D.-H. Kuo, W.M. Kriven/ Materials Science and Engineering A210(1996)123-134 z30 Alo, Fiber/Lapo, Coating/Alo, Matr 10 0 L,,,L,A,,L,,,,L, Crosshead Displacement(um Coating/A°3 合m出Hh=m Crosshead Displacement( um) Fig. 15. Load vs. crosshead displacement curves of fiber pushout tests for Al2O, fiber/ LaPO4 coating/Al,O, matrix(a)and Y,Al O12 fiber/ LaPOa coating/ Al,, matrix(b)model systems between the components is not strong. In this study, the LP/LA, laminate undergoes inte Fig. 14. Scanning electron micrographs of the fiber/coating interface facial delamination and the interfacial bonding between region for Al2O3 fiber/ LaPO. coating/Al2O3 matrix(a)and Y3AlsO, iber/LaPO, coating/Al,O3 matrix(b) model systems firing and annealing. These observations result from the “128g chemical compatibility and small mi smatch in the Ctes between the components of the laminates. The CTE of 2 monazite-type LP is9.6×10-6℃C-1(20-1000133 Linear FEng which is close to 8.8 x 10-6 oC-I of A12O3[25]and 8.0 x 10-6C- of YAG [26]. In comparison, the CTE 1o, ber/LAPo, coating/Al, matrix Coating Thickness: 6 um of Lau was measured in this study to be 100x 10-6 °C-1(200-1000°C Embedded Fiber Length, L(mm) 4.3. Mechanical evaluation of laminated composites 60 Model Fitting Whether or not delamination occurs in laminates τ,100M luring testing is decided by complex factors, such as the chemical bonding, thermal and mechanical proper- ties of the laminae, the testing methods used and the relative thicknesses of the laminae. Although laminates YAG,/LPO, /Alo can be used for interfacial study, a laminated composite with a weak interface may not show delamination easily by indentation and flexural tests. This complexity also Embedded Fiber Length, L occurred in the work of LP/A laminates [13], where Fig. 16. Variation of the peak load (Po) as a function of the delamination occurred within thicker layers, but not within thinner layers. However, if a laminate shows embedded fiber length(L)in fiber pushout tests of Al2O, fiber/ LaPO coating/Al2O3 matrix (a) and Y3Als O,, fiber/ LaPO4 coating/AlO delamination, it suggests that the interfacial bonding matrix(b)model systemsD.-H. Kuo, W.M. Kriven / Materials Science and Engineering A210 (1996) 123-134 131 5O 4O A z 3o 10 0 50 ' ' ' ' I ' ' ' ' I " ' ' ' I .... I ' ' ' ' (a) P = 36.5 N P F.mbedded Hber ~ O~ mm 10 20 30 40 Crosshead Displacement lima) 50 ' ' ° ' I " ' ' ' ' ' ' ' I .... I ' ' " ' (b) P :' 4o.5 N 40 P 4 Coating / ~d20 ~ Matrix 10 / A~ C~I~ Thicka~!~: - 9 itm ~b~ld~ l~,un~t Length: 0.8 =w~ 0 10 20 30 40 50 Crosshead Displacement (~xm) Fig. 15. Load vs. crosshead displacement curves of fiber pushout tests for AI203 fiber/LaPO4 coating/Al203 matrix (a) and Y3A15OI2 fiber/ LaPO4 coating/Al203 matrix (b) model systems. Fig. 14. Scanning electron micrographs of the fiber/coating interface region for AI203 fiber/LaPO4 coating/A1203 matrix (a) and Y3AIsOt2 fiber/LaPO4 coating/A1203 matrix (b) model systems. firing and annealing. These observations result from the chemical compatibility and small mismatch in the CTEs between the components of the laminates. The CTE of monazite-type LP is 9.6 x 10- 6 °C-1 (20-1000 °C) [13] which is close to 8.8 x l0 -6 °C-1 of A1203 [25] and 8.0 × 10 -6 °C- 1 of YAG [26]. In comparison, the CTE of LA~I was measured in this study to be 10.0 × 10 6 o C 1 (200-1000 °C). 4.3. Mechanical evaluation of laminated composites Whether or not delamination occurs in laminates during testing is decided by complex factors, such as the chemical bonding, thermal and mechanical proper￾ties of the laminae, the testing methods used and the relative thicknesses of the laminae. Although laminates can be used for interfacial study, a laminated composite with a weak interface may not show delamination easily by indentation and flexural tests. This complexity also occurred in the work of LP/A laminates [13], where delamination occurred within thicker layers, but not within thinner layers. However, if a laminate shows delamination, it suggests that the interfacial bonding between the components is not strong. In this study, the LP/LAll laminate undergoes inter￾facial delamination and the interfacial bonding between 70 (a) 6O Sheaur-l~ Model Pitting i 50 ~d "~n~ ~~ g ¢~" 30 ~ ~d = 128 l~gpa 2O o .... ," • o~. 0.4 0.6 o~ ~ a.~ F.~bedded ~ ~ L (-,~) 6O ' " " I " ' ' I = ' " lH.i~a. ~ ' I " " ' I " " " 0 o o.2 0.4 0.6 o.s a ~.2 F.adx.dded ~ ~ L (ram) Fig. 16. Variation of the peak load (Pp) as a function of the embedded fiber length (L) in fiber pushout tests of AI203 fiber/LaPO 4 coating/Al203 matrix (a) and Y3AIsOl~ fiber/LaPO4 coating/Al203 matrix (b) model systems