40TH ANNIVERSARY Figure 11 Photomicrographs of quenched surfaces of (90/0)3s Nicalon/CAS with crack patterns superimposed for ATs of(a)450C,(b)600C and(c) 800°C. be seen that PMCs accumulate at a much higher rate than tion matrix cracks of various orientations were identified HMCS as the main mode of damage In longitudinal plies these cracks propagated at right angles to the surface fibre length 3.2.3. Summary of observations whereas in transverse plies they ran along the length of of multi-layer cross-ply Nicalon/CAS the ply. As these matrix cracks were deflected upon en- laminates countering fibre-matrix interfaces, no fibre breaks could Damage modes due to thermal shock and their be detected in any ply even at the highest thermal shocks mulation with increasing shock severity in spec The critical quenching temperature difference was of two laminate configurations of multi-layer cross-ply found to be higher for the (90/0 )3s laminate. Damage in Nicalon/CAS CMCs were described in detail in this sec both laminates originated in the central, thick plies and 95940TH ANNIVERSARY Figure 11 Photomicrographs of quenched surfaces of (90/0)3s Nicalon/CAS with crack patterns superimposed for
Ts of (a) 450◦C, (b) 600◦C and (c) 800◦C. be seen that PMCs accumulate at a much higher rate than HMCs. 3.2.3. Summary of observations of multi-layer cross-ply Nicalon/CAS laminates Damage modes due to thermal shock and their accu￾mulation with increasing shock severity in specimens of two laminate configurations of multi-layer cross-ply Nicalon/CAS CMCs were described in detail in this sec￾tion. Matrix cracks of various orientations were identified as the main mode of damage. In longitudinal plies these cracks propagated at right angles to the surface fibre length whereas in transverse plies they ran along the length of the ply. As these matrix cracks were deflected upon en￾countering fibre-matrix interfaces, no fibre breaks could be detected in any ply even at the highest thermal shocks. The critical quenching temperature difference was found to be higher for the (90◦/0◦)3s laminate. Damage in both laminates originated in the central, thick plies and, 959