Influence of the Processes Parameters on the Properties of The ...

Chapter 4.
Experimental Procedures and Protocols for Analyses
(A)-Scaffold top slice view.
(B)-Scaffold right slice view.
(C)-Scaffold front slice view.
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(D)-Scaffold skeletal view.
Scaffold 95%PLGA+2.5%ATCP+2.5%TCP processed at P sat =100 bars, T sat =48 o C,
T sat =20 min, dP/dt= 3 bar/s
Figure 4.30: CT slice view from different direction for bone scaffold showing <strong>the</strong>
interconnectivity <strong>of</strong> pores
5 Mechanical Tests on Foams
5.1 Experimental Conditions <strong>of</strong> Test
Brazilian tests were conducted by Gerard Dechambre (CIRIMAT) on computerized universal
testing machine (Hounsfield H25KS). The compressive modulus E c and <strong>the</strong> compressive strength c are
easy to measure for foams by uni-axial compression tests.
A loading frame, 25kN capacity, having a base and a cross head joined toge<strong>the</strong>r with two solid
pillars with nuts. At <strong>the</strong> top, <strong>the</strong> pillars have long threads for height adjustment. On <strong>the</strong> base, a 25 kN
hydraulic jack is centrally fixed between <strong>the</strong> pillars. This jack has an integral pumping unit and oil reservoir.
A 25 kN capacity pressure gauge is fixed to <strong>the</strong> jack for indicating <strong>the</strong> load on <strong>the</strong> specimen.
Samples used in this investigation were discs <strong>of</strong> 10 mm diameter and 3 mm thickness. Tests were
performed at room temperature. Each sample was tested three times and <strong>the</strong> average value was incorporated.
The composite foams were cut into circular flat-bottom disks (10 mm in diameter) for mechanical testing.
The top layer <strong>of</strong> <strong>the</strong> disk was removed to achieve <strong>the</strong> desired thickness (3 mm) and ensure a flat surface.
Once <strong>the</strong> system calibrated/tared and <strong>the</strong> crosshead was in <strong>the</strong> correct position, samples were loaded and
were compressed in z – direction <strong>of</strong> scaffold fabrication process at cross speed <strong>of</strong> 0.5 mm/min between two
steel platens up to a strain level <strong>of</strong> approximately 75%.
5.2 Principle <strong>of</strong> Curve Analysis
The data was converted to Micros<strong>of</strong>t Excel format <strong>the</strong>n and <strong>the</strong> force-displacement data was
converted to stress-strain curves. Strain was determined from <strong>the</strong> values for displacement and <strong>the</strong> original
height <strong>of</strong> <strong>the</strong> scaffolds. Strain was determined from <strong>the</strong> values for displacement and <strong>the</strong> original height <strong>of</strong> <strong>the</strong>
scaffolds. The slope <strong>of</strong> <strong>the</strong> initial linear portion, elastic region, <strong>of</strong> <strong>the</strong> stress-strain curve was <strong>the</strong>n used to
determine <strong>the</strong> modulus. The compressive strength was estimated by determining <strong>the</strong> stress at an <strong>of</strong>fset <strong>of</strong> 1%