COC Materials Science & Technology 2 — Questions and Answers
Question 1: The Shore A hardness scale is used to measure the hardness of which category of materials relevant to O&P?
- Soft elastomers and gel liners (Correct answer)
- Hard carbon fiber composites
- Aluminum alloys
- Rigid thermoplastics
Correct answer: Soft elastomers and gel liners
Shore A measures the hardness of soft rubbers, silicones, and gel materials, making it the standard for evaluating prosthetic liners and cushioning pads.
Question 2: Lamination resin systems in O&P typically consist of which two components mixed before application?
- Base resin and catalyst (hardener) (Correct answer)
- Monomer and solvent
- Pigment and filler
- Foam and adhesive
Correct answer: Base resin and catalyst (hardener)
Lamination resins are two-part systems where the base resin crosslinks when mixed with a catalyst or hardener to form a rigid composite structure.
Question 3: Silicone liner suspension for transtibial prostheses primarily functions through which mechanism?
- Locking pin or shuttle lock engaging a distal receptacle (Correct answer)
- Suction from a valve only
- Friction between liner and socket wall only
- Elevated vacuum from an external pump
Correct answer: Locking pin or shuttle lock engaging a distal receptacle
The most common silicone liner suspension uses a distal locking pin that clicks into a receiver in the socket, providing secure suspension.
Question 4: Which fiber orientation in a carbon fiber layup provides the greatest resistance to bending in a single direction?
- Unidirectional (0°) fibers aligned with the bending axis (Correct answer)
- Woven ±45° fibers
- Random chopped fiber mat
- Cross-ply (0°/90°) symmetric layup
Correct answer: Unidirectional (0°) fibers aligned with the bending axis
Unidirectional fibers aligned with the primary load axis provide maximum stiffness and strength in that direction by fully utilizing fiber tensile modulus.
Question 5: Creep in thermoplastic orthotic materials refers to:
- Slow permanent deformation under sustained load over time (Correct answer)
- Rapid elastic rebound after load removal
- Sudden fracture at yield stress
- Increased stiffness with repeated loading cycles
Correct answer: Slow permanent deformation under sustained load over time
Creep is the time-dependent, progressive deformation of a material under constant stress, which can cause orthotics to lose their molded shape over months of use.
Question 6: What is the primary purpose of a check socket in prosthetic fitting?
- To evaluate fit, alignment, and function before fabricating the definitive socket (Correct answer)
- To provide a temporary prosthesis during healing
- To protect the residual limb during wound care
- To measure volume changes during therapy
Correct answer: To evaluate fit, alignment, and function before fabricating the definitive socket
A check socket (diagnostic socket) made of clear thermoplastic allows visual inspection of pressure points and confirms fit before the definitive socket is fabricated.
COC Materials Science & Technology 2
The Shore A hardness scale is used to measure the hardness of which category of materials relevant to O&P?