This set of Composite Materials Multiple Choice Questions & Answers (MCQs) focuses on “Fiber Content, Density and Void Content”.
1. The fiber weight fraction can be experimentally determined by ____________
a) ASTM D3171
b) ASTM D3172
c) ASTM D3039
d) ASTM D3951
View Answer
Explanation: The test is typically intended for two-component materials. The test method ASTM D3171, which is the matrix digestion method, provides two ways for determining the constituent content of composite materials. Method I removes the matrix by ignition or digestion. Method II is only for laminates and calculations are based on thickness.
2. What does ASTM stand for?
a) American Society for Testing and Materials
b) American Standard for Testing and Materials
c) American System for Testing and Materials
d) American Standard for Testing and Making
View Answer
Explanation: American Society for Testing and Materials is an international standards organization that develops and publishes technical standards for a broad range of products, materials, services and systems. It was founded in 1898 and its headquarters located in Pennsylvania, United States.
3. The ____________ is used for PMC-containing fibers that do not lose weight at high temperatures, such as glass fibers.
a) matrix digestion method
b) ignition loss method
c) flexure method
d) void content test
View Answer
Explanation: The ignition loss method consists of strongly igniting a material at a specific temperature, permitting the volatile substances to burn away, until its mass stops to change. This process may be done in the air or inert atmosphere or in some other reactive atmosphere.
4. What is ASTM D2584?
a) Test Method for Ignition Loss of Cured Reinforced Resins
b) Test Methods for Constituent Content of Composite Materials
c) Test Methods for Constituent Content of Composite Prepreg
d) Test Method for Tensile Properties of Polymer Matrix Composite Materials
View Answer
Explanation: The fiber weight fraction can be determined by the ignition loss test method. The matrix digestion method (ASTM D3171) method can be also employed for the determination of weight fraction.
5. Which liquid medium is used for dissolving matrix in matrix digestion method?
a) Sulfuric acid
b) Conc. Nitric acid
c) Hydrochloric acid
d) Perchloric acid
View Answer
Explanation: By the addition of nitric acid into the sample material, it get dissolved until the total decomposition of the matrix phase. Adding nitric acid converts the metal ions into their nitrate salts, which are highly soluble.
6. Which standard can be used for determining the fiber volume fraction by comparing the electrical resistivity of the composite with the fibers?
a) ASTM D3039
b) ASTM D3359
c) ASTM D3355
d) ASTM D3350
View Answer
Explanation: ASTM D3355 is a method of test for fiber content of unidirectional fiber-resin composites by electrical resistivity. This method is employed for the unidirectional composites containing electrically conductive fibers in a non-conductive matrix.
7. A high void content usually leads to lower fatigue resistance.
a) True
b) False
View Answer
Explanation: A high void content not only lowers the fatigue resistance but also leads to greater susceptibility to water diffusion and increased variation in mechanical properties.
8. ____________is defined as the arrangement of fibers in a composite, which not only influences the properties of the composite but also it’s processing.
a) Fiber architecture
b) Fiber planning
c) Fiber alignment
d) Fiber engineering
View Answer
Explanation: The properties of the composite is greatly influenced by the fiber architecture. The mechanical properties are influenced by the characteristics like fiber continuity, fiber orientation, fiber crimping and fiber interlocking.
9. The pores that remain unfilled with fibers and polymer in a composite material is called voids.
a) False
b) True
View Answer
Explanation: Composite voids are formed as a result of the poor manufacturing of the material. Voids adversely affect the lifespan and mechanical properties of the composite.
10. Which of the method cannot be used to determine fiber volume fractions?
a) Matrix digestion
b) Ignition loss method
c) Optical microscopy-based techniques
d) Pultrusion
View Answer
Explanation: Pultrusion is a composite manufacturing technique while all others are the methods used for the determination of fiber volume fractions. Matrix digestion involves polymer matrix digestion using a strong acid specifically nitric acid. Ignition loss method involves igniting the matrix phase completely by keeping the fiber phase remaining. Polarized light is an important optical microscopy-based technique used for fiber volume fraction determination.
Sanfoundry Global Education & Learning Series – Composite Materials.
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