Water passes through a geotextile at the required rate but soil is found in the drainage core. Which filter function needs attention?
A Soil retention
B Surface decoration
C Thermal insulation
D Ultraviolet protection
Answer: A. Soil retention. Adequate water flow does not show whether the filter is retaining the required soil particles.
In fibrous filtration, why can the most penetrating particle size lie between very small and very large sizes?
A Different capture mechanisms dominate
B All sizes penetrate equally
C Only size exclusion occurs
D Fibres lose all charge
Answer: A. Different capture mechanisms dominate. Diffusion can help collect very small particles while interception and impaction tend to favour larger particles. Capture may be weaker between those regimes.
In a 30 cm³ laminate, fibre volume is 15 cm³ and matrix volume is 12 cm³. What is the void fraction?
A 40%
B 10%
C 90%
D 3%
Answer: B. 10%. Remaining volume is 3 cm³. Divide it by 30 cm³.
Along a two-metre uniform conductive textile track, resistance is 5 Ω per metre. Find total resistance.
A 5 Ω
B 2.5 Ω
C 10 Ω
D 20 Ω
Answer: C. 10 Ω. For a uniform track, resistance equals resistance per length multiplied by the length.
Why is a geotextile’s apparent opening size considered with soil gradation?
A To grade garment style
B To calculate yarn twist
C To assess retention compatibility
D To set dye bath speed
Answer: C. To assess retention compatibility. The suitability of an opening size depends on the particle sizes it must retain and the application conditions.
After resin cures around a flexible dry tow, the panel becomes much stiffer. What structural function does the matrix provide?
A Removes every reinforcing fibre
B Increases yarn count variation
C Reduces fibre fineness mechanically
D Maintains fibre arrangement
Answer: D. Maintains fibre arrangement. The cured matrix holds reinforcement in place and transfers load between fibres, allowing them to work together in the panel.
Stretching an open knit enlarges its gaps. How might UV transmission change?
A It always halves
B It always becomes zero
C It becomes independent of stretch
D It can increase
Answer: D. It can increase. Larger openings can allow additional radiation through the fabric.
Across a uniform 2 m strip, geotextile resistance is 18 kN per metre of width. Using uniform loading, what total tensile force corresponds to that rating?
A 36 kN
B 18 kN
C 20 kN
D 9 kN
Answer: A. 36 kN. The force-per-width value multiplied by the width gives the corresponding total force.
Why should a retroreflective tape test report illumination and observation angles?
A The fibre dimensions always change
B Return intensity depends on geometry
C Textile absorbs all visible light
D The tape changes chemical formula
Answer: B. Return intensity depends on geometry. Retroreflective performance depends on the positions of the light source and detector relative to the surface.
Which direction of water movement is evaluated in a normal-to-plane permeability test on a geotextile?
A Across its thickness
B Across its width only
C Along its length only
D Around its edge only
Answer: A. Across its thickness. Normal-to-plane flow passes perpendicular to the sheet face.
Volumetric air flow through a 0.30 m² filter face is 0.60 m³/s. What is face velocity?
A 2.0 m/s
B 0.5 m/s
C 0.18 m/s
D 6.0 m/s
Answer: A. 2.0 m/s. Face velocity is volumetric flow divided by exposed area.
Why might a conductive textile with an intact outer fabric stop transmitting signals after repeated folds?
A Fibre shade is more uniform
B All stitches become thermal insulation
C Conductive path develops cracks
D Fabric pilling always improves
Answer: C. Conductive path develops cracks. A conductive yarn or coating can suffer discontinuities even when the structural textile remains visually intact.
What does it demonstrate when an aligned composite is much stiffer along its fibres than across them?
A Unchanged capillary uptake
B Anisotropy
C Perfect isotropy
D Uniform UV absorption
Answer: B. Anisotropy. The properties depend on the measurement direction because reinforcement orientation is directional.
If measured UPF is 25, about what effective fraction of incident UV is transmitted under the test weighting?
A 25%
B 4%
C 96%
D 75%
Answer: B. 4%. UPF 25 is associated with a weighted transmitted fraction of approximately 1/25.
During placement, a geotextile tears around sharp particles even though its normal-flow test had passed. Which separate performance property was inadequate?
A Moisture wicking along fabric
B Permeability under stationary flow
C Colour retention after washing
D Installation damage resistance
Answer: D. Installation damage resistance. A textile must withstand handling and installation loads before it can perform its intended long-term function.
Two sports fabrics wick water equally fast, but one remains wet longer. What should be measured to explain the difference?
A Drying rate
B Filter dust load
C Yarn twist direction only
D Fabric print repeat
Answer: A. Drying rate. Wicking and drying are separate. One moves liquid while the other describes the rate it leaves the material.
Reinforcing fibres occupy 120 cm³ in a 200 cm³ composite specimen. Find the fibre volume fraction.
A 12%
B 120%
C 60%
D 40%
Answer: C. 60%. Divide the fibre volume by the total composite volume.
For a laboratory filter test, particle count is 2,000 upstream and 100 downstream in equal sampled air volumes. Find collection efficiency.
A 90%
B 95%
C 5%
D 80%
Answer: B. 95%. One hundred out of 2,000 particles pass through. The captured fraction is 1 − 0.05 = 0.95.
For an automotive webbing trial, purpose is to compare resistance to repeated bending. Which test programme fits?
A Static dye bath immersion
B One microscopic fibre identification
C Cyclic flex testing
D Single shade comparison
Answer: C. Cyclic flex testing. Repeated bending simulates flex cycles and can reveal damage that a single load or colour check would not.
Soil presses against a drainage geocomposite over time. What can restrict in-plane flow?
A Better fibre–matrix adhesion
B Visible weave colour change
C Greater wet yarn twist
D Compression of drainage channels
Answer: D. Compression of drainage channels. Compression can reduce the size or continuity of the pathways in the drainage core.
During repeated saline absorption, a hygiene core wets more slowly at the second dose. Which nonwoven function near the top is useful to examine?
A Outdoor UV protection
B Pressure drop for dry air
C Liquid acquisition and distribution
D Structural tensile reinforcement
Answer: C. Liquid acquisition and distribution. The acquisition layer transfers fresh liquid into the core. It can determine how quickly another dose is accepted.
When dry spots remain after resin infusion, which production requirement has not fully been met?
A Fabric heat setting only
B Permanent textile wicking
C Complete resin impregnation
D Colour registration of screens
Answer: C. Complete resin impregnation. The regions with dry fibres show that resin did not reach or wet all of the reinforcement.
What mechanism captures particles that follow streamlines but pass close enough to touch a fibre?
A Inertial impaction only
B Interception
C Electrodeposition only
D Brownian diffusion only
Answer: B. Interception. Interception occurs when a particle’s finite size brings it into contact with a fibre near its streamline.
At the same airflow, a loaded fabric filter gives a larger pressure drop than a clean one. Which cause is consistent with this observation?
A Fabric became fully permeable
B Particles gained no mass
C The ventilation pressure disappeared
D Flow paths have narrowed
Answer: D. Flow paths have narrowed. Deposits can increase resistance by blocking portions of the available pore network.
In a protective layered garment, what should be measured to compare the heat-flow resistance of two complete assemblies?
A Warp beam height
B Fabric print viscosity
C Single yarn colour
D Thermal resistance
Answer: D. Thermal resistance. The overall thermal resistance accounts for how layers and air spaces impede heat flow under the stated test.