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A model for time-independent and time-dependent damage evolution and their influence on creep of multidirectional polymer composite laminates.

机译：与时间无关和与时间有关的损伤演化模型及其对多向聚合物复合材料层压板蠕变的影响。

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摘要

Application of polymer matrix composites in engineering structures has been steadily increasing over the past five decades. Multidirectional polymer composites are one class of continuous fiber reinforced polymer matrix composites used in aerospace structures, where the desired mechanical performance outweighs the cost. Their modulus and strength degrade with time (known as creep and creep rupture) during the service, owing to the viscos-elasticity of the polymer matrix. Additional contribution to this degradation comes from various damage modes developed in the plies of the composite with time and identified in this thesis as TDD (Time Dependent Damage). These damage modes may also develop due to process-induced residual stresses, and during loading to the service load, identified as TID (Time Independent Damage). TID influences the TDD, the creep and the creep rupture. The objective of this thesis is to develop a model to predict the evolution of TID and TDD in multiple plies of a laminate and their influence on creep. The predominant damage mode, transverse cracking, is modeled in this study. The model consists of four modules, PIS, QSL, SL, and VA. The PIS, QSL, and SL moduli predict changes in ply stresses for incremental change in temperature, stress, and time respectively, using lamination theory and assuming linear elastic behavior of the plies during an incremental step. In parallel, each module predicts the stored elastic energy in each ply after each incremental step and compares it with a critical stored elastic energy criterion to determine if a ply would crack. If fracture is predicted, the VA module based on variational analysis, is invoked to determine the crack density and the perturbation in ply stresses due to cracking. The perturbation stresses are used by the module that invoked the VA module to determine the ply stresses after cracking during the current incremental step. The model predictions for a [+/-45/90]s laminate, at two test temperatures (80°C and 180°C) and four stresses in the range of 20--54 MPa, compare very well with experimental results validating the model.
机译：在过去的五十年中，聚合物基复合材料在工程结构中的应用稳步增长。多向聚合物复合材料是用于航空航天结构的一类连续纤维增强聚合物基复合材料，其中所需的机械性能超过了成本。由于聚合物基体的粘弹性，它们的模量和强度在使用过程中会随时间降低（称为蠕变和蠕变断裂）。对这种降解的进一步贡献来自复合材料层中随时间变化形成的各种损伤模式，在本文中被确定为TDD（时间相关损伤）。这些损坏模式也可能由于过程引起的残余应力而产生，并且在加载到服务负载期间被标识为TID（与时间无关的损坏）。 TID影响TDD，蠕变和蠕变断裂。本文的目的是开发一个模型来预测多层层压板中TID和TDD的演变及其对蠕变的影响。在这项研究中，主要的破坏模式是横向裂纹。该模型由PIS，QSL，SL和VA四个模块组成。 PIS，QSL和SL模量分别使用层合理论并假设在增量步骤中层的线性弹性行为，分别预测层应力随温度，应力和时间的增量变化而变化。并行地，每个模块在每个增量步骤之后预测每个层中的存储弹性能，并将其与临界存储弹性能标准进行比较，以确定层是否会破裂。如果预测到断裂，则调用基于变分分析的VA模块来确定裂纹密度和由裂纹引起的层板应力扰动。扰动应力由调用VA模块的模块使用，以确定在当前增量步骤中开裂后的板层应力。 [+/- 45/90] s层压板在两个测试温度（80°C和180°C）和四个应力在20--54 MPa范围内的模型预测，与验证模型。

著录项

  • 作者

    Asadi, Amir.;

  • 作者单位

    University of Manitoba (Canada).;

  • 授予单位 University of Manitoba (Canada).;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 291 p.
  • 总页数 291
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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