The role of residual stress in the optical quality and stability of replicated composite optics

Ferrelli, Geena L.; Kim, Hyun I.; Zaldivar, Rafael J.

doi:10.1117/12.2628634

Cited by 1 publication

(4 citation statements)

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“…Realistic thermal excursions, such as 1hr at 50°C, degrades the replication surface quality significantly higher than the 0.05λ SFE required for precision UV/Vis space telescopes. The formation of large residual stresses was shown in other work to correspond with stress relaxation over time [11,13].…”

Section: Resultsmentioning

confidence: 54%

“…Since the replication layer is viscoelastic, it is susceptible to stress relaxation where the polymer chains move to relieve internal residual stresses [15]. Due to a combination of high residual stress formation during thermal exposures and the stress relaxation behavior of the replicating epoxy resin, the optical surface will drift over the course of the entire satellite lifetime with a magnitude larger than the 0.05λ SFE allowed for precision applications [13]. Alternative materials or processing must be developed to overcome current thermal instabilities in order to utilize RCO in real satellite missions.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, the glass master can be used an infinite number of times. More details describing this process as well as the critical factors necessary to achieve a high precision mirror have been described in previous publications [9,10,11,12,13].…”

Section: Introductionmentioning

confidence: 99%

“…and then parametric stability studies were performed as a function of time, humidity, and radiation environments. The driving factors of environmental stability were identified, and precision quality and stability were achieved through processing and formulation modifications [9,10,11,12,13].…”

Section: Introductionmentioning

confidence: 99%

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Stress mitigation of replicated composite mirrors via multi-layer replication

Ferrelli,

Kim,

Zaldivar

2023

Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems IV

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Replicated composite optics offer a route to manufacture precision mirrors for satellite applications in a fraction of time and with substantial cost and weight savings over conventional glass mirrors. However, the dimensional stability is a critical barrier to entry for utilizing these mirrors in UV/Vis space applications due to the organic nature of the optical surface and its susceptibly to environmentally-induced distortions that can cause deviations greater than SFE λ/20 (~32nm). Recently, advances in this technology have been achieved at The Aerospace Corporation by using UV cured replicating epoxy resins to produce replicated mirrors with relatively zero residual stress and high hygroscopic stability with RT processing. Elevated thermal stability, though, remains a critical issue as CTE mismatch between the composite and resin lead to residual stress formation which immediately degrades the optical quality and then causes further optical drift over time as stress relaxation occurs. In this paper, we demonstrate improved thermal stability of replicated mirrors by utilizing multiple replication layers where buried compliant layers accumulate residual stress and the top layer is an optimized high modulus resin that achieves a high-quality replication. As a result, thermal stresses incurred by elevated temperatures were reduced by more than 60% when measured via laser interferometry. Additionally, due to faster stress relaxation rates of the compliant layers, the CTE mismatch stress was removed in a matter of days versus years of a conventional single layer replication. This stack-up provides a route to mitigate stress and enhance replication stability.

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Section: Resultsmentioning

confidence: 54%

Section: Resultsmentioning

confidence: 99%