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J. Michael Pereira

Publications and source records attributed to J. Michael Pereira.

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Dynamic Crush Performance of Thermoplastic and Resin Infused Thermoset Triaxially Braided Composite Structures

Dynamic crush tests were conducted on triaxially braided composite tubes and C-channel structural elements to measure their relative energy absorbing characteristics. The elements were manufactured from triaxially braided [0/+60/-60] T700 fiber preforms with two different resin systems, a PR520 thermoset resin and a LM-PAEK thermoplastic resin. T700/PR520 composite tubes and C-channel elements were manufactured using a resin infusion process. T700GC/LMPAEK composite tubes were manufactured by braiding slit tape prepreg onto cylindrical mandrels. Consolidation pressure was applied through thermally activated shrink tape in an oven. The energy absorbing characteristics of the composite elements were measured using a pneumatically actuated sled with a flat-faced impacting mass, which provided several independent measurements of force, displacement, and energy absorption. The parameter primarily used for comparison between the systems was the specific energy absorption (SEA), a measure of energy absorbed per unit crushed length. The T700/LMPAEK tubes performed slightly better than T700/PR520 tubes, with an approximately 9% higher SEA. T700/PR520 tubes had over 20% higher SEA than C-channels made from the same material. Additional tests were conducted on tubes using a tapered-conical impactor to force the tubes to fail in circumferential tension. This type of impact significantly reduced the energy absorption.

Composite Materials↗
NASA NTRS2023

Experimental Tests to Characterize the Behavior and Properties of IM7-8552 Composite

This document summarizes the test procedures for characterizing the quasi-static (QS), room temperature (RT) behavior of IM7/8552 unidirectional composite material. All testing reported in this document follow applicable ASTM1 test standards as closely as possible, with any deviations reported. The overall objective is to develop a framework for the creation of MAT213 material input for use in the LS-DYNA program (LSTC, 2016). Details of the MAT213 material model and its implementation are available publicly (Goldberg et al., 2015; Harrington et al., 2016; Hoffarth et al., 2016). However, the measured properties can be utilized by most composite impact models.

Mechanical Properties↗
NASA NTRS2021

Numerical Validation of Composite Panel Impact Tests

Researchers have met the challenge of modeling impact events involving composite targets for a variety of applications in a variety of ways. In this paper, the theory and implementation details of an orthotropic visco-elastic-visco-plastic material model with strain rate dependence are discussed. The model is driven by experimental data from quasi-static as well as high strain rate tests, and the data is used in defining the deformation, damage and failure sub-models. Validation data is generated by shooting a hollow 50 g Al-2024 projectile at different velocities against a flat panel target made of unidirectional composite material in a 16-ply [(0/90/45/-45)_(2)]_(S) layup. Explicit dynamic finite element analyses of four high speed tests involving one contained (projectile rebounded) and three uncontained (projectile penetrated) impact tests show that the developed material model and modeling techniques yield reasonable and acceptable predictions.

Orthotropic Composite↗
NASA NTRSDate not supplied

Experimental Evaluation of Axial Crush Behavior of Woven Tubular Laminates with a Moving Support Condition

The objectives of the investigation were to measure the specific energy absorption (SEA) of the plain-weave carbon fiber reinforced polymer (CFRP) tubes, study the effect of tube length on SEA and stable crushing force, analyze the effect of using a crush trigger, and compare force-displacement data using different specimen support conditions. Dynamic crush testing of CFRP tubes was performed using the crash sled in the Impact Dynamics Laboratory at NASA Glenn Research Center.

Rudy T. Haluza↗
NASA NTRSDate not supplied

Crash Sled Testing of Triaxially-Braided CFRP for Improved Vehicular Crashworthiness

The Impact Dynamics Laboratory at NASA Glenn Research Center recently developed a pneumatically-actuated crash sled for investigating the crush behavior of structural elements for vehicular applications. The apparatus includes an adjustable striker mass and specimen support mass, which are mounted on separate rails. This setup provides two advantages over crash sleds with so-called fixed specimen supports: (i) it allows for multiple independent measurements of the crush response using different instruments, and (ii) the specimen support can be varied and its reaction can be explicitly measured. This paper describes the experimental setup and data analysis methodology and illustrates the capability of the sled for measuring the specific energy absorption (SEA) of triaxially-braided carbon/epoxy composite C-channels and corrugated plates. The corrugated plate had a higher SEA than the C-channel and the SEAs did not vary when the striker mass and velocity were changed so that incident energy was constant.

