestão of Instituto 
Politécnico de Viana do Castelo. 
 
References 
 
[1] P. Vasconcelos, F. Jorge Lino, R. J. Neto. Advanced 
Materials Forum, 1st International Material 
Symposium, Coimbra, Portugal, Key Engineering 
Materials, Ed. by T. Vieira, Vol. 230-232, 169-172, 
2002. 
 
[2] P. Vasconcelos, F. Jorge Lino, R. J. Neto, O Fabrico 
Rápido de Ferramentas ao Serviço da Engenharia 
Concorrente, Tecnometal, 136, 17-21, 2001. 
 
 
[3] F. Jorge Lino, F. Braga, M. Simão, R. J. Neto, T. P. 
Duarte, Protoclick – Prototipagem Rápida, Ed. by 
Protoclick, Porto, Portugal, 2001. 
 
[4] C. K. Chua, K. F. Leong, C. S. Lim, Rapid 
Manufacturing: Principles and Applications, World 
Scientific Publishing Co. Pte Ltd., 2003. 
 
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Indirect rapid tooling with aluminium and milled fibre reinforced resins

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