Biological exoskeletons, in particular those with unusually robust and multifunctional properties, hold enormous potential for the development of improved load-bearing and protective engineering materials. Here, we report new materials and mechanical design principles of the iron-plated multilayered structure of the natural armor of Crysomallon squamiferum, a recently discovered gastropod mollusc from the Kairei Indian hydrothermal vent field, which is unlike any other known natural or synthetic engineered armor. We have determined through nanoscale experiments and computational simulations of a predatory attack that the specific combination of different materials, microstructures, interfacial geometries, gradation, and layering are advantageous for penetration resistance, energy dissipation, mitigation of fracture and crack arrest, reduction of back deflections, and resistance to bending and tensile loads. The structure-property-performance relationships described are expected to be of technological interest for a variety of civilian and defense applications.exoskeleton | mollusc | biomechanics | nanomechanics | nanoindentation M any organisms have evolved robust protective exterior structures over millions of years to maximize survivability in their specific environments. Biological exoskeletons or "natural armor" must fulfill various performance requirements such as wear resistance, dissolution prevention, thermal and hydration regulation, and accommodations for feeding, locomotion, and reproduction. Another critical function of these systems is mechanical protection from predators that can induce damage from, for example, penetration, fatigue, drilling, peeling, chipping, hammering, crushing, and kinetic attacks (1). Hence, a diverse array of macroscopic geometries, sizes, and hierarchical, multilayered composite structures exist (2). The shells of gastropod molluscs have long provided key insights into the mechanical performance of biological armor materials. Early on, Wainwright carried out macroscopic mechanical experiments on bivalve shells and formulated important questions on the contributions of different crystal textures to their strength and other functional properties (3). Soon after, Currey and Taylor characterized the properties of numerous mollusc shell microstructures and determined that the inner nacreous layer had superior mechanical properties (4). Subsequently, three decades of investigations ensued on nacre (5-9), leading to the generalized concept of "mechanical property amplification;" i.e., order of magnitude increases in strength and toughness exhibited by biological composites compared to their individual constituent materials beyond simple rule of mixture formulations (10-12). These discoveries engendered numerous efforts to produce nacre-mimetic composite materials that also exhibit mechanical property amplification (12-15). Design, inspired by nature, of engineering materials with robust and multifunctional mechanical properties [i.e., those which sustain a variety of loading condi...

In 2014, NASA, in partnership with Made In Space, Inc., launched the first 3D printer to the International Space Station. Results of the first phase of operations for this mission demonstrated use of the fused filament fabrication (FFF) process for 3D printing in a microgravity environment. Previously published results indicated differences in density and mechanical properties of specimens printed in microgravity and those manufactured with the printer prior to its launch to ISS. Based on extensive analyses, these differences were hypothesized to be a result of subtle changes in manufacturing process settings rather than a microgravity influence on the FFF process. Phase II operations provided an opportunity to produce additional specimens in microgravity, evaluate the impact of changes in the extruder standoff distance, and ultimate provide a more rigorous assessment of microgravity effects through control of manufacturing process settings. Based on phase II results and a holistic consideration of phase I and phase II flight specimens, no engineering-significant microgravity effects on the process are noted. Results of accompanying material modeling efforts, which simulate the FFF process under a variety of conditions (including microgravity), are also presented. No significant microgravity effects on material outcomes are noted in the physics-based model of the FFF process. The 3D printing in zero G technology demonstration mission represents the first instance of off-world manufacturing. It represents the first step toward transforming logistics for long duration space exploration and is also an important crew safety enhancement for extended space missions where cargo resupply is

A sandwich hybridization assay (SHA) was developed to detect 16S rRNAs indicative of phylogenetically distinct groups of marine bacterioplankton in a 96-well plate format as well as low-density arrays printed on a membrane support. The arrays were used in a field-deployable instrument, the Environmental Sample Processor (ESP). The SHA employs a chaotropic buffer for both cell homogenization and hybridization, thus target sequences are captured directly from crude homogenates. Capture probes for seven of nine different bacterioplankton clades examined reacted specifically when challenged with target and non-target 16S rRNAs derived from in vitro transcribed 16S rRNA genes cloned from natural samples. Detection limits were between 0.10-1.98 and 4.43- 12.54 fmole ml(-1) homogenate for the 96-well plate and array SHA respectively. Arrays printed with five of the bacterioplankton-specific capture probes were deployed on the ESP in Monterey Bay, CA, twice in 2006 for a total of 25 days and also utilized in a laboratory time series study. Groups detected included marine alphaproteobacteria, SAR11, marine cyanobacteria, marine group I crenarchaea, and marine group II euryarchaea. To our knowledge this represents the first report of remote in situ DNA probe-based detection of marine bacterioplankton.

Ultrasonic wave methods constitute the leading physical mechanism for nondestructive evaluation (NDE) and structural health monitoring (SHM) of solid composite materials, such as carbon fiber reinforced polymer (CFRP) laminates. Computational models of ultrasonic wave excitation, propagation, and scattering in CFRP composites can be extremely valuable in designing practicable NDE and SHM hardware, software, and methodologies that accomplish the desired accuracy, reliability, efficiency, and coverage. The development and application of ultrasonic simulation approaches for composite materials is an active area of research in the field of NDE. This paper presents comparisons of guided wave simulations for CFRP composites implemented using four different simulation codes: the commercial finite element modeling (FEM) packages ABAQUS, ANSYS, and COMSOL, and a custom code executing the Elastodynamic Finite Integration Technique (EFIT). Benchmark comparisons are made between the simulation tools and both experimental laser Doppler vibrometry data and theoretical dispersion curves. A pristine and a delamination type case (Teflon insert in the experimental specimen) is studied. A summary is given of the accuracy of simulation results and the respective computational performance of the four different simulation tools.