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Reinforcing Fibers (reinforcing + fiber)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Increased Interface Strength in Carbon Fiber Composites through a ZnO Nanowire Interphase

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2009
Yirong Lin
Abstract One of the most important factors in the design of a fiber reinforced composite is the quality of the fiber/matrix interface. Recently carbon nanotubes and silicon carbide whiskers have been used to enhance the interfacial properties of composites; however, the high growth temperature degrade the fiber strength and significantly reduce the composite's in-plane properties. Here, a novel method for enhancing the fiber/matrix interfacial strength that does not degrade the mechanical properties of the fiber is demonstrated. The composite is fabricated using low-temperature solution-based growth of ZnO nanowires on the surface of the reinforcing fiber. Experimental testing shows the growth does not adversely affect fiber strength, interfacial shear strength can be significantly increased by 113%, and the lamina shear strength and modulus can be increased by 37.8% and 38.8%, respectively. This novel interface could also provide embedded functionality through the piezoelectric and semiconductive properties of ZnO. [source]

Characterization and design of interphases in glass fiber reinforced polyproplyene

POLYMER COMPOSITES, Issue 3 2000
E. Mäder
Bond strength between reinforcing fibers and polymer matrices can be controlled in two ways: 1) by intensification of molecular interaction at the interface and 2) by creation of a strong transition layer (interphase) between the components. In this paper, we consider the possibilities of controlling interfacial strength by means of target-oriented variation of structure, thickness and strength of the interphase artificially created between the glass fiber and the polypropylene matrix. The bond strength was measured using a continuously monitored microbond test, including recording the crack length as a function of the load applied. The measured interfacial strengths correlated to the macromechanical properties of glass fiber reinforced polypropylene. The interphase design provided simultaneous increase in the tensile strength and the impact toughness of the composites. [source]

Time-cure-temperature superposition for the prediction of instantaneous viscoelastic properties during cure

POLYMER ENGINEERING & SCIENCE, Issue 6 2000
Yongsung Eom
The relative sequence of shrinkage and evolution of modulus of a thermoset resin during cure leads to the build-up of internal stresses, especially if the resin is constrained by the presence of other materials in the form of a substrate or reinforcing fibers. To enable prediction of the levels of internal stress generated during processing and to determine appropriate processing windows, the evolution of the modulus of an epoxy-amine system during cure has been characterized and described with a phenomenological model. A combined reaction kinetics model is used to determine the degree of conversion of the epoxy over any complete range of cure. The chemorheological properties of the resin are measured as a function of curing temperature with a torsional parallel plate rheometer. A new phenomenological approach for time-cure-temperature superposition is proposed for predicting the relaxation modulus at any moment during cure and at any cure temperature. The combination of these two models provides a full description of the instantaneous viscoelastic properties during cure. This approach, which can be adapted to any curing resin, provides suitable tools for the analysis of viscoelastic stress build-up following any industrially relevant cure cycle. [source]

Controlling the properties of single-polymer composites by surface melting of the reinforcing fibers,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10-12 2002
D. M. Rein
Abstract All-thermoplastic single-polymer composites are materials in which both the reinforcing fibrous phase and the matrix between them are made of the same thermoplastic polymer. Excellent bonding is achieved by mutual entanglement macromolecules due to controlled surface melting of the fibers. This results in a uniform structure of a single chemical entity. The physical properties of the consolidated material, such as modulus and coefficient of thermal expansion (CTE), can be controlled by the extent of melting effected in the process, which determines the fiber/matrix ratio. The fabrication technology utilizes oriented polymer fibers in various forms: unidirectional lay-up, woven fabric or chopped fibers/non-woven felt. The key element in the processing scheme is the control of the fibers' melting temperature by hydrostatic pressure. The fibers are heated under high pressure to a temperature that is below their melting point at the high pressure but above the melting temperature at some lower pressure. Reduction of pressure for controlled time results in melting of the fibers, which starts at the fiber surface. This surface melting under controlled pressure followed by crystallization produces the consolidated structure. We illustrate and describe this process using fibers of ultra-high-molecular-weight polyethylene (UHMWPE), showing the effect of the processing conditions on the flexural modulus, fiber/matrix ratio, and CTE in plane and in the thickness direction. These properties are relevant to the use of such composites as substrates for microwave antennae. Copyright © 2003 John Wiley & Sons, Ltd. [source]