The variation of ultimate tensile strength of unidirectional B/Al composites with test temperature is shown in Figure 131. 36,179,186,190 For comparative purposes, the variation of tensile strength with temperature for 6061 aluminum is also shown. The most important observation is that the composites retain their strength exceptionally well up to about 600°F (315°C). At 600°F (315°C) the composite tensile strengths are still 10 to 30 times higher than the tensile strength of the aluminum alloy matrix. The variation of ultimate tensile strength of cross- and angle-ply B/Al composites is shown in Figure 132. 179,186 Notice that the ±5° angle-ply and 0° to 90° cross-ply composites have the same temperature dependence as the unidirectional composites shown in Figure 131 while the ±30° angle-ply composites reflect the decreasing matrix strength above 300°F (149°C). The 0° to 90° cross-ply composites are being tested parallel to one half of their filaments so that this temperature dependence would be expected. The ±5° angle-ply composites have the same temperature dependence because they are less sensitive to matrix shear strength and because, for short gage lengths, a majority of the filaments extend from grip-to-grip. In comparison, extensive load transfer through the matrix is required for the ±30° angle-ply composites which is reflected in their stronger temperature dependence.