Comparison of Failure Modes in 2-D and 3-D Woven Carbon Phenolic Systems

[摘要] NASA Ames Research Center is developing Woven Thermal Protection System (WTPS) materials as a new class of heatshields for entry vehicles (Stackpoole). Currently, there are few options for ablative entry heatshield materials, none of which is ideally suited to the planetary probe missions currently of interest to NASA. While carbon phenolic was successfully used for the missions Pioneer Venus and Galileo (to Jupiter), the heritage constituents are no longer available. An alternate carbon phenolic would need to be qualified for probe missions, which is most efficient at heat fluxes greater than those currently of interest. Additional TPS materials such as Avcoat and PICA are not sufficiently robust for the heat fluxes required. As a result, there is a large TPS gap between the materials efficient at very high conditions (carbon phenolic) and those that are effective at low-moderate conditions (all others). Development of 3D Woven TPS is intended to fill this gap, targeting mid-density weaves that could with withstand mid-range heat fluxes between 1100 W/sq cm and 8000 W/sq cm (Venkatapathy (2012). Preliminary experimental studies have been performed to show the feasibility of WTPS as a future mid-range TPS material. One study performed in the mARC Jet Facility at NASA Ames Research Center characterized the performance of a 3D Woven TPS sample and compared it to 2D carbon phenolic samples at ply angles of 0deg, 23.5deg, and 90deg. Each sample contained similar compositions of phenolic and carbon fiber volume fractions for experimental consistency. The goal of this study was to compare the performance of the TPS materials by evaluating resulting recession and failure modes. After exposing both samples to similar heat flux and pressure conditions, the 2D carbon phenolic laminate was shown to experience significant delamination between layers and further pocketing underneath separated layers. The 3D Woven TPS sample did not experience the delamination or pocketing failure modes because z-fibers in the through-thickness direction provided extra reinforcement to hold material layers together. Therefore, the benefit of using a 3D weave architecture was shown to alleviate failure modes experienced by a 2D laminate sample of similar material composition. In summary this poster reviews the thermal response performance comparisons drawn between a 3D Woven TPS sample and 2D Carbon Phenolic samples after performing rigorous heating experiments in the mARC facility at NASA Ames. Although the mARC Facility is still in its developmental stages, researchers expect similar trends in failure modes observed from large scale arc jet facilities. This work helps demonstrate the viability of 3D Woven TPSs as a new TPS option for future atmospheric entry missions.

[发布日期] 2013-06-17

[学科分类] 复合材料