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Elastic moduli of a liquid crystalline polymer and its in ‐ situ composites
Author(s) -
Choy C. L.,
Lau K. W. E.,
Wong Y. W.,
Yee A. F.
Publication year - 1996
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.10519
Subject(s) - materials science , polycarbonate , composite material , elastic modulus , modulus , coupling (piping) , moduli , polymer , transverse plane , shear modulus , reinforcement , structural engineering , physics , quantum mechanics , engineering
The elastic moduli of a liquid crystalline polyesteramide (LCP) and polycarbonate/LCP in ‐ situ composites with 10 to 80 wt% of LCP have been measured as functions of draw ratio λ from 1 to 15 by an ultrasonic method. For the LCP, the sharp rise of the axial Young's modulus E 3 and the slight decreases of the transverse Young's modulus E 1 and the axial ( C 44 ) and transverse ( C 66 ) shear modulus with increasing λ result from the alignment of chains along the draw direction. E 1 , C 44 , and C 66 follow the lower bounds calculated using the series coupling scheme of the aggregate model. Although E 3 lies close to the lower bound at low λ, it follows the upper bound calculated according to the parallel coupling scheme at λ > 3. The elastic moduli of the composites have similar draw ratio dependences as those of the LCP. The strong increase in E 3 with increasing λ arises from the higher aspect ratio of the LCP domains in the composites and the improved molecular orientation within the domains. The reinforcement effect on the other moduli is much weaker, with E 1 and C 44 of the composites only 5 to 30% higher than those of polycarbonate at λ = 15. Since C 66 of the LCP decreases to a value below that of polycarbonate at λ > 2, there is a positive reinforcement effect at low λ but a negative effect at high λ.