The Structural Integrity of Composite Materials and Long-Life Implementation of Composite Structures
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The Structural Integrity of Composite Materials and Long-Life Implementation of Composite Structures Peter W. R. Beaumont 1 Received: 6 May 2020 / Accepted: 18 June 2020/ # The Author(s) 2020
Abstract
Empirical or semi-empirical design methodologies at the macroscopic scale (structural level) can be supported and justified only by a fundamental understanding at the lower (microscopic) size scale through the physical model. Today structural integrity (SI) is thought as the optimisation of microstructure by controlling processing coupled with intelligent manufacturing of the material: to maximise mechanical performance and ensure reliability of the large scale structure; and to avoid calamity and misfortune. SI analysis provides quantitative input to the formulation of an appropriately balanced response to the problem. This article demonstrates that at the heart of the matter are those mechanisms of crack nucleation and growth that affect the structural integrity of the material: microscopic cracking events that are usually too small to observe and viewed only by microscopy. Keywords Composite materials . Structural integrity . Cracking and fracture . Physical modelling methods and analyses . Lifetime prediction . Structural health monitoring
1 Background In critical engineering conditions of variable stress-state, fluctuating temperature and hostile environment, where the objective is to design large composite structures for longevity, durability and reliability out of materials having structural integrity, then the balance between empirical engineering design based on continuum and mathematical modelling, (sometimes called “distilled empiricism”), and physical modelling, (sometimes called “mechanism modelling” or simply “micro-mechanics”), is shifted in favour of physical modelling. Whilst many ancient temples and cathedrals have stood the test of time, others collapsed prematurely without warning leaving the stone mason with head in hands. History is littered with structural disasters where the crucial failure event eluded the experimentalist. Yet despite an acquisition
* Peter W. R. Beaumont [email protected]
1
Engineering Department, Cambridge University, Cambridge, England CB2 1PZ, UK
Applied Composite Materials
of vast collections of experimental data, information and compelling evidence, and an engineer’s intuition based on “feel”, − experience coupled with intelligent observation - a phenomenology - our ability to fully understand that longstanding problem of structural failure remains unresolved. Empirical “rules” simply do not have the power of prediction.
1.1 The Traditional Route of Engineering Design Traditional empirical design formulations have not done well dealing with these challenges. Successful prediction of mechanical behaviour of material and design life of a structure requires detailed information of all possible failure mechanisms across the widest spectrum of size-scale under all sorts of operational conditions. To set up an experimental program that covers all eventualities
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