Material selection brittle behavior

In order to evaluate the contraction behavior of the candidate liner material when coupled to a laminate composite, a simple immersion test was performed on selected samples. The specimens were immersed in a liquid-hydrogen bath for 45 min upon removal they were subjected to a qualitative examination, for cracks, color change, etc. All films tested reacted favorably except the aluminized Mylar, which developed cracks in the aluminum upon flexing, and Kynar, which was very brittle and cracked without external load. Contraction properties of various materials are shown in Fig. 3. 

Otherwise, the safety coefficients are not selected only on the basis of stress load type, form and processing conditions, but also depend on the plastic material itself. A notch-sensitive plastic that is hard and brittle requires higher safety coefficients than one that is hard and tenacious. Within this framework, the semicrystalline thermoplastics generally show a more favorable behavior than the amorphous ones. 

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