Composites

Question 1

Composite

Answer 1

two or more chemically distinct parts with interface b/w, discontinuous phase within continuous

Question 2

Discontinuous phase

Answer 2

harder, stronger, reinforcement material

Question 3

Continuous phase

Answer 3

matrix

Question 4

Desired mechanical properties

Answer 4

stiff, strong, tough, fatigue resistance

Question 5

Fibrous composite

Answer 5

better mechanical effectiveness than particulate in terms of strength, stiffness

Question 6

Particle reinforced composites

Answer 6

isotropic (same physical properties everywhere)

Question 7

Failure of composite

Answer 7

increase chance of exposing fibers/particles to surrounding biological environment, separation of interface to matrix, stress exceeding interface strength, fatigue

Question 8

Carbon fibers

Answer 8

lightweight, flexible, high strength, high elastic modules material, contain 93-95% carbon, graphite fiber = +99% carbon

Question 9

Main reinforcing materials

Answer 9

carbon fibers, polymer fibers, ceramics, glasses

Question 10

Carbon and graphite fibers

Answer 10

stiffer and stronger than steel
low density

poor shear strength

Question 11

Negative effects of medical devices using carbon fibers

Answer 11

recall, osteolysis and tibial insert failures when reinforced with UHMWPE
low shear strength causing fiber breakage and formation of harmful debris when carbon fibers in scaffolding device to induce tendon or ligament repair

Question 12

Polymer fibers

Answer 12

not comparably strong or stiff compared to other polymers (except aramid or UHMWPE), Aramid, polyethylene fibers, dacron, PLA/PGA. ceramics, glasses

Question 13

Aramid

Answer 13

aromatic polyamide fibers-genetic name
known as kevlar, nomex
lighter density than carbon, lower modulus, lower tensile strength
-resist impact and abrasion, absorb moisture, poor compressive strength

Question 14

Polyethylene fibers

Answer 14

good commercial products: UHMWPE

• high strength and modulus
• extensively used in medicine:
• meniscus bearing load of orthopedic implants, excellent biocompatibility
• reinforced acrylic resins 4 dentistry
• intervertebral disc prosthesis
• fabrication of ligament 4 augmentation devices

Question 15

Dacron

Answer 15

common name for polyethylene terephthalate fibers
Medical application:
-cardiovascular grafts
-proposed 4 orthopedic prostheses
-artificial tendons and ligaments
-intervertebral discs
Plastic surgery:
-blood vessels, breast implants

Question 16

Polylactic, polyglycolic acid and copolymers

Answer 16

biodegradable polymers, intramedullary biodegradable pin and matrix, ligament reconstruction, sutures, tissue engineering

Question 17

Ceramics

Answer 17

most biocompatible, weak tension or shear, brittle materials compared to metals
TCP and HA: bioceramics
orthopedic and dental for TCp

Question 18

Glasses

Answer 18

reinforced plastic matrices to form structural composites and molding compounds
Glass fiber plastic composite materials:
-high strength to weight ratio
-good dimensional stability
-good heat, cold, moisture, corrosion resistance
-good electrical insulation prop
-low cost
used to increase mechanical properties of acrylic resins 4 dentistry

Question 19

Matrix Systems Part I

Answer 19

• cutting tools, power gen. equipment, process industries, aerospace (all for metal and ceramic matrix)
• Calcium phosphate: bone cement

Most common matrices are synthetic non-absorbable polymers:

• UHMWPE
• Poly ether ether ketone (PEEK)
• Polysulfone, poly tetra fluoro ethylene
• Poly methyl methacrylate
• hydrogels

Question 20

Matrix Systems Part II

Answer 20

matrices reinforced with carbon fibers, polyethylene fibers, and ceramics:

• prosthetic hip stems
• fixation devices
• artificial joint bearing surface
• artificial tooth roots
• bone cements

other matrix materials:
poly glycolic acid
poly lactic acid
both used for sutures and impact materials for repair of various osseous and soft tissues