Damage tolerance of bio-inspired helicoidal composites under low velocity impact

Abstract

It is well known that laminated composite materials are prone to impact damage caused by foreign objects and exhibit poor damage resistance in through the thickness direction. By drawing inspiration from naturally occurring impact resistant structures, such as dactyl clubs of mantis shrimp, enhanced damage tolerance and impact energy absorption can be achieved with traditional CFRP layers by creatively arranging them into bio-inspired configurations, called helicoidal or Bouligand structures. Through an extensive numerical analyses of low velocity impact (LVI) supported by the experimental results, a further insight into the possibilities that these structures can offer in terms of damage resistance was attained. By comparing the results of three square plates with different planar sizes, it was shown that the helicoidal layups are more effective at absorbing energy while minimising through the thickness failure than standard quasi-isotropic and cross-ply laminates. Although the helicoidal composites generally exhibited a higher degree of delamination in LVI tests, the standard lamination schemes displayed higher degree of perforation, which resulted in a reduced residual strength in the compression after impact (CAI) testing of a quasi-isotropic laminate compared to several helicoidal ones subjected to 40 J and 80 J impact energy. Furthermore, using advanced finite element analysis (FEA) code LS-DYNA® for simulating LVI and CAI events, it was revealed that the helicoidal arrangement endured the least amount of fibre damage.

Impact resistance of nanocellulose films with bioinspired Bouligand microstructures

“…This optimal range, which features relatively small pitch angles, is remarkably similar to the pitch angles adopted by natural Bouligand structures. 4,29 Previously, experiments with bio-inspired, ber-reinforced composites that contain Bouligand structures have shown that their damage tolerance during impact increases with decreasing g. 14,15 However, this is the rst time that an optimal pitch angle range has been described for the Bouligand structures that maximizes their ballistic performance, which offers guidance for how 1D nanostructures should be arranged layer-by-layer to produce damage tolerant lms.…”

“…13,14 Potential applications of these materials include protective shields for vehicles, body armor, eyewear, packaging, and stretchable and wearable electronics. [14][15][16] While numerous experimental and computational investigations have attempted to explain the structure-property relationships of Bouligand microstructures that give rise to its impact tolerance, no consensus has emerged regarding the dominant deformation mechanisms associated with this microstructure. Bouligand lamellae in sh scales have been shown to reorient towards external tensile loads during mechanical testing using X-ray scattering, leading to enhanced toughness through stretching and sliding mechanisms.…”

“…[18][19][20][21][22][23][24] Experiments and nite element analyses of Bouligand structured composites have demonstrated improved impact resistance and higher residual strength (as much as 80%) compared to quasi-isotropic structures by effectively spreading impact energy in-plane. 14,15,20 Ballistic impact tests have revealed that Bouligand structures ( Fig. 1b) with smaller interply, or pitch (g), angles (22.5 # g # 45 ) lead to higher ballistic limits and can absorb up to 15% more energy during ballistic impacts with larger delamination areas and lower degrees of internal damage.…”

Bioinspired designs for shock absorption, based upon nacre and Bouligand structures

“…The biomimetic models were found to have improved fracture toughness over conventional laminate specimen. Ginzburg et al [20] conducted numerical studies of helicoidal composites subject to Low Velocity Impact (LVI), and found that helicoidal composites had the least amount of fiber damage, post-impact.…”

“…Some of these models were subsequently modified to incorporate related features, from other, suitable geometries such as Bouligand structures [14,20,[31][32][33][34] and biological sutures [25]. Bouligand structures were mimicked by orienting each layer of nacre mimetic aluminum plates at a slightly different angle in the plane of the lamina, while sutures were created as jigsaw interlocks between adjacent tablets in the same plane (L3, L4).…”