Interdisciplinary Design for Composite Coiled Tubulars: Effects of Viscoelasticity

This proposal is submitted for support of work which is Dr. Schapery's part of a collaborative effort by Drs. Ochoa, Whitcomb, Kinra and Schapery. The overall effort is described in the proposal of the same main title as above submitted by Drs. Ochoa and Whitcomb. Therefore, the Objective and Benefits for the project will not be repeated here. Other components of the proposal, Approach, Project Plan, etc., are covered here for only Dr. Schapery's portion of the effort. Dr. Kinra's proposal is concerned with damage detection and is entitled Ultrasonic NDE of Spoolable Tubulars.

APPROACH: Experimental and theoretical work will be done to develop explicit models for effects of viscoelasticity and time-dependent damage on response of composite coiled tubulars. Constitutive and damage growth models developed on earlier OTRC projects will be applied to the coiled tubular problem using specific material parameters for the composites and constituent materials selected for this new project. Additionally, simplified efficient methods for analytical/numerical viscoelastic stress and damage analysis will be developed in support of preliminary and advanced design analyses.

ANTICIPATED PROJECT DURATION: Three years

PROJECT PLAN FOR 1 (1999/2000):
Develop experimental test plan to characterize viscoelastic behavior and damage initiation and growth. Initiate testing of resin and composite coupons to characterize basic linear and nonlinear viscoelastic behavior. Formulate the existing general constitutive and damage models in forms that are appropriate and convenient for identification of material parameters using experimental results and for implementation in finite element analyses of coiled tubulars.

PROJECT PLAN FOR 2:
Complete experimental work on short-term viscoelastic material characterization. Initiate experimental program to check and refine (as necessary) material model for ability to predict local deformation and damage response to selected simulated loading and environments for coiled tubulars. Included will be initiation of a study to evaluate ability of the model to predict long-time performance (as permitted by the duration of this project) from short-term laboratory tests.

In collaboration with the other P.I.'s, (i) incorporate refined material model into finite element model of coiled tubulars, (ii) develop tube testing plan for evaluation of accuracy of structural model in predicting time-dependent tube response to realistic simulations of tube loading and environment, and (iii) identify the primary mechanisms from three-dimensional models and identify other simplifications that are to be incorporated within a practical analytical design tool.

PROJECT PLAN FOR 3:
In collaboration with the other P.I.'s (i) conduct tube tests to evaluate and refine (as necessary) capability of structural analysis model in predicting tube response as a function of time from short-time properties and (ii) evaluate importance of viscoelastic effects for coiled tubulars, including study of possible benefits of viscoelasticity in alleviating microcracking using, for example, selective heating during spooling and unspooling.

PRINCIPAL INVESTIGATORS: R. Schapery, O. Ochoa, J. Whitcomb, V. Kinra