This paper discusses proof-of-concept experiments of composite bistable structures
and is preceded by a companion paper about metallic bistable structures. A bistable
structure is characterized by a stress/strain curve with stable branches separated by
unstable branches. We were interested in a particular bistable structure: one that,
once activated, has a second stronger state with the ability to sustain higher
loads. This allows for a better distribution of damage, and in addition the
structure keeps its integrity for a longer time. Positive results on metallic
configurations under tensile loading have prompted us to try and identify
an equivalent composite configuration, able to show directional control of
damage through this material-driven mechanism. Chain-like configurations
with different reinforcements (T-300 carbon fibers, Kevlar®; 49, E-glass and
Dyneema®;), polyurethane foam core and Kevlar stitching were conceived, designed,
fabricated and investigated. Dyneema prototypes turned out to exhibit the
desired bistable behavior as well as higher energy absorption than their
baselines.
