Deformation characteristic of the axially fiber reinforced cylindrical rubber subjected to inner pressure

A McKibben actuator consists of an internally pressurized elastic cylindrical tube covered by a shell braided with two families of inextensible fibers woven at equal and opposite angles to the longitudinal axis. Increasing internal pressure causes the actuator to expand radially and, due to the fiber constraint, contract longitudinally. This contraction provides a large force that can be used for robotic actuation. Based on large deformation membrane theory, the actuator is modeled as a fiber-reinforced cylinder with applied inner pressure and axial load. Given the initial shape, material parameters, axial load, and pressure, the analytical model predicts the deformed actuator shape, fiber angle, and fiber and membrane stresses. The analytical results show that for a long and thin actuator the deformed fiber angle approaches 54°44′ at infinite pressure. The actuator elongates and contracts for actuators with initial angles above and below 54°44′ degrees, respectively. For short and thick actuators with initial angles relatively close to 0 deg or 90 deg, however, a fiber angle boundary layer extends to the middle of the actuator, limiting possible extension or contraction. The calculated longitudinal strain and radius change match experimental results to within 5%.

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TEM characterization of reaction zone in a SiC fiber-reinforced titanium alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105758 ◽

1988 ◽

Vol 46 ◽

pp. 738-739

Author(s):

G. Das ◽

R. E. Omlor

Keyword(s):

Titanium Alloys ◽

Reaction Zone ◽

Carbon Layer ◽

Fiber Reinforced ◽

Reaction Products ◽

Sic Fibers ◽

Sic Fiber ◽

The Matrix ◽

Immense Potential

Fiber reinforced titanium alloys hold immense potential for applications in the aerospace industry. However, chemical reaction between the fibers and the titanium alloys at fabrication temperatures leads to the formation of brittle reaction products which limits their development. In the present study, coated SiC fibers have been used to evaluate the effects of surface coating on the reaction zone in the SiC/IMI829 system.IMI829 (Ti-5.5A1-3.5Sn-3.0Zr-0.3Mo-1Nb-0.3Si), a near alpha alloy, in the form of PREP powder (-35 mesh), was used a茸 the matrix. CVD grown AVCO SCS-6 SiC fibers were used as discontinuous reinforcements. These fibers of 142μm diameter contained an overlayer with high Si/C ratio on top of an amorphous carbon layer, the thickness of the coating being ∽ 1μm. SCS-6 fibers, broken into ∽ 2mm lengths, were mixed with IMI829 powder (representing < 0.1vol%) and the mixture was consolidated by HIP'ing at 871°C/0. 28GPa/4h.

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Techniques for preparing the Lolium perenne coleorhiza for scanning electron microscope evaluation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100124239 ◽

1992 ◽

Vol 50 (1) ◽

pp. 766-767

Author(s):

Susan B.G. Debaene ◽

John S. Gardner ◽

Phil S. Allen

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Lolium Perenne ◽

Morphological Study ◽

Root Hairs ◽

Inner Pressure ◽

Water Potentials ◽

Radicle Emergence ◽

Standard Fixation ◽

Scanning Electron

The coleorhiza is a nonvascular sheath that encloses the embryonic radicle in Poaceae, and is generally the first tissue to emerge during germination. Delicate hairlike extensions develop from some coleorhiza cells prior to radicle emergence. Similar to root hairs, coleorhiza hairs are extremely sensitive to desiccation and are damaged by exposure to negative water potentials. The coleorhiza of Lolium perenne is somewhat spherical when first visible, after which a knob forms at a right angle to the caryopsis due to inner pressure from the elongating radicle. This knob increases in length until the radicle finally punctures the coleorhiza. Standard fixation procedures cause severe desiccation of coleorhiza cells and hairs, making morphological study of the coleorhiza difficult. This study was conducted to determine a more successful process for coleorhiza preservation.

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Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154755 ◽

1989 ◽

Vol 47 ◽

pp. 556-557

Author(s):

K.L. More ◽

R.A. Lowden

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Chemical Vapor ◽

Chemical Vapor Infiltration ◽

Frictional Stress ◽

Fiber Reinforced ◽

Pull Out ◽

Carbon Coated ◽

Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

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Effects of high pressure on the crystallization of carbon fiber reinforced polyetheretherketone (CF/PEEK) laminate composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177519 ◽

1990 ◽

Vol 48 (4) ◽

pp. 876-877

Author(s):

Hong-Ming Lin ◽

C. H. Liu ◽

R. F. Lee

Keyword(s):

High Pressure ◽

Carbon Fiber ◽

Sample Surface ◽

High Yield ◽

Fiber Reinforced ◽

Laminate Composites ◽

Peek Composite ◽

Continuous Carbon Fiber ◽

Carbon Fiber Reinforced

Polyetheretherketone (PEEK) is a crystallizable thermoplastic used as composite matrix materials in application which requires high yield stress, high toughness, long term high temperature service, and resistance to solvent and radiation. There have been several reports on the crystallization behavior of neat PEEK and of CF/PEEK composite. Other reports discussed the effects of crystallization on the mechanical properties of PEEK and CF/PEEK composites. However, these reports were all concerned with the crystallization or melting processes at or close to atmospheric pressure. Thus, the effects of high pressure on the crystallization of CF/PEEK will be examined in this study.The continuous carbon fiber reinforced PEEK (CF/PEEK) laminate composite with 68 wt.% of fibers was obtained from Imperial Chemical Industry (ICI). For the high pressure experiments, HIP was used to keep these samples under 1000, 1500 or 2000 atm. Then the samples were slowly cooled from 420 °C to 60 °C in the cooling rate about 1 - 2 degree per minute to induce high pressure crystallization. After the high pressure treatment, the samples were scanned in regular DSC to study the crystallinity and the melting temperature. Following the regular polishing, etching, and gold coating of the sample surface, the scanning electron microscope (SEM) was used to image the microstructure of the crystals. Also the samples about 25mmx5mmx3mm were prepared for the 3-point bending tests.

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