A micromechanical model for bioinspired nanocomposites with interphase, Xia, Geng, Zhang, Wang, Composite Structures, 2023
Novelty/Impact/Significance/Breakthrough:
Address directly the interphase in the bioinspired stagger-aligned nanocomposite through establishing a new analytical micromechanical model, which exhibits superior accuracy and simplicity as well as general applicability.
The derived compact formula of effective modulus shows explicitly the influencing trend of the interphase (which is dependent on parameters of the reinforcement and the matrix) and reveals working mechanisms of the interphase (significantly affects the effective modulus when the interphase undertakes both stress-transfer and stress-sustaining roles). These provide new insights in designing/optimizing bioinspired nanocomposites through modulating the interphase properties.
Scientific question:
For the practically important but rarely-recognized interphase (as an independent constituent having a thickness) in the bioinspired stagger-aligned nanocomposite, what is the analytical, quantitative relation between the interphase properties and the overall elastic mechanical properties?
Key of how:
(i) To derive a compact formula of the effective modulus explicitly showing effects of the interphase properties, the staggered platelet-interphase-matrix structure model is constructed and the classical shear-lag theory with necessary assumptions is adopted. Moreover, a careful observation finding certain symmetry and consistency of some equations and corresponding artful operations to simplify the calculation and formulae are indispensable. (This three-phase staggered structure is more complex than two-phase, staggered platelet-matrix structure, but the derived solution of effective modulus is simpler with decent efficacy.)
(ii) Comparison to finite element analysis results and existing relevant models validates the notable simplicity and accuracy over wide ranges of interphase properties, which lie in thoroughly including important geometrical features and properly approximating the shear behaviors of the interphase and the matrix.
(iii) To explore and reveal the working mechanisms of the interphase, not only analyzing the influencing trend, but also (i) exploring variations of the interphase tensile and shear stresses and (ii) comparing with the classical tension-shear-chain model predictions are conducted to elucidate the nature/mechanical role of the interphase in affecting the overall effective modulus.
Plot/Layout:
Bioinspired stagger-aligned nanocomposite structure is successful as seen by many developed bioinspired strong and tough composites
→ One key feature is interphase as (i) in general the interphase essentially affects composite material mechanical properties and (ii) for nanocomposites both the interphase and the reinforcement are at nanoscale, so the interphase should be considered as an independent phase rather than a mathematical interface
→ But mechanics and analysis on interphase containing-staggered nanocomposites remain scarce (existing studies include tension-shear-chain model and related models and shear-lag theory based models)
→ Not yet know how the interphase behaves within the staggered nanocomposite structure and how to enhance/optimize the overall mechanical performance through modulating the interphase properties.
→ This work consists of model derivation, model validation, results and discussion, and conclusions, which hopefully addresses the aforementioned gap to a certain degree and stimulate more future meaningful studies.
Major points:
1. Background and motivation (scarce knowledge on the important interphase effects
within the well-known, successful stagger-aligned nanocomposite structure).
2. Derivation: (i) construct the staggered platelet-interphase-matrix structure model, (ii) divide into three regions horizontally and five zones transversely so as to perform force analysis respectively and formulate appropriate equations for each region best fitting the local interactions, then combine each through continuity assumptions, (iii) find certain symmetries and consistencies among the complex equations to simplify the final solution of the effective modulus formula.
3. Validate the analytical model through comparisons with finite element analysis results and predictions of other existing relevant models.
4. Analyze the influence of the interphase properties on the effective modulus (keeping parameters of the matrix and the platelet constant):
The effective modulus as a function of interphase modulus (platelet aspect ratio changes)
The effective modulus as a function of the interphase thickness (platelet aspect ratio changes)
5. Explore working mechanisms of the interphase:
(5.1) The interphase normal stress and shear stress v.s. interphase modulus
The interphase normal stress and shear stress v.s. interphase thickness
(5.2) Observing the predictions of the derived formula of effective modulus and comparing with those of the expanded tension-shear-chain model.
Here is the link of the fulltext, which is 48-day free access/download: https://authors.elsevier.com/a/1hPT-x-7hsBoT