Chapter 3 Fibers_MSE 404

What are aramid fibers and give examples?

Aramid fibers are aromatic polyamide fibers such as Kevlar® by Du Pont Co. and Twaron® by AKZO Co.

List two advantages of aramid fibers.

Light weight (1.44 g/cm3) and high toughness.

What are two disadvantages of aramid fibers?

Low compressive strengths and poor adhesion to matrix.

How are aramid fibers manufactured?

Through solution polycondensation of p-phenylene diamine and terephthaloyl chloride, followed by spun extrusion and stretching.

Describe the structure of aramid fibers.

They have skin-core structures with highly oriented rigid linear molecular chains, providing high longitudinal strength and low transverse strength.

What is the modulus of aramid fibers compared to conventional nylon fibers?

Over 20 times greater than conventional nylon fibers.

What applications are suitable for aramid fibers?

Ballistic protection (e.g., bullet-proof vests), composites armor for ships, combat vehicles, and helicopters.

What does UHMWPE stand for and provide examples?

Ultrahigh Molecular Weight Polyethylene; examples include Spectra® fibers by Honeywell Co. and Dyneema® fibers by DSM Co.

What are the advantages of UHMWPE fibers?

Lowest weight (0.97 g/cm3), highest specific strength and modulus, outstanding toughness, and good solvent resistance.

List two disadvantages of UHMWPE fibers.

Low compressive strengths and poor adhesion to matrix.

What is the manufacturing process of UHMWPE fibers?

It involves using high density polyethylene with a high degree of drawing.

What applications are suitable for UHMWPE fibers?

Marine tow ropes, mooring cables, fishing nets, medical devices, and soft and rigid composite armors.

What are some features of UHMWPE fibers in space applications?

They have high shielding effectiveness to space radiation.

What are the definitions of fibers, filaments, and strands in the context of reinforcement forms?

Fibers are general long-axis materials; filaments are single fibers; strands are imprecise bundles of untwisted filaments.

What is meant by woven fabric?

A planar material made by interlacing yarns or tows in various specific patterns.

What are hybrid fabrics?

Fabrics that use more than one type of fiber providing better comprehensive performance.

Give an example of a hybrid fabric and its properties.

Carbon/Aramid: High compressive and tensile strength combined with high impact resistance.

What are fibers in the context of reinforcement forms?

Fibers are a general term for materials that have a long axis.

What is a filament?

A filament is a single fiber.

What is a strand?

A strand is an imprecise bundle or group of untwisted filaments.

What is a tow?

A tow is an untwisted bundle with a specific count (such as 12K).

What is roving?

Roving is a number of yarns or tows collected into a parallel bundle without twisting.

What is tape in the context of reinforcement materials?

Tape is a collection of parallel filaments held together by a binder (matrix of the composite).

What is a yarn?

A yarn is a twisted tow, often used for weaving.

What is a woven fabric?

A woven fabric is a planar material made by interlacing yarns or tows in various specific patterns.

What is braiding?

Braiding is the interlacing of yarns or tows into a tubular shape instead of a flat fabric.

What is a mat?

A mat is a sheet-like material consisting of randomly oriented chopped fibers or swirled continuous fibers held together loosely by a binder.

What are hybrid fabrics?

Fabrics that use more than one type of fiber providing better comprehensive performance.

Describe the properties of Carbon/Aramid hybrid fabrics.

They offer high compressive and tensile strength, high impact resistance, and are known for their high cost.

What is a key feature of Aramid/Glass hybrid fabrics?

They have low density, high impact resistance, tensile strength, and provide good compressive and tensile strength at a low cost.

What are the properties of Carbon/Glass hybrid fabrics?

They feature high tensile and compressive strength, stiffness, low density, and are available at a low cost.