JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 55

More information
Aimplas is a Centre for Innovation and Technology (CIT) recognized by the Spanish Interministerial Committee of Science and Technology. Located in Valencia, Spain, it was founded
in 1990 as a national and international non-profit research association. Since then, it has
focused on developing direct contact with companies in all plastics-related sectors to identify their needs and provide appropriate solutions.
Aimplas offers its clients and partners a highly qualified technical team that specializes in
fields like packaging, construction, automotive, recycling, agriculture, electrical/electronics
and aeronautics. Aimplas provides customized solutions for businesses, R&D project coordination and execution, testing and analysis, technical assistance, competitive intelligence and
training.

different results. This is probably the
reason why reinforcement manufacturers do not include permeability in
the technical data sheets of their products. Therefore, simulation results
depend on the permeability bench
used to measure the permeability
of the different preforms employed
to produce the composite part. The
situation is even worse when vacuumassisted processes are being simulated.
The flow of resin through the thickness of the preform is not negligible,
so that additional characterization
is needed [3]. In this case, it is also
necessary to understand how the resin
flows, both in-plane and between the
different layers.
To conclude, developing a virtual prototype to optimize vacuum-assisted
RTM processes requires considerable
effort in order to characterize the
raw materials. It also requires skilled
personnel to integrate the entire
system (i.e. the flow properties of raw
materials, the design of the part to be
manufactured, and resin flow simulation) and to draw the right conclusions from the results obtained. It
might not always be justified to favour
such efforts over the traditional trial
and error approach.

Fig. 1: Flexible permeability bench at AIMPLAS

New methodology
To reduce the amount of work required to set up a virtual prototype
for VARTM and infusion processes,
Aimplas developed a methodology,
along with an original permeability
bench (Fig. 1) that also includes the
effect of variable preform porosity
due to impregnation and the varying
pressure gradient.
This new methodology considerably
reduces the number of tests needed
to obtain the in-plane and throughthickness permeability data that allows fully characterizing the preforms'
permeability. It also requires less
computation than these processes
usually entail. The Aimplas permeability bench reduces the total cost
of developing the virtual prototype
and, therefore, also lowers the process
optimization costs.
Aimplas tested the concept of flexible
permeability in the development of
several virtual prototypes, characterizing preforms made of glass or natural
fibre, with or without high-permeability cores, etc. The virtual prototypes
were developed with the PAM-RTM®
software and pilot plant comparisons
were carried out (Fig. 2).

Fig. 2: Validation of the virtual prototype at pilot
plant level

As a result of the validation at pilot
plant level, it can be concluded that
the methodology developed by
Aimplas to optimize VARTM processes based on flexible permeability
yields a number of benefits: feasible
results, lower implementation costs,
shorter cycle times and guaranteed
full impregnation of the preform,
which all lower the cost of the finished composite part. n
More information:
www.aimplas.es
References:
[1] Composites Market Report. The European GRP market. Dr Elmar Witten,
AVK, 2012
[2] E. Ruiz et al. Experimental determination of the permeability of
textiles: A benchmark exercise. Composites Part A: Applied Science and
Manufacturing, Volume 42, Issue 9,
September 2011, pages 1157-1168
[3] E. Díaz, C. Sanz, J.A. García, Validation of flexible permeability characterization methods in numerical simulation of infusion processes. Proceeding
of the 10th International Conference
on Flow Processes in Composites
Materials, Ascona, 2010

No84 October 2013

/ jec composites magazine 55

http://www.aimplas.es

JEC COMPOSITES MAGAZINE - Issue #84 - October 2013

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #84 - October 2013