Development of Numerical Constitutive Models for Carbon-Carbon Composites

Abstract

ObjectivePredict the stiffness and strength of oxidation-resistant carbon-carbon subjected to thermal and mechanical loads in an oxidizing environment Status of effortA three-dimensional progressive failure analysis of carbon-carbon composites was developed. To facilitate the study, various mesh generators and graphical pre-and postprocessing tools were developed. These tools were used to study carbon-carbon during cooldown from processing temperature and subsequent mechanical loads. This grant was tightly integrated with the AASERT grant F49620-93-1-0471, which ended last year. The student supported under the AASERT grant, Clint Chapman, has graduated (and is employed) with a Ph.D. This final year of the subject grant has been invested in documenting our efforts in the open literature and assembling documentation for the tools developed by Dr. Chapman so they could be used in subsequent projects. AccomplishmentsTwo of the biggest challenges in the analysis of textile composites is developing a valid 3D finite element mesh and deriving boundary conditions for the smallest possible analysis region (since the computational challenge is inherently high). We can now obtain meshes and boundary conditions for plain and 8 harness satin weaves with a wide range of waviness, tow cross-section, and mesh refinement. Only a few parameters have to be specified.. .the rest is automatic. We have also enhanced our visualization programs and associated utilities so that it is much more convenient to examine stress and strain distributions, deformed geometries, damage distribution, and differences between models.We have continued to document our efforts in the literature. The results of our simulations were presented at ICCE/5 in July, 1998. A journal paper describing the simulations is almost complete. The title is "Thermally Induced Damage Initiation and Growth in CarbonCarbon Composites. AGENCY USE ONLY (Leave blank)2. REPORT DATE 3. REPOR", AFRL-SR-BL-TR-OO- ABSTRACT {Maximum 200 words)A three-dimensional progressive failure analysis of carbon-carbon composites was developed. To facilitate the study, various mesh generators and graphical pre-and post-processing tools were developed. These tools were used to study carbon-carbon during cool-down from processing temperature and subsequent mechanical loads. This grant was tightly integrated with the AASERT grant F49620-93-1-0471, which ended last year. The student supported under the AASERT grant, Clint Chapman, has graduated (and is employed) with a Ph.D. This final year of the subject grant has been invested in documenting our efforts in the open literature and assembling documentation for the tools developed by Dr. Champan so they could be used in subsequent projects. XiaodongTang Abstract Efficient 3D analysis of periodic structures depends on identifying the smallest region to be modeled and the appropriate boundary conditions. This paper describes systematic procedures for deriving the boundary conditions for general periodic structures. These procedures are then used to ...