Energy absorption↗
NASA NTRSDate not supplied

Simulation of Dynamic Crushing Behavior of Simulated Carbon/Epoxy Stanchions Using MAT58 and MAT213 in LS-DYNA

Carbon fiber-reinforced polymer (CFRP) composites have shown promise as a material for structures designed to absorb energy in crush-style impact loading. In complementing the lightweight and tailorable characteristics of CFRP structures, the benefits of impact energy absorption are particularly interesting in aerospace vehicles that require excellent crashworthiness performance. However, simulating the behavior of CFRP structures in dynamic, crushing-style impact loading is challenging because of the many damage and failure modes that are essential to capture in the model. For the present investigation, CFRP stanchions were tested using a crash sled experimental test rig. The stanchions were designed by the Composite Materials Handbook-17 (CMH-17) Crashworthiness Working Group for the purpose of comparing experimental crash sled tests to corresponding simulations of the tests. The stanchions are C-channel shaped and represent a geometry common in the interior of aerospace vehicle structures. Explicit simulations in LSDYNA were performed using a well-established composite material model (MAT58) and a next-generation material model (MAT213). Fully integrated shell elements were utilized instead of 3D solid elements to limit computation time. In all models, each of the sixteen plies were represented with individual layers of shell elements with tiebreak contact between each adjacent ply pair to simulate interlaminar fracture. Simulating the crushing of the stanchions occurred in two phases. First, the material models were calibrated using flat specimens that were manufactured with the same layup as the stanchions. While the original goal was calibration of material-related properties, meshdependent behavior was observed in simulations with either material model, and an unstructured mesh was selected to remediate undesirable mesh-dependent failure modes. Additionally, for both the MAT58 and MAT213 models, it was found that either the crush force or the failure mode could be modeled accurately, but no set of parameters could be identified to attain both results in the same model. Once satisfactory calibration was achieved, the same material parameters were applied to the stanchion crush simulations. The stanchion simulations showed that MAT213 more accurately predicted the experimentally determined crush force, and both material models predicted key aspects of the experimentally observed failure modes.

Composite Materials↗
NASA NTRSDate not supplied

Consolidation of Braided Carbon Fiber/ Thermoplastic Tubes by Induction Heating

Thermoplastic composites have experienced renewed enthusiasm within the U.S. aerospace industry, due in part to opportunities for rapidly manufacturing large structures. Unlike the lengthy cure cycles required by thermosets, the thermoplastic matrix prepreg requires only heat and pressure to consolidate consecutive layers of material; with sufficient inter-ply contact time to develop a strong interface. The manufacturing requirements for thermoplastics provide manufacturing flexibility and of particular interest are in-situ consolidation processes; i.e consolidation during layup on a tool. In-situ consolidation removes the time-consuming and costly secondary processing step of autoclave or press consolidation. Process variables which contribute to laminate quality include temperature, heat transfer, inter-ply contact time, and consolidation pressure. Most of the work to date related to in-situ consolidation has been in conjunction with automated fiber placement (AFP), where prepreg tows are consolidated when placed on the tool. Considering this process for a braided structure adds complexity relative to AFP due to the rapid lay-down rate of the braider and simultaneous placement of a multiple prepreg tows. Processes considered for consolidation during AFP could not be applied to a braided part. Alternatively, a fully braided preform could be consolidated on the tool using well established thermoplastic welding techniques. The goal of this effort was to evaluate the effectiveness of induction welding to consolidate braided carbon fiber/thermoplastic composite tubes up to eight plies in thickness. The manufacturing process, thermal characterization, and initial mechanical property data of the consolidated tubes are reported.

In-situ consolidation, induction heating/welding, ↗