Investigation of Internal Cracks in Epoxy-Alumina Using In Situ Mechanical Testing Coupled with Micro-CT

Polymer-ceramic composites are widely used in biomedical applications. This paper presents the results of an experimental investigation on the crack extension inside epoxy-alumina. Specimens with 5 vol.%, 10 vol.%, …, 25 vol.% fillers fractions were fabricated. Three-point bending on single-edge notched bend specimens were performed using conventional mechanical tester and in situ mechanical tester coupled with micro-CT, respectively. Fracture toughness was measured to be 2.10–2.51 MPam, and it decreased with increasing filler fraction. When cracks were shorter than 0.88 mm, crack resistance for 5 and 25 vol.% epoxy-alumina was similar. Beyond 0.88 mm, 25 vol.% epoxy-alumina exhibited no crack resistance, whereas stress intensity factor kept increasing in 5 vol.% epoxy-alumina. The matrix-particle interfaces were the weakest link, where cracks often initiated from. Crack bridging by uncracked ligament and crack deflection were commonly observed toughening mechanisms. To design robust epoxy-alumina composites, increasing matrix-particle interface strength is recommended for future work.