Dynamic fracture toughness of 6061Al composites reinforced with SiC particulates

<I>In-situ</I> Observations of Fracture Processes in 0.6 &mu;m and 9.5 &mu;m SiC<SUB>P</SUB>/6061Al Composites

“…(3) based on the CTODs at the maximum loading points, respectively for the coarse and fine particle reinforced composites as tabulated in Table 1. In our recent reports, 3,4) however, the fracture toughness measured according to the ASTM standard method 15) is lower for the coarse particle reinforced composite than that for the fine particle reinforced composite ( Table 1). The measured crack initiation toughness is 4.9 and 7.0 kJm À2 when the crack initiation point is determined by the ACP, and is 8.7 and 11.3 kJm À2 when the crack initiation point is determined by the maximum loading point, respectively for the coarse and fine particle reinforced composites.…”

“…3,4) The CTODs () measured for the two composites at the abrupt change points of compliance change rate (ACPs) and at the maximum loading points are summarized in Table 1. At the ACPs, the CTODs are about 8 and 4 mm for the composite reinforced with coarse SiC particles and for the composite reinforced with fine SiC particles, respectively.…”

“…[1][2][3][4] The degradation in fracture toughness is influenced by many factors, such as particle size, aspect ratio, volume fraction, distribution and strength of the particles, strength of the interface between the particles and matrix, and properties of their matrix alloys. [3][4][5][6][7][8] It has been recognized that an increase in volume fraction of SiC p leads to a decrease in fracture toughness of the composite, 3,[5][6][7] but an increase in SiC particle size causes an increase in fracture toughness. 8) In the previously reported work, 3,[5][6][7][8] the studied SiC particle sizes were larger than 2 mm.…”

“…[3][4][5][6][7][8] It has been recognized that an increase in volume fraction of SiC p leads to a decrease in fracture toughness of the composite, 3,[5][6][7] but an increase in SiC particle size causes an increase in fracture toughness. 8) In the previously reported work, 3,[5][6][7][8] the studied SiC particle sizes were larger than 2 mm. More recently, however, a result in our research 4) indicated that the fracture toughness (both crack initiation toughness and propagation toughness) of the composite reinforced with much finer SiC particles (0.6 mm) was obviously higher than that of the composite reinforced with coarse particles (9.5 mm) although the volume fraction of the reinforcements was kept the same.…”

“…[3][4][5][6][7][8][9] They found that the fracture modes in the SiC P /Al alloy composites mainly included the failure of their matrix, the fracture of interfaces between the particles and matrix, and the fracture of particles themselves. All their inspections, however, were made on the post-fractured specimens, therefore unable to disclose the detailed fracture processes during loading.…”