This study explores the application of Convolutional Neural Networks (CNN) in predicting the partitioned homogeneous properties (PHPs) of electronic product wiring structures, aiming to enhance the efficiency of reliability analysis through Finite Element Analysis (FEA). A systematic and novel method was developed to generate the input partitioned wiring diagram image sets that foster model generalization and universality. The performance of the CNN-based approach was assessed through regression analysis by employing a leave-one-out cross-validation (LOOCV) approach across three PCBs. Additionally, the predicted PHPs of one of the PCBs were applied in product-level FEA to validate their reliability, further demonstrating the practical applicability of the CNN-based method. The results demonstrate that a well-trained CNN model can accurately predict the properties of previously unencountered wiring structures, thereby facilitating direct application in product-level reliability FEA and improving the efficiency of reliability assessment. Furthermore, efficiency evaluation revealed that the CNN-based method offers significant advantages in terms of time and cost economy compared to the mesoscopic FEA method in determining, highlighting its potential for broader application in electronic product reliability analysis. The findings provide preliminary insights and propose strategies to enhance the applicability of CNN methods in this domain, ultimately aiming to improve the efficiency and reduce costs in reliability assessments, thereby streamlining the overall product development process.

This study introduces a cross-scale numerical analysis approach for modeling the lamination process and predicting the post-lamination warping deformation of Printed Circuit Boards (PCBs), utilizing the partitioned homogenization methodology to account for the mesoscopic structure of each conductive layer. The curing reaction and viscoelastic properties of the resin are also taken into account and an investigation on the partitioned homogenization methodology of the resin's curing-induced shrinkage effect is conducted. Furthermore, an innovative partitioned homogenization method to deal with the non-uniform curing shrinkage effect of the conductive layers is proposed in this paper, by assigning the calculated homogenized curing shrinkage strain of conductive layers to their adjacent prepreg layers. When aligned with experimental data on the temperature distribution and evolution during lamination and the post-lamination warping deformation, the numerical predictions are found to be accurate. This affirms that the proposed approach emerges as an accurate predictor of PCB post-lamination warping deformation, thereby enhancing the design efficiency and quality of reliability analysis. Additionally, the proposed approach shows promise for broad application in microelectronics where addressing non-mechanical strains in conductive layers is crucial.

The increasing prevalence of reliability issues related to printed circuit boards (PCBs) has led to significant interest in applying finite element analysis (FEA) for PCBs. This study presents an equivalent property algorithm based on the mesoscale finite element method (FEM), which took into account the intricate structural features of conductive layers in PCBs. Additionally, a series of automated scripts were developed to streamline the modeling and calculating process, markedly enhancing the accuracy and efficiency of equivalent modeling and simulation of the PCB. Based on the proposed algorithm, a multiscale three-point bending finite element model of a PCB was established. By comparing the results to experimental data from three-point bending tests, it was demonstrated that the stress field simulated using the proposed algorithm accurately represented the anisotropic properties of the intricate copper traces in the conductive layers, leading to more accurate predictions of mechanical responses than those obtained using conventional algorithms. Furthermore, the research on the impact of partition size on both simulation accuracy and computational efficiency clearly demonstrated that partition size significantly affected these aspects. In conclusion, the proposed algorithm provided a more reliable and efficient approach for applying FEA and FEM to PCBs, contributing to advancements in the field of PCB analysis and fostering improvements in electronics design and manufacturing.

Carbon fiber reinforced polymers (CFRPs) will exhibit complex coupling responses accompanied by multi-physical damages under the strike of lightning, which makes CFRP-intensive structures have serious safety hazards when applied in the fields of aerospace and wind turbine blades. To accomplish the mechanical simulation of CFRPs under the lightning effects of thermal stress and impact, it is crucial to consider both the thermal and mechanical factors together in the damage constitutive model. In this study, based on the continuum damage mechanics and phenomenological theory, a lightning damage variable that considering the combined contributions of both pyrolytic and mechanical factors to the lightning damages of CFRPs was introduced. On this basis, a pyrolysis-affected damage constitutive model was established to describe the intra-/inter-laminar damage behaviors of CFRPs caused by lightning. Furthermore, sequential coupling of electrical-thermal-pyrolytic and thermal-pyrolytic-mechanical analysis steps was conducted by ABAQUS in accordance with the experiment. The results revealed that the influence of pyrolysis on the degradation of mechanical properties played a noticeable role in the dynamic response and intra-laminar damage of CFRP laminates. In addition, the delamination originating from lightning thermal stress and shockwave overpressure was significant but gradually covered by pyrolytic damage. Still, a big gap existed between the simulated and experimentally detected damages due to the explosion of pyrolytic gas during lightning.

ABSTRACTA new numerical simulation method was proposed to predict the mechanical behavior of carbon fiber reinforced resin composites under low‐velocity impact load. The impact damage evolution can be characterized in the form of energy dissipation which can be calculated through the new numerical model. The evolution mechanism of delamination was analyzed through distinguishing between the normal induced delamination and tangential slip induced delamination. The drop weight tests were conducted on composite laminates with five kinds of stacking sequence. Experimental analysis was also presented in this article. The damage area and distribution was investigated through ultrasonic C‐scan. The prediction had a good agreement with the experimental results through the comparison of impact response. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44374.

