缺陷对纤维金属层板低速冲击性能影响规律

为研究不同孔洞大小和位置的玻璃纤维铝合金层板抗冲击性能损伤规律,本文通过在Abaqus中建立落锤低速冲击有限元模型,分析了玻璃纤维铝合金层板受冲击后的接触力、能量吸收、试件变形的响应规律。该模型中用自定义子程序VUMAT、Johnson-Cook金属损伤模型以及基于接触行为的表面内聚力行为分别可以用于分析复合材料、铝合金层和层间分层行为。在20 J冲击能量下,对比分析了圆孔大小和圆孔位置对玻璃纤维铝合金层板材料的冲击响应和破坏规律。结果表明:固定半径2 mm,圆孔距离玻璃纤维铝合金层板中心处较近的试件铝合金层板损伤、层间损伤、复合材料板损伤范围大,且集中于圆孔内侧;固定圆孔距离冲击中心为6 mm,随孔径增大,试件的各类损伤集中于缺陷周围。因此,缺陷会明显降低玻璃纤维铝合金层板的抗冲击性能。

飞机蒙皮用纤维金属层合板基体2024-T3铝合金薄板研究

利用金相显微镜、SEM、拉伸试验机、便携式粗糙度仪,研究了飞机蒙皮用纤维金属层合板基体2024-T3铝合金薄板。结果表明:2024铝合金的线膨胀系数和毛化后的表面粗糙度显著降低。随着自然时效时间的延长,材料的力学性能增大,5 h后趋于稳定,且抗拉强度、屈服强度和伸长率分别可达477、319 MPa和17%。这些参数可避免后期制备层合板时出现分层、纤维脱丝等现象。

低速冲击时冲击角度和摩擦对玻纤增强铝板性能的影响

为了研究在不同冲击角度和接触摩擦力受低速冲击载荷下玻璃纤维铝合金层合板破坏情况,本文结合VUMAT用户自定义子程序、Johnson-Cook损伤模型和基于表面接触行为的内聚力行为方法,建立了玻璃纤维增强铝合金层板(GLARE)低速冲击有限元模型。通过实验对比材料受低速冲击响应和材料损伤状况。结果表明:冲击角较小时材料损伤较小;减小摩擦系数能够减小材料冲击损伤,且减小幅度随着冲击角减小而增大;冲击角度和摩擦对材料冲击性能影响规律可以为类似结构设计提供参考。

Prediction model for determining the optimum operational parameters in laser forming of fiber-reinforced composites

Composite materials are widely employed in various industries,such as aerospace,automobile,and sports equipment,owing to their lightweight and strong structure in comparison with conventional materials.I aser material processing is a rapid technique for performing the various processes on composite materials.In particular,laser forming is a flexible and reliable approach for shaping fiber-metal laminates(FML.s),which are widely used in the aerospace industry due to several advantages,such as high strength and light weight.In this study,a prediction model was developed for determining the optimal laser parameters(power and speed)when forming FML composites.Artificial neural networks(ANNs)were applied to estimate the process outputs(temperature and bending angle)as a result of the modeling process.For this purpose,several ANN models were developed using various strategies.Finally,the achieved results demonstrated the advantage of the models for predicting the optimal operational parameters.

Degradation Behavior of Epoxy Resins in Fibre Metal Laminates Under Thermal Conditions

GLARE （glass fibre/epoxy reinforced aluminum laminate） is a member of the fiber metal laminate （FML） family, and is built up of alternating metal and fiber layers. About 500 m2 GLARE is employed in each Airbus A380 because of the superior mechanical properties over the monolithic Muminum alloys, such as weight reduction, improved damage tolerance and higher ultimate tensile strength. Many tons of new GLARE scraps have been accumulated during the Airbus A380 manufacturing. Moreover, with the increasing plane orders of Airbus A380, more and more end-of-life （EOL） GLARE scrap will be generated after retire of planes within forty years. Thermal processing is a potential method for the material recycling and re-use from GLARE with the aim of environmental protection and economic benefits. The current study indicatdes that thermal delamination is a crucial pre-treatment step for the GLARE recycling. The decomposition behavior of the epoxy resins at elevated temperatures was investigated by using the simultaneous thermal analysis, thermogravimetry analysis （TGA） and differential scanning calorimetry （DSC）. Based on the thermal analysis results, GLARE thermal delamination experiments at refined temperatures were carried out to optimize the treatment temperature and holding time.

玻璃纤维增强铝合金层板高速冲击损伤容限

为研究玻璃纤维增强铝合金(GLARE)层板高速冲击损伤容限,对单次、多次冲击载荷下GLARE层板的损伤特性进行了高速冲击试验和数值仿真研究。采用一级气体炮,在GLARE层板靶板的中心位置、边位置、角位置进行弹道冲击试验,获取弹道极限和损伤模式,然后结合数值仿真剖析动态响应特性。结果表明,弹道冲击条件下,GLARE层板主要通过塑性变形、金属层裂纹、脱胶、复合材料纤维脆断等损伤模式吸收冲击能量。边界约束效应对GLARE层板冲击损伤特性具有显著影响,主要表现在:约束效应导致不同位置冲击下GLARE层板损伤模式不同,包括成坑、金属裂纹和冲塞等特征;角位置冲击条件下,GLARE层板的弹道极限速度明显低于中心位置冲击结果;重复冲击条件下,角位置比与边位置和中心位置更容易发生穿透。