Composites Flashcards
Composite
two or more chemically distinct parts with interface b/w, discontinuous phase within continuous
Discontinuous phase
harder, stronger, reinforcement material
Continuous phase
matrix
Desired mechanical properties
stiff, strong, tough, fatigue resistance
Fibrous composite
better mechanical effectiveness than particulate in terms of strength, stiffness
Particle reinforced composites
isotropic (same physical properties everywhere)
Failure of composite
increase chance of exposing fibers/particles to surrounding biological environment, separation of interface to matrix, stress exceeding interface strength, fatigue
Carbon fibers
lightweight, flexible, high strength, high elastic modules material, contain 93-95% carbon, graphite fiber = +99% carbon
Main reinforcing materials
carbon fibers, polymer fibers, ceramics, glasses
Carbon and graphite fibers
stiffer and stronger than steel
low density
poor shear strength
Negative effects of medical devices using carbon fibers
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
Polymer fibers
not comparably strong or stiff compared to other polymers (except aramid or UHMWPE), Aramid, polyethylene fibers, dacron, PLA/PGA. ceramics, glasses
Aramid
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
Polyethylene fibers
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
Dacron
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
Polylactic, polyglycolic acid and copolymers
biodegradable polymers, intramedullary biodegradable pin and matrix, ligament reconstruction, sutures, tissue engineering
Ceramics
most biocompatible, weak tension or shear, brittle materials compared to metals
TCP and HA: bioceramics
orthopedic and dental for TCp
Glasses
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
Matrix Systems Part I
- 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
Matrix Systems Part II
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
