CHAPTER 6- FIBERS
Fibers
1. ________________________________________________________
2. ________________________________________________________
3. ________________________________________________________
4. Can be characterized based on comparison of both physical and
chemical properties
Fabric
1. ________________________________________________________
2. ________________________________________________________
3. Types of fibers and fabric:
- Natural—____________________________________________
- Artificial—____________________________________________
Types of Fibers
Synthetic
__________________
__________________
__________________
__________________
__________________
__________________
Natural
_____________________
_____________________
_____________________
_____________________
_____________________
Classification
Natural fibers are classified according to their origin:
1. ________________________________________________________
2. ________________________________________________________
3. ________________________________________________________
Cellulose Fibers
1. Cotton—_________________________________________________
________________________________________________________
2. Rayon—_________________________________________________
________________________________________________________
3. Cellulose acetate—________________________________________
________________________________________________________
Fiber Comparison
Describe the difference(s) between the cotton on the left and the rayon on
the right.
____________________________________________________________
____________________________________________________________
____________________________________________________________
Protein Fibers
1. Wool—__________________________________________________
________________________________________________________
________________________________________________________
2. Silk—___________________________________________________
________________________________________________________
Mineral Fibers
1. Asbestos—______________________________________________
________________________________________________________
2. Rock wool—_____________________________________________
3. Fiberglass—_____________________________________________
Synthetic Fibers
Made from derivatives of ________________________________________
1. Nylon—_________________________________________________
2. Polyester—______________________________________________
3. Acrylic—________________________________________________
4. Spandex—_______________________________________________
Man-made Fibers
Fibers derived from ____________________________________________
–
–
SUMMARY QUESTIONS:
Read p. 128-135 in the textbook
1) Why are fibers valuable at a crime scene?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
2) How do fibers have probative value?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
3) How are fabrics made?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
4) What are the different characteristics of a fiber, a filament & a fabric?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
5) Are inorganic fibers natural or synthetic? Name two.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Fabric Production
1. ________________________________________________________
________________________________________________________
________________________________________________________
2. Most are either ______________ or ________________
3. ________________________________________________________
________________________________________________________
________________________________________________________
Weave Terminology
1. Yarn—__________________________________________________
________________________________________________________
2. Warp—__________________________________________________
3. Weft—__________________________________________________
4. Blend—_________________________________________________
________________________________________________________
Weave Patterns
Plain Weave
1. ________________________________________________________
2. ________________________________________________________
3. Design resembles a _____________________
Twill Weave
1. ________________________________________________________
________________________________________________________
2. ________________________________________________________
3. Design resembles ____________________
4. _____________ is one of the most common examples.
Satin Weave
1. ________________________________________________________
2. ________________________________________________________
3. ________________________________________________________
4. ___________ is the most obvious example
Knitted Fabric
1. ________________________________________________________
________________________________________________________
2. It may be one continuous thread or a combination.
3. ________________________________________________________
________________________________________________________
________________________________________________________
Polymers
1. Synthetic fibers are made of _________________________________
________________________________________________________
2. The word polymer means many (poly) units (mer).
3. ________________________________________________________
4. By varying the ________________________________________ or by
_____________________________________, polymers are created
that have different properties.
5. As a result of these differences, they can be distinguished from one
another forensically.
Filament Cross Sections
1. ________________________________________________________
________________________________________________________
2. The holes of the nozzle are not necessarily round; therefore, the fiber
filament may have a unique shape in cross section.
Round
4-lobed
Octalobal
Trilobal
Irregular
Dogbone or
Dumbbell
Multi-lobed
or Serrate
Summary Questions:
Read p. 136-143 in the textbook
1. What is the monomer of a polymer?
___________________________________________________________________
___________________________________________________________________
2. What is the monomer of wool? In silk? In cotton?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
3. List four synthetic fibers.
___________________________________________________________________
4. What is the most common natural fiber used in textiles? The most common
synthetic fiber?
