Evaluation Algorithm Research On Residual Strength Of Open-hole Composite Laminates Based On Bayesian Theories

So rapid as science and technology develops in modern society,carbon fiber reinforced composites has gradually become one of the most important materials in aviation and aerospace fields,and been playing an increasingly significant role in all domains.The first appliance of composites in aircraft appeared in minor part of its structures,and now,it becomes a popular choice in main bearing part.Structures in aircraft is too sophisticated to put wiring and maintenance into first consideration,which leads to open-hole designs that cannot be avoided.As it is well acknowledged,for the sake of the phenomenon of stress concentration take place around holes under loads,open-hole design will considerably weaken the strength of the composite structures that bears.Therefore,it is necessary to conduct a systematic process upon the assessment of residual strength of the open-hole structures.Besides,open-hole structures,that made in composites,will inevitably confront with the property distribution of materials,which leads to a prerequisite assessment to its security and reliability.Thus,assessments to reliability,residual strength and damage tolerance of composite structures are of major tasks.Assessment to residual strength of open-hole composite laminates is the most important part of its mechanical property analysis.Majority of conventional assessment processes paid too much attention on the relationship between open-hole size and residual strength,and failed to focus on distribution of residual strength.Some,of course the minority ones,studied its distributions on a specific open-hole size,which lacked the universality to general problems.Under these circumstances,when reliability assessments to residual strength of open-hole composite laminates are necessary in practical engineering,solutions often depend on specific conditions.In order to satisfy the demand of domestic aviation industry,the dissertation,by correctly understanding the current situation and technology at home and deliberately researching among various reliability assessment technologies in abroad,is here to present an innovative evaluation algorithm on residual strength of composite laminates,which combines assessment to relationship between residual strength and open-hole size and analysis of residual strength distribution composite structures.Taking the curve that fit by residual-strength-FEM-results of different open-hole sizes as base of analysis,the algorithm draws a comprehensive assessment process on residual strength of open-hole composite laminates with limited datum.It brings up a relationship between distribution of residual strength and open-hole size,and a function of critical residual strength value of any percentage depends open-hole size with Bayesian theories and Markov Chain-Monte Carlo Methods,so as to provide fair evidence strength design and reliability assessment of composite structures in qualitatively and quantitatively ways,respectively.Evaluation algorithm research on residual strength of composite structures is fundamental for reliability analysis of bearing part in aircraft and yields further studies.Not until residual strength of open-hole composite structures was successfully evaluated,can the further probabilistic analysis such as safety,reliability and damage tolerance be achieved and guaranteed,and strength design on composite structures be reasonably and comprehensively navigated.