【摘要】：復合材料加筋壁板結構是航空航天復合材料結構中應用非常廣泛的一種典型結構,其中筋條和蒙皮的脫粘是主要的損傷形式。Z-pin增強技術作為一種適用于預浸料成形復合材料的層間增強技術,可用于加筋壁板結構連接界面的增強。本文在Z-pin增強T型加筋結構制備工藝試驗的基礎上,針對復合材料T型加筋結構的界面連接性能,開展試驗研究和數(shù)值分析,研究參數(shù)對結構承載力的影響規(guī)律及Z-pin增強機理,為Z-pin在復合材料加筋結構增強中的實際應用提供指導及參考。(1)研究Z-pin增強T型加筋結構試樣的成型工藝,并對工藝進行改進。設計制作專用成型模具,進行熱壓罐固化成型。結果表明,利用增加模具突緣厚度、增大筋條拐角半徑、增加拐角區(qū)的填充量等方法,可以解決Z-pin不能完全穿透預浸料坯料、填充區(qū)不密實等問題,有效改善試件的成型質量。(2)通過面外拉伸試驗和剪切試驗表征T型加筋結構筋條-蒙皮間的連接性能,并研究Z-pin對加筋結構的增強機理。研究表明,Z-pin對T型加筋結構的初始載荷沒有影響,但能提高極限載荷及殘余載荷;隨著加載過程,Z-pin受力狀況由純I型方向層間應力逐漸轉變?yōu)镮/II型方向混合應力,導致Z-pin發(fā)生側向擠壓,這一過程對Z-pin的增強效果有強化作用。剪切試驗發(fā)現(xiàn),試樣筋條和蒙皮發(fā)生瞬間分離破壞,Z-pin明顯提高初始載荷,但對試樣掉載后殘余承載能力的作用不明顯。(3)研究Z-pin體積含量對T型加筋結構拉伸承載力的影響規(guī)律,在此基礎上研究Z-pin對含損傷T型加筋結構的增強作用,并進一步研究突緣長度對Z-pin增強效果的影響。Z-pin含量對比試驗結果表明,T型加筋結構拉伸承載力隨Z-pin含量增加而先上升后下降,Z-pin可使極限載荷的提高高達70.4%。預制缺陷試驗結果表明,對于T型接頭中占粘結面10%~30%尺度的層間缺陷,Z-pin橋聯(lián)作用能實現(xiàn)對結構承載能力較大程度的保持,將相同尺度缺陷空白T型接頭的極限載荷提高90%以上。突緣試驗結果表明,試樣的失效形式隨突緣長度增加發(fā)生轉變;Z-pin植入后,T型接頭的最優(yōu)突緣長度由60mm降低為40mm,對結構減重有重要意義。(4)借助估算法確定界面剛度和強度的取值,并利用能量差值平均化方法對現(xiàn)有的Z-pin增強等效方法進行改進,采用分區(qū)內聚力模型建立Z-pin增強T型加筋結構的二維數(shù)值模型。以此為基礎,利用該模型對不同約束跨距、蒙皮厚度的T型加筋結構拉伸承載力進行分析。結果表明,在試驗范圍內,隨著跨距增大或蒙皮厚度減小,筋條-蒙皮連接界面拉剪應力比值減小,Z-pin由拔脫失效轉變?yōu)榘蚊?斷裂混合失效,Z-pin增強T型接頭的拉伸承載力下降。
[Abstract]:Composite stiffened panel structure is a typical structure widely used in aerospace composite structure. The debonding of tendons and skin is the main damage form. Z-pin reinforcement is a kind of interlaminar strengthening technology suitable for prepreg forming composite materials. It can be used to strengthen the interface of stiffened panels. In this paper, based on the experimental results of Z-pin reinforced T-reinforced structures, the experimental study and numerical analysis are carried out to study the influence of parameters on the bearing capacity of T-reinforced composite structures and the mechanism of Z-pin reinforcement, aiming at the interfacial bonding properties of T-reinforced composite structures. It provides guidance and reference for the practical application of Z-pin in reinforced composite structure. (1) the forming process of Z-pin reinforced T-reinforced structure specimen is studied and the process is improved. Design and manufacture special moulds to solidify the hot-pressed tank. The results show that by increasing the thickness of the die edge, increasing the corner radius of the bar and increasing the filling amount of the corner area, the problems of Z-pin can not penetrate the blank of prepreg completely and the filling area is not dense, etc. (2) the tensile test and shear test were used to characterize the bonding properties of T-type reinforced structure between the stiffened strip and the skin, and the reinforcement mechanism of the reinforced structure by Z-pin was studied. The results show that Z-pin has no effect on the initial load of T-type reinforced structure, but it can increase the limit load and residual load, and with the process of loading, the interlaminar stress in the direction of pure I-type is gradually changed to the mixed stress in the direction of I/II. The lateral extrusion of Z-pin results in the enhancement of Z-pin by this process. The results of shear test show that the breaking of the strip and the skin increases the initial load obviously, but the effect on the residual bearing capacity of the specimen is not obvious. (3) the effect of the volume content of Z-pin on the tensile capacity of T-reinforced structure is studied. On this basis, the enhancement effect of Z-pin on T-stiffened structures with damage was studied. Furthermore, the effect of edge length on the strength of Z-pin was studied. The results showed that the tensile capacity of T-type reinforced structure increased first and then decreased with the increase of Z-pin content, and the ultimate load increased as high as 70.4%. The experimental results of prefabricated defects show that for T-joints with 10% or 30% of bonding surface, Z-pin bridging can maintain the bearing capacity of the structure to a large extent, and increase the limit load of blank T-joints with the same size defects by more than 90%. The results of edge test show that the failure form of the specimen changes with the length of the edge. The optimum edge length of T-joint is reduced from 60mm to 40mm after Z-pin implantation. (4) the value of interface stiffness and strength is determined by means of estimating method. The energy difference averaging method is used to improve the existing Z-pin enhancement equivalent method, and the two-dimensional numerical model of Z-pin reinforced T-stiffened structure is established by using the zone cohesion model. Based on this model, the tensile capacity of T-type reinforced structures with different restrained span and skin thickness is analyzed. The results show that in the range of test, with the increase of span or the decrease of skin thickness, the ratio of tensile shear stress at the interface of stiffened strip and skin decreases from pull-out failure to mixed pull-out / fracture failure. The tensile strength of T-joint reinforced by Z-pin decreases.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB33

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本文編號：2231974