R Boccaccini et al./ Composites Science and Technology 65(2005 )325-333 2 cm Fig. 6. Typical fracture surface of the composite investigated showing quantitatively correlate pull-out behaviour with the neasured Kl dat 3. 2. Ballistic impact resistance and damage Mullite fibre reinforced-mullite matrix composites, projectile impacts, demonstrated a 2 cm typical composite behaviour with the sample remaining in one piece despite some substantial localised damage, especially for high impact energy. Fig. 7(a) shows the macroscopic damage caused by a projectile having im- after ballistic test at: (a) low impact energy (4.2 J)and (b) high impa pact energy of 4.2 J wherein a considerable number of energy(30.1 J) fibres pulling-out on the rear face of the sample can be seen. Owing to the relatively low impact energy, the sample was not penetrated during this impact. Impact ing at higher velocities however led to penetration of the projectile through the samples causing failure as for example shown in Fig. 7(b) for a sample impacted with a projectile of 30.1 J energy. The sample stayed in one piece due to the presence of the fibres. Due to 20.15 he complex nature of the ceramic composite micro- structure(see Fig. 1), post-impact microscopic examina tion of the impacted surface did not reveal much structural detail. In the first instance however it seemed that the structural damage was highly localised around 005 In order to assess the effects of ballistic impact energy on microstructural damage and on structural integrity of the composite, the damaged samples were subjected Displacement(mm) placement curves for as-received and impact damaged Fig 8 Load-displacement curves for: (a)as-received and samples(impact energy 10. 35 J). As mentioned above, under investigation does not 心 the impression left by the ballistic impact was in the cen tre of the sample. As expected, the composite under investigation does not fail catastrophically, even after having been substantially damaged by the impact of of the projectile). This behaviour is in agreement with projectiles. Instead, the material retains its load bearing literature reports [30] on continuous fibre reinforced capacity after the commencement of failure(penetration glass-ceramic matrix composites. Fig 9 documents thequantitatively correlate pull-out behaviour with the measured KIc data. 3.2. Ballistic impact resistance and damage Mullite fibre reinforced–mullite matrix composites, when subjected to projectile impacts, demonstrated a typical composite behaviour with the sample remaining in one piece despite some substantial localised damage, especially for high impact energy. Fig. 7(a) shows the macroscopic damage caused by a projectile having im￾pact energy of 4.2 J wherein a considerable number of fibres pulling-out on the rear face of the sample can be seen. Owing to the relatively low impact energy, the sample was not penetrated during this impact. Impact￾ing at higher velocities however led to penetration of the projectile through the samples causing failure as for example shown in Fig. 7(b) for a sample impacted with a projectile of 30.1 J energy. The sample stayed in one piece due to the presence of the fibres. Due to the complex nature of the ceramic composite micro￾structure (see Fig. 1), post-impact microscopic examina￾tion of the impacted surface did not reveal much structural detail. In the first instance however it seemed that the structural damage was highly localised around the point of impact. In order to assess the effects of ballistic impact energy on microstructural damage and on structural integrity of the composite, the damaged samples were subjected to 4-point flexural strength test. Fig. 8 shows load–dis￾placement curves for as-received and impact damaged samples (impact energy 10.35 J). As mentioned above, the impression left by the ballistic impact was in the cen￾tre of the sample. As expected, the composite under investigation does not fail catastrophically, even after having been substantially damaged by the impact of projectiles. Instead, the material retains its load bearing capacity after the commencement of failure (penetration of the projectile). This behaviour is in agreement with literature reports [30] on continuous fibre reinforced glass–ceramic matrix composites. Fig. 9 documents the Fig. 6. Typical fracture surface of the composite investigated showing extensive fibre pull-out. Fig. 7. Macrographs showing the macroscopic composite damage after ballistic test at: (a) low impact energy (4.2 J) and (b) high impact energy (30.1 J). Fig. 8. Load–displacement curves for: (a) as-received and (b) impact damaged samples in 4-point flexural strength tests. The composite under investigation does not fail catastrophically, even after having been substantially damaged by the impact of projectiles. 330 A.R. Boccaccini et al. / Composites Science and Technology 65 (2005) 325–333