Polymers and Composite Materials Flashcards

Degree of polymerization (DP) is defined as:

Answer: The number of repeat units in a polymer chain

The degree of polymerization is the number of monomer repeat units in a single polymer chain, related to molecular weight by DP = M_n / m (repeat unit mass).

Which of the following is a thermoplastic polymer commonly used in engineering applications for its high impact strength and transparency?

Answer: Polycarbonate (PC)

Polycarbonate is a thermoplastic known for high impact resistance, optical clarity, and good thermal stability, widely used in safety glazing and electronic housings.

In polymer science, creep refers to:

Answer: Time-dependent deformation under sustained stress below the yield point

Creep in polymers is the slow, time-dependent increase in strain under a constant applied stress, driven by viscoelastic flow of polymer chains.

The critical fiber length in a fiber composite is the minimum fiber length required to:

Answer: Allow full load transfer from matrix to fiber so the fiber can reach its tensile strength

The critical fiber length is the minimum length needed for the shear stress at the fiber-matrix interface to transfer enough load to bring the fiber to its failure stress.

Delamination in laminated composite structures most commonly initiates at:

Answer: Free edges and ply drop-offs due to interlaminar stresses

Delamination preferentially initiates at free edges, ply terminations, and ply drop-offs where interlaminar normal and shear stresses are highest.

Which composite manufacturing process uses vacuum pressure to infuse resin into a dry fiber preform?

Answer: Vacuum-assisted resin transfer molding (VARTM)

VARTM (Vacuum-Assisted Resin Transfer Molding) uses vacuum pressure to draw liquid resin through a dry fiber preform placed in a one-sided mold under a vacuum bag.