Composite Materials Questions and Answers – Fiber Surface Treatment

This set of Composite Materials Multiple Choice Questions & Answers (MCQs) focuses on “Fiber Surface Treatment”.

1. Common coupling agents used with glass fibers are organofunctional silicon compounds, known as _______
a) silicates
b) silicones
c) silanes
d) silanol
View Answer

Answer: c
Explanation: Chemical coupling agents are used with glass fibers to improve the fiber-matrix interfacial strength through physical and chemical bonds and protect the fiber surface from moisture and reactive fluids. Silanes are used in composites to improve electrical properties and mechanical strength. Silanes care used to increase resistance to abrasions, increase thermal stability, increased adhesion resistance and crosslinking in paints, inks etc.

2. The chemical formula of silanes is __________
a) SiO44-
b) SiH4
c) SiH4O
d) SiH2
View Answer

Answer: b
Explanation: Silane is a colorless inorganic compound with a repulsive smell similar to acetic acid. The other compounds of silicon are: SiO44- is a silicate, SiH4O is silanol and SiH2 is silylenes.

3. Which of the following is a silane coupling agent for glass fiber-reinforced epoxy polymer?
a) Vinyl triethoxysilane
b) Vinyl tris(β-methoxyethoxy)silane
c) Γ-Glycidyloxypropyltrimethoxysilane
d) Γ-Methacryloxypropyltrimethoxysilane
View Answer

Answer: c
Explanation: Silanes, the organofunctional silicon compounds are the common coupling agents used with glass fibers. Their chemical structure is represented by R’ – Si(OR)3, in which the functional group R’ must be compatible with the matrix resin in order for it to be an effective coupling agent. The reinforcement properties are directly affected by the compatibility between coupling agent and matrix.

4. The matrix shrinks considerably more than the fibers as both cool down from the high processing temperature.
a) True
b) False
View Answer

Answer: a
Explanation: The thermal expansion coefficient of the polymer matrix is nearly 10 times greater than that of the reinforcement fibers. As a result, the matrix shrinks considerably more than the fibers when they are cooled down from a higher temperature.

5. Which of the following is not true about the surface treatment?
a) Promote good chemical bonding of fibers with the polymer matrix
b) Increase the surface area by creating micropores or surface pits
c) Provides a larger number of contact points for fiber–matrix bonding
d) Decrease strength of the composite
View Answer

Answer: b
Explanation: Fiber surface treatment’s primary function is to improve the fiber surface wettability and to create a strong bond at the fiber surface interface. This is essential for the effective stress transfer between the matrix and fiber reinforcement. Fiber surface treatment also increases the surface area by creating micropores or surface pits on carbon fiber surface which helps in providing a larger number of contact points for fiber-matrix bonding.

6. Which of the following functional group does the oxidative surface treatment doesn’t produce?
a) Carboxylic
b) Phenolic
c) Sulfhydryl
d) Hydroxylic
View Answer

Answer: c
Explanation: The acidic functional groups, such as carboxylic, phenolic, and hydroxylic are produced by oxidative surface treatment on the carbon fiber surface. They may be carried out either in an oxygen-containing gas or in a liquid such as nitric acid, sodium hypochloride. Since sulfhydryl is a basic functional group it can’t be produced by the oxidative surface treatments.

7. Which of the following is a silane coupling agent for glass fiber-reinforced polyester polymer?
a) Γ-Aminopropyltriethoxysilane
b) Γ-Glycidyloxypropyltrimethoxysilane
c) N-β-Aminoethyl-Γ-aminopropyltrimethoxysilane
d Vinyl triethoxysilane
View Answer

Answer: d
Explanation: Cloudburst is the process where hybrid cloud expand itself to the public cloud when more computing resources are required.

8. The extent of strength improvement of a composite material depends on the compatibility of the __________with the matrix resin.
a) reinforcement
b) coupling agent
c) filler
d) binders
View Answer

Answer: c
Explanation: The function of a coupling agent is to create a chemical bond between dissimilar materials. It acts as an intermediate phase between materials, specifically organic and inorganic materials. The selection of the coupling agent is based upon its compatibility with the matrix phase. Greater the compatibility between matrix and coupling agent, greater the strength improvement of the composite.

9. Why the surface treatment of carbon fibre is said to be necessary?
a) It has less strength
b) It has less toughness
c) Its surface is chemically inactive
d) Low thermal expansion coefficient
View Answer

Answer: c
Explanation: Carbon fibers have an inert surface which acts as a hindrance in the bonding with the matrix phase. Fibre surface treatment can be adopted as a measure for activating the carbon fibre surface by forming surface functional groups.

10. Which of the following is not a characteristic of silane?
a) Colorless
b) Repulsive odour
c) Flammable
d) Non-toxic
View Answer

Answer: d
Explanation: Silane is a poisonous gas. It is a strong irritant to skin, mucous membrane and eyes. It is very toxic for inhalation and causes serious health issues even death. The processing of composites with silane, therefore, requires deep care and safety measures.

Sanfoundry Global Education & Learning Series – Composite Materials.

To practice all areas of Composite Materials, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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