Based on the continuum damage mechanics (CDM) and the cohesive zone model (CZM), a numerical analysis method for the evaluation of damage in composite laminates under low‐velocity impact is proposed. The intraply damage including matrix crack and fiber fracture is represented by the CDM which takes into account the progressive failure behavior in the ply, using the damage variable to describe the intraply damage state. The delamination is characterized by a special contact law including the CZM which takes into account the normal crack and the tangential slip. The effect of the interlaminar toughness on the impact damage is investigated, which is as yet seldom discussed in detail. The results reveal that as the interlaminar fracture toughness enhances, the delamination area and the dissipated energy caused by delamination decrease. The contribution of normal crack and tangential slip to delamination is evaluated numerically, and the later one is the dominant delamination type during the impact process. Meanwhile, the numerical prediction has a good agreement with the experimental results. The study is helpful for the optimal design and application of composite laminates, especially for the design of interlaminar toughness according to certain requirements. POLYM. COMPOS. 37:1085–1092, 2016. © 2014 Society of Plastics Engineers

The objective of this research is to put forward a toughening method by using the polyamide non-woven fabric (PNF) and investigate the Mode-I fracture toughness and delamination characteristic of the toughened CFRP laminates by performing the double cantilever beam test. The effect of PNF interlayer, which is formulated by a bilinear cohesive zone model, on the Mode-I fracture of U3160-PNF/3266 laminated composites is numerically analyzed. And the intralaminar damages are considered by using strength criteria and stiffness degradation law. The influences of PNF/3266 interlayer strength, U3160/3266 laminate thickness and initial crack length on the mechanical response of laminates are studied systematically. The work by combining the experiment and simulation is helpful for the optimal design of laminated composites used in aerospace and civil engineering.

The high Joule heating of carbon fiber reinforced polymer composites (CFRP) subjected to lightning strike induces resin decomposition and carbon sublimation. The mechanism and characteristics of the change in composite material properties are the key basis of the numerical analysis and the optimal design of composite structures. In order to elucidate the damage phenomena caused by lightning strike, a tightly coupled electrical-thermal-pyrolytic analysis is conducted by introducing the numerical calculation of resin pyrolysis degree on the basis of thermal-electrical numerical analysis. Hence the electrical and thermal properties in both out-plane and in-plane directions are modeled as functions of the pyrolysis degree of the composite material, namely the material properties change with the component during the decomposition, which is revealed to be reasonable from both the numerical and the experimental results. The research is helpful for understanding the complicated relationships in the important damage process including electrical, thermal and chemical phenomena.

A resin transfer molding technique was used to fabricate thick-walled composite connecting rods, and then the mechanical performance of the connecting rod was studied experimentally, at the same time the stress and failure index distributions were simulated numerically. The experimental results show that under a tensile load, the connecting rod first cracks near the vertex of the triangle areas at the two ends, and then the damage propagates along the interface between the main bearing beam and the triangle area as well as along the round angle of the triangle area. Whereas under a compressive load, the delamination primarily occurs at the corner of the U-shaped flange, and the final destruction is caused by the fracture of fibers in the main bearing beam. The simulated results reveal that the tensile failure is originated from the delamination at the round angle transition areas of the T-joints, and the failure strength is determined by the interlaminar strength. Whereas the compressive failure is caused by the fracture of fibers in the main bearing beam, and the failure strength of the structure is determined by the longitudinal compressive strength of the composite material. The simulated results are basically consistent with the experimental results. Hence the mechanical performance and failure mechanism of the complicated composite structure are revealed in great detail through the coupling of the two kinds of research methods, which is helpful for the optimal design of composite structures.

The intralaminar and interlaminar damages of U3160/3266 laminated composites toughened by polyamide nonwoven fabric (PNF) under low velocity impact are investigated through a numerical model which considers both the three‐dimensional continuum damage mechanics (CDM) and the bilinear cohesive zone model (CZM). The analysis of the intralaminar damage is implemented by the ABAQUS/Explicit finite element code coupled with a user‐defined subroutine VUMAT where the longitudinal failure, transverse matrix cracking, and nonlinear shear of the material are taken into account. Then the effects of the thickness and strength of PNF/3266 interlayer on the damage of composites are numerically analyzed. The results reveal that damage morphology can be simulated qualitatively compared to the experimental counterparts. With the decreasing interlayer thickness or the increasing interlayer strength, the damage area is effectively reduced. This work provides an effective model to predict the low velocity impact damage of composites, and is helpful for the optimization of interlayer toughened composites. POLYM. COMPOS., 38:1280–1291, 2017. © 2015 Society of Plastics Engineers

A constitutive model is constructed to consider the resin matrix post-yield softening and progressive hardening behaviors. A user-defined material mechanical behavior (UMAT) subroutine is created, then the non-linear three-dimensional finite element analysis on the tensile processes of multi-fiber composites is conducted. The approximate 45° shear bands emanating from the matrix crack tip are found, being coincided with the experimental observations. The shear stress on the adjacent intact fiber/matrix interface is strongly influenced by the shear band and thus the stress concentration factor (SCF) changes obviously in the adjacent fibers. The distinct stress redistribution in the adjacent intact fibers implies the significant effect of the shear bands on the progressive fiber fracture initiation. As the inter-fiber spacing increases, the peak value of the SCF in the adjacent intact fiber decreases, whereas the overload zone becomes wider. The research has provided a helpful tool to evaluate the failure of fiber composites and optimize the composite performance through the proper selection of resin matrix properties and fiber volume fraction.

On the smallest structural scale in the multi-scale structure composites, namely fiber scale, a numerical model was proposed for the analysis on the mechanical properties of unidirectional composites through the representative unit cell (RUC). The progressive method was used to simulate the failure behavior of fiber and matrix, and the debonding between fiber and matrix was characterized by the cohesive zone model (CZM). The failure strength of the unidirectional composite was predicted, and the influence of the interfacial strength on the mechanical behavior of unidirectional composite was discussed. It is shown that fiber dominates the failure strength of the material under the longitudinal load, whereas under the transverse load interfacial properties play an important role in the mechanical behavior of the material. The increase of the interfacial strength can significantly improve the capability of transverse compression and shear resistance.