Aerospace composites mechanical damage prediction through multi-scale modelling

20世纪60年代，复合材料的引入取代了金属航空部件，为轻型飞机提供了希望。更轻的飞机消耗更少的燃料，这为飞机制造商提供了竞争优势，并减少了污染排放，这对确保地球的可持续性至关重要。然而，加拿大飞机的减重幅度在0 - 5%之间，而资深航空复合材料专家认为，如果使用新型复合材料，减重幅度可能在15%左右，甚至更高。过于昂贵的认证成本和过于保守的安全因素导致了这种糟糕的性能。这种情况必须得到纠正，以保持加拿大在航空航天领域的竞争力。***准确的复合材料预测损伤模型可以大大减少复合材料部件的重量，因为：i)一些认证测试可以用预测取代，这将加速引入性能更好的新材料；ii)准确的模型将降低安全系数，从而使飞机更轻。世界范围内的复合材料失效试验表明，目前的模型无法在合理的精度范围内预测每种载荷情况下的复合材料失效。复合材料的损伤是一个复杂的过程，由亚微米裂纹开始，并在尺度层次上传播。经典连续介质力学不适用于处理这些不连续性。***提出的研究计划旨在通过同时研究：i)识别相关材料参数的实验方法，ii)预测复合材料损伤开始和传播的模型，以及iii)提供有效的复合材料损伤预测的数值策略，开发预测复合材料失效的多尺度框架。该程序依赖于周动力学，这是一个相对较新的连续介质力学公式，避开了大多数经典方法的缺点。***本研究将由4名博士生和1名博士后参与，13名本科生和1名副研究员支持。大多数研究生将由具有互补专业知识（实验、理论和数值）的教授共同指导。每位博士生将与国际知名专家进行短期（2-3周）的实习，并在航空航天公司进行为期4个月的实习，这是一个旨在提高研究生航空航天行业准备水平的更大培训计划的一部分。***该计划将引发基本的范式转变，以正确解决复合材料损伤预测问题，从而获得复合材料提供的全部减重潜力。该方法是为航空航天工业量身定制的，以加速其与下一代专家的转移，这些专家将在整个项目中为此目标进行专门培训。*** *** *** **

The replacement of metallic aerospace parts by the introduction of composites in the 1960's offered the promises of lighter aircraft. Lighter aircraft consume less fuel, which provides a competitive advantage to aircraft manufacturers, and reduce polluting emanations, which is essential to ensure Earth's sustainability. Yet, weight savings in Canadian aircraft range from 0 to 5%, whereas senior aerospace composites experts believe that it could safely be around 15%, and beyond with new composites. Prohibitively expensive certification costs and over-conservative safety factors contribute to this poor performance. This situation must absolutely be remedied to maintain Canada's competitiveness in aerospace.***Accurate composites predictive damage models could significantly decrease the weight of composite parts, since: i) some certification tests could be replaced by predictions, which would accelerate the introduction newer materials of improved performance and ii) accurate models will lead to lower safety factors, and hence, to lighter aircraft. The World Wide Failure Exercise on composites revealed that current models cannot predict composite failure within reasonable accuracy for every load case. Composites damage is a complex process initiated by sub-micron cracks that propagate through the hierarchy of scales. Classical continuum mechanic is ill-suited for handling these discontinuities. ***The proposed research program aims at developing a multi-scale framework for predicting composites failure by simultaneously investigating: i) experimental methods for identifying relevant material parameters, ii) models for predicting composites damage initiation and propagation and iii) numerical strategies for delivering efficient composites damage predictions. The program relies on Peridynamics, which is a relatively new formulation for continuum mechanics that eludes most of the classical approaches' shortcomings. ***The research will be carried out by 4 PhD students and 1 post-doctoral fellow, supported by 13 undergraduate students and 1 research associate. Most graduate students will be co-supervised by professors of complementary expertise (experimental, theoretical and numerical). Every PhD student will perform a short-time (2-3 weeks) internship with well-known international experts, as well as a four-month internship in an aerospace company as part of a larger training program aiming at improving the aerospace industry readinyness level of graduate students.***This program should trigger the essential paradigm shift for properly addressing composites damage prediction, and hence reap the full weight reduction potential composites offer. The methodology is tailored for the aerospace industry to accelerate its transfer with the next generation of experts that will be specifically trained for that objective throughout the program. *** *** *** **