中高应变率下PBX弱界面的粘结性能及损伤本构研究

Failure of explosive crystal/binder imperfect interface has big influence on the dynamic fracture and ignition behavior in polymer bonded explosives(PBX). However, it’s rather hard to lucubrate on the mechanical properties and cohesive models because of its energetic sensibility and compositional complexity, which makes it rather a qualitative interpretation tool, than a high confidence simulation when subjected to fracture or hot spot problems. This project concentrates on the vulnerable tension and shear condition for PBX imperfect interface, and presents a combination method of direct experimental study and numerical inversion. First, typical imperfect interface will be experimentally reproduced by bonding large explosive crystal and binder material contiguously together. The interface samples are then applied for tension and shear testing with a Split Hopkinson tension bar(SHTB), from which the traction-opening displacement relationship would be sufficiently investigated. High speed camera, Digital Image Correlation (DIC) method and fracture surface observation are united in this project, providing an In-situ and Ex-situ combination to clarify the interfacial failure mechanism. On the basis of cohesive theory and taking strain-rate effect and damage effect into account, dynamic cohesive constitutive relations are to be proposed at last. Experimental results will provide partial characteristics such as the critical opening displacement, while the damage evolution law and other constitutive parameters will be determined by micro-mechanical finite element inversion..This research could reference a new mechanical technique for PBX’s interfacial problem, obtain considerable data in its mechanical properties and cohesive models, and provide fundamental supporting for crack initiation pressures and friction factors in PBX crack and ignition related problems.

中高应变率下炸药晶体/粘结剂弱界面失效是高聚物粘结炸药（PBX）动态断裂和异常点火的重要诱因。受含能敏感性和组分复杂性限制，PBX弱界面粘结性能和本构模型等问题一直难以深入，工程应用中常局限于断裂、点火位置的定性分析而很难用于高置信度数值模拟。本项目针对PBX弱界面易破坏的动态拉伸、剪切环境，结合炸药晶体/粘结剂界面的动态试验和数值反演对该问题开展研究。首先利用大颗粒炸药晶体与粘结剂粘结复现PBX中的典型弱界面；开展冲击加载直接获得PBX弱界面在中高应变率下的牵引力-位移关系，同时联合在线-离线形貌观测认识其界面破坏过程；在实验基础上建立含损伤和应变率效应的粘结模型，由动态实验确定临界脱粘位移等参数，并通过细观有限元对损伤演化率和其余参量进行反演。本项目的完成，可增加对PBX弱界面中高应变率失效机理的认识，有助于深入理解炸药断裂、热点形成中的起裂压力和摩擦条件等基础力学问题。

炸药晶体-粘结剂弱界面失效是高聚物粘结炸药（PBX）动态断裂和异常点火的重要诱因，开展PBX弱界面粘结性能和本构模型研究，对于深入理解PBX炸药的环境适应性和贮存有效性具有重要意义。本项目以某奥克托今（HMX）-氟橡胶粘结体系为研究对象，针对PBX弱界面易破坏的拉伸、剪切环境，开展了试验方法、响应行为和本构模型研究。项目组掌握了PBX弱界面模拟试样的制备技术，制备了拉伸型、剪切型弱界面试样，建立了准静态-中高应变率下PBX弱界面试样的直接拉伸和剪切加载与测试方法；开展了不同加载条件下PBX弱界面力学性能研究，获得了PBX弱界面典型的界面应力-位移曲线，观测到了PBX弱界面的破坏过程；认识了PBX弱界面失效的主要特征，发现其力学行为可大致分为三阶段：近似线性上升、非线性下降、零应力流动阶段，其中剪切作用下可能不存在零应力流动段或效应不明显，据此提出了可有效描述PBX弱界面力学响应的界面粘结模型。本项目的研究为PBX弱界面粘结性能和本构模型提供了新的方法，相关认识有助于深入理解炸药断裂、破坏行为，并对炸药配方改性有重要支撑作用。