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SYNOPSISThe effect of the solvent 1-methyl-2-pyrrolidinone ( N M P ) on the curing of polyimide resins synthesized from pyromellitic dianhydride ( PMDA) and 4,4'-oxydianiline (ODA) has been investigated. Three polyimide precursors, i.e., the polyamic acid ( PAA) , with ond step involves the dehydrative cyclization of the PAA ( imidization ) to give rise to the polyimide (PI).This description fails to disclose the complexity and specific features of the two-step method. Important factors that affect the ultimate properties of a polyimide resin may include the nature of solvent-PAA interaction, the imidization reaction, and the side reactions accompanying these processes such as the reversible anhydride formation.The solvent-PAA interaction has been well established by various author^.^-^ Worthy of note is the study of a low-molecular-weight polyimide model compound by Brekner and Feger.3 They revealed the existence of 4 / 1 and 2 / 1 molar complexes between the solvent 1-methyl-2-pyrrolidinone ( N M P ) and the diamic acid synthesized from pyromellitic

Vibration-damping behavior of unidirectional and symmetric angle-ply carbon fiber-epoxy laminates as well as their interleaved counterparts with a layer of poly(ethylene-co-acrylic acid) (PEAA) at the mid-plane was examined. The introduction of the PEAA layer significantly improved the damping capability. The effectiveness of interleaving increased with the flexural modulus of the outer layers. In the case of unidirectional laminates, calculations based on a sandwich structure of isotropic layers quantitatively reproduced this trend. In the case of angle-ply laminates, however, the model predicted only part of the improvement experimentally observed. This was explained in terms of the bending of the angle-ply laminates in the transverse direction which would induce additional deformations in the interleaf layer and was not accounted for by the present model.