Molding of Oriented Short-Fiber Composites. II. Flow Through Convergent Channels

Molding of Oriented Short-Fiber Composites. II. Flow Through Convergent Channels
Author: Lloyd A. Goettler
Publisher:
Total Pages: 53
Release: 1974
Genre:
ISBN:

Superior mechanical properties can be attained in a short fiber composite by utilizing the flow in transfer or injection molding to align the fibers into the direction of highest stress. This is best accomplished in an elongational flow field, such as occurs in a converging channel. A MODEL IS DERIVED TO DESCRIBE THE CHANGES IN ORIENTATION DISTRIBUTION RESULTING FROM THIS FLOW. We investigated the effects of the geometric, material, and processing variables on the orientation parameters of this model, the resulting orientation level and the tensile modulus of molded rods. (Author-PL).

Molding of Oriented Short Fiber Composites. III. Rate Effects on Fiber Alignment in Convergent Channels

Molding of Oriented Short Fiber Composites. III. Rate Effects on Fiber Alignment in Convergent Channels
Author: L. A. Goettler
Publisher:
Total Pages: 68
Release: 1974
Genre:
ISBN:

In an extension of the experiments performed on the compacted flow of a glass fiber- filled epoxy resin through a conical converging channel under a high pressure, this study examines the orientability of the fibers as the suspension flows into an expty mold cavity. The tensile properties of molded rods of 1/46 to 1/26 diameter reflect the level of orientation produced. Both the fiber orientability and the resulting orien- tation distribution depend strongly on the rate of elongation. The molded-in orientation distribution is also determined by the extent of convergence. Convergence angle, viscosity, and fiber length are secondary variables. The results indicate that fibers can be oriented to within 20^ of the flow axis by this technique in order to maximize mechanical performance. The anomalous dependence on the rate of elongation is thought to result from the high voidate in the material during flow. (Author-PL).

Flow Orientation of Short Fibers in Rectangular Channels

Flow Orientation of Short Fibers in Rectangular Channels
Author: Masaharu Takano
Publisher:
Total Pages: 40
Release: 1974
Genre:
ISBN:

Fabrication of composites from discontinuous fibers are found to pose many rheological problems, especially when fibers are short and their orientation and distribution have to be controlled by a flow process. The effects of fiber concentration, die-geometry and flow rate on the translational and rotational motions of short fibers in concentrated suspensions are determined from cinematographic studies on model systems subjected to flow through uniform and convergent rectangular channels. Fiber concentration is varied from 60 vol.% to as low as 0.05 vol.%. The total convergence angle of the channels varies from 0 to 210 degrees; the channel thickness is comparable to or smaller than the fiber length. The viscosity of resin used is 55 p. When fiber concentration is higher than 5 vol%, a plug- type flow is observed in both uniform and convergent channels. However, the observed velocity of fibers is always smaller than the mean velocity of the flowing suspension. A stagnation region is observed in convergent channels when the convergence angle is larger than 120 degrees. The alignment of fibers in the flow direction exclusively occurs in convergent channels. Flow instabilities, migration of trapped air bubbles, generation of voids, deformation of fibers and flow properties are also observed. (Author-PL).

Molding of Oriented Short Fiber Composites. I. Ultimate Tensile Properties

Molding of Oriented Short Fiber Composites. I. Ultimate Tensile Properties
Author: Lloyd A. Goettler
Publisher:
Total Pages: 68
Release: 1972
Genre:
ISBN:

Several aspects of composite structure that affect the mechanical performance of polymers reinforced with short fibers are fiber length, fiber concentration, void content, dispersion of fibers, fiber orientation, and wetting. This report describes the dependence of these structural variables on the molding compound composition and on the processing conditions for flow (plunger) moldings of epoxy resin reinforced with short glass fibers. The methods used in this study for characterizing the composite structure are also presented. Since the primary structural variables mentioned above cannot in practice be changed independently, the measured tensile strengths and ultimate elongations of molded specimens are correlated directly with the preparation techniques and processing conditions used in their fabrication. It is found that voids, wetting, and dispersion are not critical when the fibers are properly aligned into the direction of highest stress. The fibers must be equal to or longer than one-eighth of an inch to sustain high loads in the epoxy system studied. (Author modified-PL).

Handbook of Composite Reinforcements

Handbook of Composite Reinforcements
Author: Stuart M. Lee
Publisher: John Wiley & Sons
Total Pages: 736
Release: 1996-12-17
Genre: Technology & Engineering
ISBN: 9780471188612

This comprehensive single volume handbook covers every aspect of reinforcement science, from hands-on subjects, such as manual 'lay-up' processing, to theoretical discussions concerning rheology and modeling. Taken from the recently published six volume International Encyclopedia of Composites, this reference volume offers scholarly and practical knowledge of distinguished industry-experts, academics, and government researchers in one accessible and informative handbook. Fibers, processes, and composite reinforcement types, as well as relevant miscellaneous subjects such as property relationships, manufacturing, hybrid reinforcements, and modeling are given detailed treatment. Engineers, materials scientists, and technologists will find the Composite Reinforcement Handbook an invaluable tool.

Mechanical Properties of Polymers and Composites, Second Edition

Mechanical Properties of Polymers and Composites, Second Edition
Author: Robert F. Landel
Publisher: CRC Press
Total Pages: 586
Release: 1993-12-14
Genre: Technology & Engineering
ISBN: 9780824789640

This text, now in its second edition, offers an up-to-date, expanded treatment of the behaviour of polymers with regard to material variables and test and use conditions. It highlights general principles, useful empirical rules and practical equations.;Detailing the specific behaviour of many common polymers, the text: places emphasis on time and frequency dependence over temperature dependence; uses contemporary molecular mechanisms to explain creep, stress relaxation, constant strain rate responses and crazing; provides explicit equations to predict responses; supplies a discussion of large deformation multiaxial responses; compares statistical and continuum theories on the same data set; and updates stress-strain behaviour and particulate filled systems.

Flow-Induced Alignment in Composite Materials

Flow-Induced Alignment in Composite Materials
Author: T.D. Papathanasiou
Publisher: Woodhead Publishing
Total Pages: 399
Release: 2021-10-19
Genre: Technology & Engineering
ISBN: 0128185759

The purpose of aligning short fibers in a fiber-reinforced material is to improve the mechanical properties of the resulting composite. Aligning the fibers, generally in a preferred direction, allows them to contribute as much as possible to reinforcing the material. The first edition of this book detailed, in a single volume, the science, processing, applications, characterization and properties of composite materials reinforced with short fibers that have been orientated in a preferred direction by flows arising during processing. The technology of fiber-reinforced composites is continually evolving and this new edition provides timely and much needed information about this important class of engineering materials. Each of the original chapters have been brought fully up-to-date and new developments such as: the advent of nano-composites and the issues relating to their alignment; the wider use of long-fiber composites and the appearance of models able to capture their orientation during flow; the wider use of flows in micro-channels in the context of composites fabrication; and the increase in computing power, which has made relevant simulations (especially coupling flow kinematics to fiber content and orientation) much easier to perform are all covered in detail. The book will be an essential up-to-date reference resource for materials scientists, students, and engineers who are working in the relevant areas of particulate composites, short fiber-reinforced composites or nanocomposites. - Presents recent progress on flow-induced alignment, modelling and design of fiber and particulate filled polymer composites - Discusses important advances such as alignment of CNTs in polymer nanocomposites and molecular alignment of polymers induced by the injection molding process in the presence of fillers such as short fibers - Presents fiber interaction/diffusion modelling and also the fiber flexure/breakage models