Tech Briefs

Measuring Impact Damage to Toughened CFRP Laminates with Time Domain Reflectometry

Laminated Carbon Fiber Reinforced Polymer (CFRP) composites are very effective in weight saving in aeronautical structural components. For these laminated CFRP structures, it is difficult to detect damage such as delamination, matrix cracks, and local fiber breakages caused by low-velocity impact loading because these damages are difficult to detect from the outside of the structure. This difficulty of inspection of the laminated CFRP structures demands the development of automatic monitoring or damage detection systems.

Posted in: Briefs, Physical Sciences, Measurements, Composite materials, Lightweight materials

Testing Mechanical Properties of Polymer-Based Multi- Phase Particulate Composites

Polymer composites comprised of metallic particles distributed throughout a contiguous polymer matrix can often be modified to produce advanced composites that exhibit multifunctional characteristics. The properties of the particulate composites often depend on varying particle size, loading fractions, particle type, and the adhesion between the particulate and the matrix. Studies have shown that particle size, shape, and concentration, and properties of the constituents can affect mechanical properties. This work compared aluminum and nickel particles in PMMA thermoplastic prepared by injection molding, with the same particles in epoxy prepared in a cast-cure process.

Posted in: Briefs, Physical Sciences, Composite materials, Test procedures

Humanlike Articulated Robotic Headform for Respirator Fit Testing

The testing of individual respiratory protection (IRP) devices is now accomplished with panels of human wearers. Historical at tempts to simulate the human face and head have been unsuccessful for a variety of reasons that include imprecision in reproduction of facial dimensions and unrepresentative textures of the surfaces applied to headforms.

Posted in: Briefs, Physical Sciences, Human factors, Medical equipment and supplies, Robotics

Three-Dimensional Plastic Part Extrusion and Conductive Ink Printing for Flexible Electronics

Structural electronics, or structronics, seeks to build wiring and electrical interconnects directly into component structures to diminish the need for structural fasteners. A MakerBot Cupcake Computer Numerical Control (CNC) was used to investigate the fabrication of plastic structures by printing, and a Fujifilm Dimatix Materials Printer (DMP) was used to create flexible Printed Circuit Boards (PCBs). After developing processes to make these machines easier to use, others will be able to utilize them to develop structures with integrated electronics.

Posted in: Briefs, Manufacturing & Prototyping, Electronic equipment, Additive manufacturing, Plastics, Parts

Micro-Composite Fabrication via Field-Aided Laminar Composite Processing

Much work has been accomplished since the discovery that particles in a dielectric fluid experience forces when placed in an electric field, including mathematical descriptions of the forces and resulting motion of particles of differing shapes, particle separation and segregation for use in drug delivery, and even the manipulation of long-chain molecules of certain polymers.

Posted in: Briefs, Manufacturing & Prototyping, Fabrication, Composite materials, Polymers

Tin-Based IV-IV Heterostructures Fabricated Using Molecular Beam Epitaxy

The indirect nature of the fundamental energy gap in the elemental semiconductors Si and Ge prevents the use of these materials and their alloys in laser devices. The objective of this work is to fabricate Sn-based IV-IV compounds for finding direct bandgap material. This work focuses on the material system GeSn/Ge, from the growth, characterization, and optical measurement. Experimental evidences on pseudomorphic growth of thick Ge1-xSnx film for Sn composition up to 10% and the direct optical transition are presented.

Posted in: Briefs, Manufacturing & Prototyping, Lasers, Fabrication, Alloys, Semiconductors

Stencil Mask Methodology for Parallelized Production of Microscale Mechanical Test Samples

Over the past decade, there has been considerable progress in the development of new mechanical testing methods to characterize the properties of materials at the micro and nano scales. One common application of these testing methodologies is the measurement of mechanical properties of structures that are physically small in scale, such as the strength of nanowhiskers and MEMS devices. Another common application is the use of small sample testing to gain insight into plastic deformation processes through systematic alteration of the sample dimensions in order to help isolate selected aspects of material behavior. Examples of these studies include the exploration of size-scale strengthening effects, the quantitative measurement and analysis of dislocation avalanches, and the measurement of local property variations in engineering alloys.

Posted in: Briefs, Manufacturing & Prototyping, Materials properties, Nanotechnology, Test procedures