___________________________________________________________________
___________________________________________________________________
5. Why does wool have a distinctive smell when it is burned?
___________________________________________________________________
___________________________________________________________________
6. How is silk produced?
___________________________________________________________________
___________________________________________________________________
7. Why is silk a simpler structure than wool?
___________________________________________________________________
___________________________________________________________________
8. What is rayon?
___________________________________________________________________
___________________________________________________________________
9. How are acetate fibers made? What products are formed from acetate fibers?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
10. Why was the discovery of Nylon 66 important?
___________________________________________________________________
___________________________________________________________________
11. Which of the fabrics found in Activity 6.3 would have the most probative value in
an investigation? Which would have the least? Explain.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
12. How are the properties of a linear polymer different from a cross-linked polymer?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
13. Identify the two types of acrylic fibers and their uses.
___________________________________________________________________
___________________________________________________________________
14. What is the structure of spandex (Lycra)
What is the significance of fiber evidence?
1. Can prove _______________________________________________
2. Can prove _______________________________________________
3. Value is dependent on:
• ________________________________________________
• ________________________________________________
• ________________________________________________
• ________________________________________________
Fiber as trace evidence
Primary Transfer
____________________________
____________________________
____________________________
Secondary Transfer
____________________________
____________________________
____________________________
Using fibers to reconstruct crime scenes
1. ________________________________________________________
2. The _________ & ___________________ of the fabric.
3. Mobility of victim
____________________________________________________
4. The length of time between actual physical contact.
__________________________________________________________
______________________________________________
Testing for Identification
1. Microscopic observation
2. Burning — ______________________________________________
________________________________________________________
3. Thermal decomposition — _________________________________
________________________________________________________
4. Chemical tests — _________________________________________
5. Density — the _____ of an object divided by the ______ of the object
6. Refractive index — _______________________________________
________________________________________________________
7. Fluorescence — __________________________________________
________________________________________________________
Dyes
1. Components that make up dyes can be separated and matched to an
unknown.
2. There are more than ______________________________________
3. ________________________________________________________
4. ________________________________________________________
________________________________________________________
Collection of Fiber Evidence
1. ________________________________________________________
________________________________________________________
________________________________________________________
2. ________________________________________________________
________________________________________________________
3. ________________________________________________________
________________________________________________________
Fiber Evidence
1. ________________________________________________________
________________________________________________________
2. In the case of Wayne Williams, fibers weighed heavily on the outcome
of the case. Williams was convicted in 1982 based on carpet fibers that
were found in his home, in his car, and on several murder victims.
Problems with Fiber Evidence
1. Class Characteristic
____________________________________________________
2. The less common the fiber the more useful it is to identify a suspect.
__________________________________________________________
______________________________________________
Basic Comparison of Fiber Samples
1. ________________________________________________________
2. ________________________________________________________
3. ________________________________________________________
4. ________________________________________________________
5. ________________________________________________________
Summary Questions:
Read p. 144-161 in the textbook
1) Can a fiber be individualized to a particular textile fabric? Why of how?
___________________________________________________________________
___________________________________________________________________
2) Can a piece of fabric be individualized to a particular garment? Why or how?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
3) If an unknown fiber is suspended in a solution with a density of 1.30, what might the
fiber be?
___________________________________________________________________
4) If the same fiber in question 3 is found to have a refractive index of 1.53, what might
it be?
___________________________________________________________________
5) How is the Becke line used to determine Refractive Index?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
6) Explain how an optical brightener may change how light reacts with fibers.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
7) If a fiber disappears in castor oil, what might it be?
___________________________________________________________________
8) How is chromatography used in identifying the make up of dyes?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
9) What is trace evidence? What is the common basis for analyzing trace evidence,
that is, what are the goals?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
10) During a trial, what are the primary concerns in analyzing and using extremely
small bits of trace evidence?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
11) How do forensic scientists use FTIR to analyze fibers?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
12) How does the FBI use a crook’s jeans to catch them?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
13) How did Fibers & their analysis play a major role in the Amanda Davis case?
___________________________________________________________________
___________________________________________________________________
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