JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 48

design

Carbon composite boom for concrete
pumping truck: a technological challenge
Carbon fibre composite materials with an epoxy
matrix were used to produce the final sections
of an articulated arm for a concrete pumping
truck. The reduced boom weight allowed reducing the tilting moment and, consequently, the
counterweight, with great benefits in terms of
truck size.

manufacturer of construction machinery, and RIBA Composites Srl, a composite manufacturer whose expertise ranges
from the automotive to the aeronautical sectors, have found
an answer to this question developing monolithic booms for
concrete pumping machines.

Development
The project, which won the 2nd prize in the AWK Innovation
category at the Euro Composite Fair last September in Stuttgart, began in 2008, and took about 3 years to reach mass production. Carbon fibre booms are currently produced at a rate
of approximately 100 units a year, covering many truck models
with variable lengths up to more than 100 metres. The application concerns articulated arms mounted on concrete pumps, as
shown in Figure 1 - not the whole arm but the final sections,
three or four segments, depending on the model. Carbon composite is used where the weight saving is more important for
stability reasons.

Andrea Bedeschi, General Manager,
RIBA Composites Srl,
Paolo Maini, Calculation Department Manager,
CIFA SpA

omposite materials, and carbon fibre in particular, are
generally used in applications where weight reduction is
directly connected to performance. It is customary to think
of sport cars with carbon fibre chassis parts or body works,
and this is even more natural in the aeronautic field, where
payload advantages justify some cost increase. The most typical
applications are complex-shaped components made of thin
solid laminates, or thicker parts involving sandwich structures.
Generally, the thickness of a body panel ranges from 1 mm to
2.5 mm, as an order of magnitude. When the required stiffness
involves increasing the thickness over 4 mm, engineers commonly switch to sandwich technology, where the second area
moment is increased by a central low-density core, whose main
function is to remove the noble material from the neutral axis of
the section.
But what happens if you need to carry kilos of concrete, with
fatigue loads induced by pumping pressure and the necessity
to provide for some damage tolerance for impacts and environmental ageing? Two Italian companies, CIFA Srl, a leading

Fig. 1: Concrete pump with deployed arm on site

A virtuous circle
The position of the centre of mass is clearly affected by the
working extension of the articulated arm. The more deployed
the arm, the farther the masses and the higher the tilting risk,
which needs to be prevented by adding a very heavy counterweight on the truck. From the static moment balance, you can
consider that for each kg saved at a distance of 20 metres from
the centre of mass, you can avoid 20 kg of counterweight at 1
metre of distance. This simplified example clearly shows the efficiency of reducing the weight of the last sections in the articu-

48 jec composites magazine / No85 November - December 2013

JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013