Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.13, #5)
Cracking Models; Broken Parts by Peter W. R. Beaumont (pp. 265-285).
In critical conditions of stress-state, fatigue, or hostile environment, where the objective is to design components and structures for longevity, durability, integrity, and reliability, then the balance between empirical engineering design and physical modelling based on mechanisms of deformation and fracture in the material under attack is shifted in favour of physical modelling. Physical modelling provides the means to assess the relative severity of different loading regimes, as well as load/environment interactions. Furthermore, the physical model points to something of the greatest value; it suggests the proper form that constitutive equations should take in the design process. When combined with experimental evidence, physical modelling has the economic advantage of reducing the high cost of vast experimental programmes of duration of many thousands of hours. Existing design methodologies at the higher structural size scales can be supported and justified by fundamental understanding at lower size scales through the physical model. A word of caution: physical modelling has to be underpinned by the actual mechanisms of failure best observed by direct means such as in situ scanning electron microscopy.
Keywords: multi-scale modelling; physical modelling; failure mechanisms; cracking; fracture; in situ scanning electron microscopy
Mode III Interlaminar Fracture Behavior of Glass Fiber Reinforced Polymer Woven Laminates at 293 to 4 K by Victor Rizov; Yasuhide Shindo; Katsumi Horiguchi; Fumio Narita (pp. 287-304).
This paper deals with mode III delamination properties of glass fiber reinforced polymer woven laminates at room temperature (293 K), liquid nitrogen temperature (77 K), gas helium temperature (20 K), and liquid helium temperature (4 K). In order to evaluate these properties, the Split Cantilever Beam (SCB) fracture test is performed. The load is applied to a test specimen through a set of identical grips in order to reduce (in some degree) the mode II loading at the free edges. A three-dimensional finite element analysis is used to study the stress and strain state of the specimens and to interpret the experimental measurements. The strain energy release rate is calculated by using the virtual crack closure technique. It is found that the strain energy release rate is dominated by the mode III component. A non-uniform distribution of the strain energy release rate along the delamination front is obtained with mode III component having maximum at the center of the delamination front, while mode II component increases towards the free edges. The strain energy release rate is also determined using the crack closure technique. A finite element analysis is also carried out to calculate the stress intensity factors for the SCB specimens. The fracture surfaces are examined by scanning electron microscopy to identify the fracture mechanisms. The most important conclusion from the present study is that at temperature lowering from 293 to 20 K the mode III fracture toughness increases, further cooling to 4 K produces a toughness decrease.
Keywords: composite laminates; cryogenic temperatures; finite element analysis; mode III delamination; strain energy release rate; stress intensity factors
Reduction of Noise from Disc Brake Systems Using Composite Friction Materials Containing Thermoplastic Elastomers (TPEs) by Mohsen Masoomi; Ali Asghar Katbab; Hossein Nazockdast (pp. 305-319).
Attempts have been made for the first time to prepare a friction material with the characteristic of thermal sensitive modulus, by the inclusion of thermoplastic elastomers (TPE) as viscoelastic polymeric materials into the formulation in order to the increase the damping behavior of the cured friction material. Styrene–butadiene–styrene (SBS), styrene–ethylene–butylene–styrene (SEBS) and nitrile rubber/polyvinyl chloride (NBR/PVC) blend system were used as TPE materials. In order to evaluate the viscoelastic parameters such as loss factor (tan δ) and storage modulus (E′) for the friction material, dynamic mechanical analyzer (DMA) were used. Natural frequencies and mode shapes of friction material and brake disc were determined by modal analysis. However, NBR/PVC and SEBS were found to be much more effective in damping behavior. The results from this comparative study suggest that the damping characteristics of commercial friction materials can be strongly affected by the TPE ingredients. This investigation also confirmed that the specimens with high TPE content had low noise propensity.
Keywords: thermoplastic elastomer (TPE); friction material; noise; SBS; NBR/PVC; SEBS
Development and Assessment of a New CFRP Rod–Anchor System for Prestressed Concrete by A. Al-Mayah; K. Soudki; A. Plumtree (pp. 321-334).
Design concepts and experimental assessment of a new wedge anchor system for prestressing CFRP rods are presented. This compact and reusable anchor consists of an outer cylinder (barrel), a number of wedges, and a soft metal sleeve. The contacting surfaces of the wedges and barrel have a circular profile along the length of the anchor. Tensile testing using different presetting loads, geometric configurations, and rod sizes was carried out. The relationship of the tensile load and displacement of the rod was established. Presetting was found unnecessary since the anchor system was found to be capable of carrying the full design strength of the rods.
Keywords: anchor; CFRP; contact pressure; copper; hardness; interfacial stress; presetting
Mathematical Analysis of Resin Flow through Fibrous Porous Media by Young Seok Song (pp. 335-343).
Resin flow through fiber preforms was analyzed mathematically. Closed form solutions for fiber volume fraction distribution and pressure field during resin infusion into fiber preforms were suggested, and a new effective permeability was defined. The effect of preform compressibility on the fiber volume fraction and pressure distributions in resin-saturated region was investigated analytically. The findings show that the compaction behavior of preforms has significant impact on the resin infusion process. The solutions derived analytically in this study can provide insight into a liquid composites molding (LCM) process.
Keywords: permeability; resin infusion