INTRODUCTION TO PROCESSING OF BIOMATERIALS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 250

8.3.4 Biocomposites
8.3.4.1 Introduction. Metals, ceramics and polymers when used indepen-
dently as biomaterials can have certain limitations. Hence, the search for an ideal
biomaterial led to the development of biocomposites that are materials made
up of physical combinations of conventional materials. Biocomposites generally
consist of two phases, a matrix (base) phase in which there is an embedded re-
inforcing phase that is normally made up of particles or fi bers [49] and hence
in the fi nal composite material both phases remain separate at the macro scale.
Tailoring of composition and structure of both phases can be done to obtain spe-
cifi c physicomechanical properties and hence desired biological response. Thus
the composition, synthesis and processing of biocomposites are aspects that must
be carefully considered while designing a composite for biomedical applications.
8.3.4.2 Classifi cation. Though composites can be classifi ed in various
ways, depending on the type of reinforcing phase they can be classifi ed as follows:
[1, 44, 50 - 53]
• Fiber Reinforced
Continuous fi ber reinforced (long fi bers extending throughout matrix
phase) Alignment of long fi bers gives anisotropy to the properties of fi nal
composite.
Discontinuous fi ber reinforced (short fi bers dispersed in matrix phase)
Random orientation of short fi bers gives isotropy to the properties of
fi nal composite.
• Particle Reinforced [54]
Small particles or whiskers dispersed throughout the matrix phase.
8.3.4.3 Manufacturing
8.3.4.3.1 FIBER/PARTICLE REINFORCED COMPOSITES [1, 44] . In general, the
procedure for fabrication of composites involves reinforcing and matrix phase
mixing, compaction and consolidation. However, the manufacturing technique
can vary with fi nal biocomposite composition. For example, composites that use
thermoplastic materials as the continuous phase or need to be resistant to water
intrusion are not fabricated by open mold processes [1]. Figure 8.5 provides a sche-
matic of the processing techniques used for fi ber/particle reinforced composites.
Curing (cross linking of matrix phase material) may be used in situ or post
fabrication to reduce degradation and increase strength. Depending on the type
of composite material, curing may be induced by light, heat, electron beam or
x - ray.
8.3.4.3.2 METAL MATRIX COMPOSITES [52, 55 - 57] . Though Metal Matrix
Composites (MMCs) are classifi ed under fi ber or particle reinforced composites,