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为了能准确预测复合材料层合板的失效起始和破坏过程,发展了一种考虑层合板就地效应(In-situ Effect)的强度理论,方法包括就地强度的确定、失效起始判定和材料性能退化。介绍并推导了基于断裂力学假设的就地强度计算方法,将层合板内的铺层分为内嵌厚层、内嵌薄层和外表面层3种类型,不同类型的层分别对应不同的计算方法。建立了一种考虑就地强度的面内失效起始准则,提出了相应的强度分析方法流程。对单向和多向层合板的失效包线进行了预测,计算结果表明发展的强度理论能很好地预测结构的失效起始,充分反映材料从失效起始到最终破坏的试验现象和规律,与传统Hashin准则相比预测精度明显提高。通过对准各向同性层合板失效包线预测发现,在进行层合板强度分析时考虑就地强度能明显提高预测失效起始的准确性和精度,在复合材料结构强度分析过程中考虑层合板的就地效应十分必要。
In order to accurately predict the failure initiation and failure process of composite laminates, a theory of strength considering the In-situ Effect of Laminated Plates has been developed. The methods include the determination of in-situ strength, failure onset determination, Performance degradation. The in-situ strength calculation method based on the assumption of fracture mechanics is introduced and deduced. The plies in the laminate are divided into three types: thick embedded layer, embedded thin layer and external surface layer. Different types of layers correspond to different calculations method. A criterion of in-plane failure considering in-situ strength was established and the corresponding flow of intensity analysis method was proposed. The failure envelopes of unidirectional and multi-directional laminates are predicted. The calculated results show that the developed strength theory can well predict the onset of structural failure and fully reflect the experimental phenomena and laws of material failure from the initial failure to the final failure. Compared with the traditional Hashin criterion, the prediction accuracy is obviously improved. By predicting the failed envelope of an isotropic laminate, it is found that considering the in-situ strength during laminate strength analysis can significantly improve the accuracy and precision of predicting the onset of failure. In the process of composite structural strength analysis, Local effect is necessary.