Structure-property relationships from universal signatures of plasticity in disordered solids

When deformed beyond their elastic limits, crystalline solids flow plastically via particle rearrangements localized around structural defects. Disordered solids also flow, but without obvious structural defects. We link structure to plasticity in disordered solids via a microscopic structural quantity, “softness,” designed by machine learning to be maximally predictive of rearrangements. Experimental results and computations enabled us to measure the spatial correlations and strain response of softness, as well as two measures of plasticity: the size of rearrangements and the yield strain. All four quantities maintained remarkable commonality in their values for disordered packings of objects ranging from atoms to grains, spanning seven orders of magnitude in diameter and 13 orders of magnitude in elastic modulus. These commonalities link the spatial correlations and strain response of softness to rearrangement size and yield strain, respectively

An Optimization Strategy Based on Machine Learning and LayerWise Models to Minimize Process-Induced Deformations in CFRP Parts

Virtual manufacturing of composites has become increasingly important over the last two decades as a tool to improve the quality and sustainability of composite structures. However, the manufacturing process simulation is complex and multidisciplinary and may require high computational overheads. This paper aims to the virtual curing of composite parts and use machine learning techniques to optimize the stacking sequence and minimize process-induced deformations. Such a methodology combines 1D finite element (FE) models, experimental testing, and machine learning models. The FE model exploits higher-order layer-wise theories to compute accurate through-the-thickness distributions of shear and peeling stresses. 1D elements lead to better efficiency by requiring a fraction of the computational cost usually needed by 3D finite element models. DSC and DMA tests characterize relevant material properties, e.g., the degree of cure, viscoelastic moduli, and free strains. Furthermore, a cure-hardening instantaneously linear elastic (CHILE) constitutive model is adopted. The FE model allows the rapid evaluation of residual stresses, spring-in angles, and warpage. Due to its numerical efficiency, various lay-up combinations can be evaluated, and the results can feed a dataset to train an Artificial Intelligence system. This study uses Gaussian process regression (GPR) to fit probabilistic response surfaces to numerical deformation predictions, explore the design space, and find optimal lay-ups minimizing defects. Furthermore, mitigation strategies are developed using specific lay-ups around geometry transition points such as sharp corners. Finally, optimal lay-ups are validated by fabricating L-shaped parts with similar conditions

OPTIMAL LAY-UPS TO MINIMIZE PROCESS-INDUCED DEFORMATIONS IN L-SHAPED CFRP PARTS

This paper presents results concerning the mitigation of process-induced deformations in composite parts. The focus is on combining numerical models based on finite elements and experimental testing to propose specific lay-ups around geometry transition points, such as sharp corners, to minimize process-induced deformations such as spring-in angle and warpage. The numerical model is based on higher-order layer-wise 1D finite elements providing very accurate through-the-thickness distributions of shear and peeling stresses. Such a numerical approach requires a fraction of the computational cost usually needed by 3D finite element models. Evolution of material properties such as degree of cure, viscoelastic moduli, and free strains are characterized using DSC and DMA tests. Accordingly, a cure-hardening instantaneously linear elastic (CHILE) constitutive model is adopted for numerical simulations. Simulation results and proposed optimal lay-ups are validated by fabricating L-shape parts with similar conditions

Vorbereitung und Durchfuehrung eines Versuchs zur Loesungszonenkristallzuechtung von Cadmiumtellurid waehrend der FSLP-Spacelab-Mission Schlussbericht. Abschlussdatum: September 1984

TIB: RA 674 (86-005) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Reliability of interfaces in newly designed ceramic-ceramic and metal-ceramic systems Brite final report

SIGLEAvailable from TIB Hannover: RN 1909(1990,3) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Vorbereitung eines Versuchs zur Loesungszonenkristallzuechtung von Cadmiumtellurid waehrend der FSLP Spacelab-Mission

SIGLEDEGerman

Experimentelle Untersuchung des Einflusses von Rissfeldern auf mechanische und bruchmechanische Groessen Abschlussbericht

With 3 tabs., 12 figs., 7 refs.Available from TIB Hannover: RN 1909(1990,8) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman