smart technologies for safety engineering

Adaptive Impact Absorption 155
Finally, note that the impact load, even if adaptively received, causes some structural vibrations,
which can be damped semi-actively with the use of structural fuses, controlled by the so-called
‘pre-stress accumulation release’ (PAR) strategy (cf. Chapter 7).
5.2 Multifolding Materials and Structures
5.2.1 Introduction
Motivation for the undertaken research comes from responding to increasing requirements for
high-impact energy absorption in the structures exposed to the risk of extreme blast, tall and
compliant offshore structures, etc. Requirements for optimal energy absorbing systems may
be stated as follows:
The system must dissipate the kinetic energy of an impact in a stable and controlled way.
Displacements must not exceed the maximal allowable values.
Extreme accelerations and forces of the impact should be reduced to the lowest possible
level.
The majority of properly designed, passive energy-absorbing systems fulfill the first two of
these requirements. The third one, because of the constant constitutive force–displacement
relation, in this case can be realized only to some extent. Therefore, commonly applied passive
protective systems are optimal for a limited range of loads.
In contrast to the standard solutions, the proposed approach focuses on active adaptation of
energy-absorbing structures (equipped with a sensor system that can detect impact in advance
and controllable semi-active dissipators – structural fuses) with a high ability of adaptation to
extreme overloading.
The idea of multifolding microstructures (MFM) and numerical tools for analysis and optimization
were discussed in detail in References [1] and [2]. The following section will focus
on the most important features and results of experimental verification of the concept.
The proposed MFMs are honeycomb-like structures composed of truss elements equipped
with special devices (so-called ‘structural fuses’) providing control over the force characteristics.
A typical layout of the MFM is depicted in Figure 5.2. The size of the MFM can be
reduced to one or two dimensions (the single-column structure, cf. Figure 5.4).
Figure 5.2 MFM structure