Fatigue behaviour and life prediction of filament wound CFRP pipes based on coupon tests

This paper investigates the fatigue behaviour of filament wound Toray T700/Epotech X4201 composite pipes with different lay-ups. The present work compares the fatigue behaviour of coupon specimens manufactured with two different fiber orientations under tension-tension and tension-compression cyclic actions. The test results show that the lay-up and stress ratio have significant effect on the failure mechanism and fatigue life of carbon fiber reinforced polymer (CFRP) composite coupons. This paper develops an empirical model, which integrates the effect of stress ratio in a fatigue damage parameter, to evaluate the fatigue life of the CFRP filament wound coupons. Combined with the numerically calculated stresses at the critical locations corresponding to the fatigue damage locations, the proposed empirical model developed from the coupon test database predicts successfully the fatigue life of full diameter CFRP pipes, using stresses computed at critical locations in the CFRP pipe.     

Brittle failure caused by lamellar splitting in a large-scale tubular joint with fatigue cracks

This paper reports a new incidence of brittle failure by lamellar splitting in a large-scale tubular X-joint and examines the possible causes of this failure. The X-joint, with multiple pre-existing fatigue cracks at the weld toe along the brace-to-chord intersection, experiences brittle failure during a monotonic in-plane bending test. Post-test sectioning of the material around the brace-to-chord intersection reveals lamellar splitting in the mid-thickness of the chord wall instead of rapid extensions of the fatigue cracks in the through-thickness direction. The lamellar splitting observed in this test differs from the conventional lamellar tearing both in its appearance and in its causes. The elongated nonmetallic inclusions concentrated at the mid-thickness, as revealed by the microscopic scanning, leads to delamination cracking near the mid-thickness and subsequently to the brittle failure of the joint. The material requirements in prevailing engineering codes do not suffice to prohibit the lamellar splitting failure observed in this study, which may cause catastrophic failures in engineering structures designed with insufficient redundancy.     

功能结构发动机机体的弹性半解析研究

用功能材料结构来制造发动机机体是使车辆功能轻量化和提高技术含量的关键方法,本文利用半解析广义双重傅立叶级数解法对汽车功能材料结构发动机机体进行了分层剪切研究和数值分析。通过机体的动态特性试验,获得了机体所受复杂载荷下关键部件的应力响应,并用试验验证计算结果。从而证实了功能结构发动机机体的优越性,并为功能结构机体的优化设计奠定了基础。     

Mode Mixity for Orthotropic Interface Delamination in Laminated Composites

The mode mixity is defined based on nonoscillatory strain energy release rate components of delamination between two different orthotropic materials to evaluate the delamination behavior of laminated composites.The result showes that the relative location of the delamination through the thickness influences the mode mixity in a relatively well-regulated way,and that the reinforcement directions of the adjacent plies along the delamination front have a more complicated impact on the mode mixity.This is caused by the bending/twist coupling and bending/bending coupling in the stress field at the crack tip for delamination between multidirectional plies,which completely modifies the stress and strain fields ahead of the crack tip.These kinds of couplings account for the non-uniform distribution of mode mixity values along the delamination front.Application of appropriate mode mixity values is necessary for accurate prediction of delamination growth.     

基于支持向量机的船舶柴油机层次故障诊断的研究

文章介绍了支持向量机的原理和算法,分析了层次分析法及其在故障诊断中的应用,并在上述理论下,建立了柴油机的故障模型。仿真结果表明,SVM能够在小样本的情况下解决柴油机故障诊断的分类问题,在实际的机械故障诊断的分类中具有广泛的应用前景．